JP7097588B1 - FM relay device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for suppressing unnecessary waves such as wraparound waves in a relay station of an FM broadcasting system constituting a single frequency network.
A first profile generation unit generates a first delay profile from a result of calculating a time axis correlation between a transmission signal generated by a signal reproduction unit and a reception signal received during a wraparound wave exploration period. .. The second profile generation unit generates a second delay profile from the result of calculating the time axis correlation between the master station signal extracted by the master station wave extraction unit and the received signal received during the multipath wave exploration period. .. The first suppression unit and the second suppression unit generate replica signals of the wraparound wave and the multipath wave according to the delay profile, and subtract the replica signal from the received signal input to the signal generation unit.
[Selection diagram] Fig. 2

Description

The present disclosure relates to a technique for relaying a broadcast wave of an FM broadcasting system.

FM synchronous broadcasting is known in which frequency-modulated audio broadcast waves of the same frequency and the same program are transmitted from a plurality of transmission stations. FM is an abbreviation for frequency modulation. Generally, in a broadcasting system, a relay station is provided to expand the reception area. The relay station used in the existing FM broadcasting constructs a multi-frequency network (MFN). That is, each relay station belonging to the MFN retransmits a broadcast wave (hereinafter, relay wave) having a frequency different from the broadcast wave (hereinafter, master station wave) received from the transmission station serving as the master station.

On the other hand, the relay station used in FM synchronous broadcasting constructs a single frequency network (hereinafter, SFN) using a relay wave having the same frequency as the master station wave. That is, each relay station belonging to SFN retransmits a relay wave having the same frequency as the master station wave. At a relay station belonging to SFN, a wraparound oscillation occurs when a relay wave having a level stronger than that of the master station wave wraps around the receiving antenna, that is, in a so-called minus D / U state, so it is necessary to take measures against the wraparound oscillation.

Patent Document 1 describes a technique for canceling a wraparound wave generated at a relay station in a terrestrial digital broadcasting system that employs SFN.

Japanese Unexamined Patent Publication No. 2009-105834

However, the technique described in Patent Document 1 is premised on terrestrial digital broadcasting using an OFDM signal, and has a problem that it cannot be applied to FM broadcasting of an analog modulation method in which the format of the broadcast signal used is completely different. there were.

One aspect of the present disclosure is to provide a technique for suppressing unnecessary waves such as wraparound waves at a relay station of an FM broadcasting system constituting a single frequency network.

One aspect of the present disclosure is an FM relay device, which includes a receiving unit (3,3A, 3B), a signal reproducing unit (41), a transmitting unit (5), a first profile generation unit (432), and the like. It includes a first suppression unit (433,434), a master station wave extraction unit (441), a second profile generation unit (442), and a second suppression unit (443,444).

The receiving unit is configured to receive the broadcast wave of the FM broadcast via the receiving antennas (2, 2A, 2B). The signal reproduction unit is configured to demodulate the received signal from the receiving unit and remodulate the demodulated signal to generate a transmission signal. The transmission unit is configured to transmit a relay wave that reproduces a broadcast wave using the transmission signal generated by the signal reproduction unit via the transmission antenna (7).

The first profile generation unit calculates the time axis correlation using the transmission signal generated by the signal reproduction unit and the received signal received during the wraparound wave exploration period, and the maximum correlation which is the maximum value of the time axis correlation. It is configured to generate a first delay profile, which is information including the delay time of the transmitted signal relative to the received signal when the value and the maximum correlation value are obtained. The first suppression unit generates a first replica signal by delaying the transmission signal generated by the signal reproduction unit by the delay time according to the first delay profile and adjusting the intensity and phase according to the maximum correlation value. Then, the first replica signal is subtracted from the received signal input to the signal reproduction unit.

The master station wave extraction unit is configured to extract a master station signal, which is a signal component based on the master station wave, from the received signal, using the direct wave from the master station that is the source of the broadcast wave as the master station wave. The second profile generation unit calculates the time axis correlation using the master station signal extracted by the master station wave extraction unit and the received signal received during the multipath wave exploration period, and the maximum value of the time axis correlation. It is configured to generate a second delay profile which is information including the maximum correlation value, and the delay time of the transmission signal with respect to the master station signal when the maximum correlation value is obtained. The second suppression unit delays the master station signal extracted by the master station wave extraction unit by the delay time according to the second delay profile, and adjusts the intensity and phase according to the maximum correlation value to obtain the second replica. It is configured to generate a signal and subtract the second replica signal from the received signal input to the signal reproduction unit.

The wraparound wave exploration period is set in the signal reproduction unit using the wraparound set time (ΔTr) set based on the time required for the relay wave transmitted from the transmitting antenna to be received by the receiving antenna as a wraparound wave. It is set to the period from the generation of the transmission signal to the elapse of the turn-around setting time. During the multipath wave exploration period, the master station signal is transmitted by the master station wave extraction unit using the retransmission delay time (Tr) required for the broadcast wave received by the receiver unit to be transmitted as a relay wave from the transmission unit. It is set to the period from the extraction until the retransmission delay time elapses.

According to the FM relay device configured in this way, the received signal is divided in time, and in the first search period, a wraparound wave having the same waveform as the transmitted signal (that is, the relay wave) is extracted, and the second wave is extracted. In the search period, a multipath wave having the same waveform as the master station signal (that is, a broadcast wave) is extracted. Therefore, both the wraparound wave and the multipath wave can be accurately extracted.

In the FM relay device, since the first replica signal has the same waveform as the wraparound wave, the signal component based on the wraparound wave that causes oscillation can be accurately suppressed.
In the FM relay device, the processing for suppressing the influence of the wraparound wave and the multipath wave is performed at the analog waveform level, so that the information on the delay time and the information on the phase of the wraparound wave and the multipath wave are separated. It can be processed at the same time without being separated into two, and the device configuration can be simplified.

In the FM relay device, by repeating the processing, the wraparound wave and the multipath wave with the highest intensity are processed in order, so that all the wraparound waves and the multipath wave are processed regardless of the number of wraparound waves and the number of multipath waves. Can be dealt with.

It is explanatory drawing which shows the outline of the same frequency FM broadcasting system. It is a block diagram which shows the structure of the FM relay apparatus of 1st Embodiment. It is explanatory drawing which shows the relationship of the master station wave, the relay wave, the wraparound wave, and the multipath wave in the FM relay device. It is explanatory drawing which shows the spectrum of a stereo composite signal. It is a flowchart which shows the processing content in a correlation analysis part. It is explanatory drawing which shows the outline of the delay profile and the parameter used for generating a delay profile. It is explanatory drawing which shows the output level control of the relay wave performed at the time of startup and at the time of oscillation detection. It is a block diagram which shows the structure of the FM relay apparatus of 2nd Embodiment. It is a block diagram which shows the structure of a signal synthesis part. It is a graph which illustrates the detection result of the signal quality. It is explanatory drawing which showed the master station wave component and the wraparound wave component included in the 1st and 2nd received IQ signals, and the synthetic IQ signal by a vector. It is a graph which showed the detection result of the signal quality detected in the processing block B5 on a complex plane. It is explanatory drawing which shows the outline of the delay profile and the parameter used for generating a delay profile. It is explanatory drawing which showed the received IQ signal in the case where there is no interference by a wraparound wave, and the case where there is interference, on a complex plane.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.
[1. First Embodiment]
[1-1. Same frequency FM broadcasting system]
First, the same frequency FM broadcasting system 100 to which the FM relay device 1 according to the present disclosure is applied will be described.

As shown in FIG. 1, the same frequency FM broadcasting system 100 includes a distribution station 101, one or more transmission stations 102, 103, and one or more relay stations 105. The distribution station 101 distributes the same audio signal to the transmission stations 102 and 103 via a predetermined transmission network 104. The transmission stations 102 and 103 are arranged so that at least a part of the respective broadcast areas A1 and A2 overlap each other. In the following, overlapping broadcast areas will be referred to as overlapping area Ad. The transmission stations 102 and 103 transmit FM synchronous broadcasting (hereinafter, simply synchronous broadcasting) by transmitting a broadcast wave in which a carrier wave of the same frequency is frequency-modulated by the same audio signal received from the distribution station 101 via the transmission network 104. )I do. Further, at the transmission stations 102 and 103, the FM modulation characteristics including the timing of FM modulation using the clock synchronized with the 1-second pulse signal (hereinafter, 1 pps) acquired by using GPS are the same between the two transmission stations. Is controlled to be. GPS is an abbreviation for Global Positioning System.

The transmission network 104 used for distributing the audio signal may be different or the same for each transmission station 102, 103. Further, the transmission network 104 is composed of, for example, a wireless transmission network, an IP transmission network, and the like, but is not limited thereto.

The relay station 105 is provided to enable listening to a program in an area (hereinafter referred to as a deafness area) A3 that cannot be covered by the transmission stations 102 and 103 due to the influence of terrain, and is a master station (transmission station 102 in FIG. 1). Relay broadcasting is realized by receiving from and retransmitting at the same frequency.

[1-2. FM relay device configuration]
The FM relay device 1 constituting the relay station 105 will be described.
As shown in FIG. 2, the FM relay device 1 includes a receiving antenna 2, a receiving unit 3, a relay processing unit 4, a transmitting unit 5, a power amplifier 6, and a transmitting antenna 7.

In the following, as shown in FIG. 3, the broadcast wave that directly arrives at the receiving antenna 2 from the transmitting station 102 that is the master station is referred to as the master station wave D, and the reproduced broadcast wave transmitted from the transmitting antenna 7 is referred to as the relay wave Dr. .. Further, the master station wave D transmitted from the master station and reflected by some object and indirectly reaching the receiving antenna 2 is a multipath wave M0 to Mm, and the relay wave Dr wrapping around from the transmitting antenna 7 to the receiving antenna 2 is wrapping around the wave U0. ~ Un. The wraparound waves U0 to Un are numbered in descending order of reception intensity at the receiving antenna 2. Normally, the wraparound wave U0 having the maximum reception intensity is a direct wave that directly reaches the reception antenna 2 from the transmission antenna 7. The other wraparound waves U1 to Un are reflected waves that are reflected by some object and indirectly reach. The wraparound waves U0 to Un all have a waveform in which the relay wave Dr is attenuated and delayed.

Further, the FM relay device 1 is designed so that the relay wave Dr is transmitted from the master station wave D with a delay of the retransmission delay time Tr. The retransmission delay time Tr is one cycle (that is, 52.6 μs) of the pilot signal in order to reduce the distortion of the 19 KHz pilot signal in the stereo composite signal Sc described later due to the interference between the master station wave D and the relay wave Dr. Set to an integral multiple. Specifically, for example, it is set to 6 times the period of the pilot signal, that is, Tr = 315.8 μs. However, under operating conditions where wraparound waves can be sufficiently removed, distortion of the pilot signal due to interference is also reduced, so it is not necessary to limit the frequency to an integral multiple of the pilot signal period.

Returning to FIG. 2, the receiving antenna 2 is arranged so as to receive at least the master station wave D. The receiving antenna 2 may be an omnidirectional antenna or a directional antenna. The master station wave D is an FM modulated wave, and its center frequency is fc.

The receiving unit 3 includes an amplifier 31, a local signal generator 32, a mixer 33, an A / D converter 34, an orthogonal demodulator 35, and a band limiting filter 36.
The amplifier 31 amplifies the received signal from the receiving antenna 2.

The local signal generator 32 generates a local signal LO for down-converting the frequency of the received signal supplied from the receiving antenna 2. In the following, the frequency of the local signal LO is fl.

The mixer 33 down-converts the frequency of the received signal to fc-fl by mixing the received signal amplified by the amplifier 31 with the local signal LO supplied from the local signal generator 32.

The A / D converter 34 samples the received signal down-converted by the mixer 33 at a preset sampling frequency Fad. In the description of processing upstream of the A / D converter 34, "signal" means an analog signal, and in the description of processing downstream of A / D converter 34, "signal" means a series of digital values. do. The sampling frequency Fad of the A / D converter 34 has dozens of bandwidth noise components (or broadcast waves of another channel) other than the desired channel (that is, the frequency band assigned to the broadcast wave D). It is set to about MHz. Specifically, it is set to an integral multiple of the sampling frequency for signal processing, for example, 49.152 MHz. Further, by setting it to an integral multiple of the sampling frequency for signal processing, downsampling described later can be performed simply.

The orthogonal demodulator 35 complexifies the received signal by performing a Hilbert transform on the received signal to obtain an in-phase component and an orthogonal component for each sample value of the received signal. Specifically, by multiplying the received signal by two carrier signals that are orthogonal to each other (that is, the phases are different by 90 °), an I signal representing an in-phase component and a Q signal representing an orthogonal component are generated. The I signal and the Q signal are baseband signals. The number of data may be reduced by downsampling the I signal and the Q signal to a frequency that covers a band that covers twice or more the band of the FM modulated signal, for example, 768 kHz, and the subsequent calculation load in the relay processing unit 4 may be reduced. The sampling frequency Fs for signal processing may be set to a frequency other than 768 kHz as long as it can sufficiently cover the band of the FM modulated signal.

The band limiting filter 36 extracts a signal in the frequency range that the FM-modulated carrier wave can take from the I signal and the Q signal generated by the orthogonal demodulator 35.
Hereinafter, the I signal and the Q signal generated by the receiving unit 3 are collectively referred to as a received IQ signal.

The relay processing unit 4 FM demodulates the received IQ signal generated by the receiving unit 3 and FM-modulates it again to reproduce the I signal and the Q signal having a constant amplitude. The details of the relay processing unit 4 will be described later. Hereinafter, the I signal and the Q signal reproduced by the relay processing unit 4 are collectively referred to as a transmission IQ signal.

The transmission unit 5 includes a quadrature modulator 51, a D / A converter 52, a local signal generator 53, a mixer 54, and an amplifier 55.
The quadrature modulator 51 generates an FM-modulated transmission signal by multiplying the transmission IQ signal reproduced by the relay processing unit 4 by two carrier signals orthogonal to each other and adding them.

The D / A converter 52 converts a transmission signal represented by a series of digital values into an analog signal. In the description of processing downstream of the D / A converter 52, "signal" means an analog signal.

The local signal generator 53 generates a local signal LO for up-converting the frequency of the transmission signal. The local signal generator 53 may be a device common to the local signal generator 32 of the receiving unit 3.

The mixer 54 mixes the transmission signal generated by the D / A converter 52 with the local signal LO generated by the local signal generator 53, and up-converts the frequency of the transmission signal. The center frequency of the up-converted transmission signal is the same as the center frequency fc of the master station wave D.

The amplifier 55 amplifies the transmission signal up-converted by the mixer 54. This amplified transmission signal is called a relay signal.
The power amplifier 6 further amplifies the relay signal generated by the transmission unit 5 and supplies it to the transmission antenna 7. The power amplifier 6 is an amplifier set according to the size of the relay area covered by the relay station 105, and may be connected in multiple stages or may be omitted.

The transmission antenna 7 transmits the relay wave Dr corresponding to the relay signal toward the relay area.
[1-3. Relay processing unit]
The relay processing unit 4 includes a signal reproduction unit 41, an oscillation detection unit 42, a wraparound wave removal unit 43, a multipath wave removal unit 44, and a silence detection unit 45.

The functions of the relay processing unit 4 may be realized entirely by hardware, or at least a part thereof may be realized by processing executed by a microcomputer having a memory which is a non-transitional substantive recording medium. .. In this case, the various functions realized by the microcomputer are realized by the processor executing the program stored in the memory.

[1-3-1. Signal reproduction unit]
The signal reproduction unit 41 includes a band limiting filter 411, an FM demodulation unit 412, a composite filter 413, and an FM modulation unit 414.

The band limiting filter 411 extracts a signal in the frequency range that the FM-modulated carrier wave can take from the received IQ signal supplied from the receiving unit 3 via the wraparound wave removing unit 43 and the multipath wave removing unit 44. The band limiting filter 411 is the same filter as the band limiting filter 36 described above.

The FM demodulation unit 412 calculates the phase of the received signal for each preset unit period Δt using the received IQ signal from which unnecessary components have been removed by the band limiting filter 411, and calculates the phase in the immediately preceding unit period Δt. The instantaneous phase change amount Δθ, which is the difference from the generated phase, is calculated. The unit period Δt is set to the sampling cycle Ts = 1 / Fs, which is the reciprocal of the sampling cycle Fs for signal processing, or an integral multiple thereof. Then, an audio signal is generated by performing Δf detection in which the calculated instantaneous phase change amount Δθ is replaced with the FM modulation degree using a conversion table or conversion formula prepared in advance. The FM modulation degree becomes zero when there is no modulation, and takes a value having a positive or negative sign. The audio signal is a stereo composite signal Sc in the case of stereo broadcasting, and is a monaural audio signal in the case of monaural broadcasting.

As shown in FIG. 4, the stereo composite signal Sc has a pilot signal of 19 kHz, an L + R signal having a frequency component of 15 kHz or less, and an LR signal having a frequency component of ± 15 kHz around 38 kHz. The L + R signal is a signal obtained by adding an L signal and an R signal representing a stereo audio signal. The LR signal is a signal obtained by AM-modulating a carrier wave having a frequency (that is, 38 kHz) twice that of the pilot signal by a signal obtained by subtracting the R signal from the L signal. The monaural audio signal is a signal having a frequency component of 15 kHz or less.

Returning to FIG. 2, in the case of stereo broadcasting, the composite filter 413 removes unnecessary components other than the pilot signal, the L + R signal, and the LR signal from the stereo composite signal Sc demodulated by the FM demodulation unit 412. The composite filter 413 may be configured by three bandpass filters that individually extract each signal, or may be configured by one bandpass filter that collectively extracts each signal. In the case of monaural broadcasting, the composite filter 413 is composed of a bandpass filter that allows a monaural audio signal to pass through. If the composite signal contains a valid signal centered on 57 kHz or 76 kHz, the filter band may be changed as necessary.

The FM modulation unit 414 remodulates the signal demodulated by the FM demodulation unit 412. Specifically, the FM modulation unit 414 calculates the FM modulation degree Δf for each unit period Δt for the audio signal (that is, the stereo composite signal Sc or the monaural audio signal) that has passed through the composite filter 413, and the FM demodulation unit 412 calculates the FM modulation degree Δf. Using the same conversion table used, the instantaneous phase change amount Δθ is calculated from the FM modulation degree Δf. Then, the FM modulation unit 414 generates an I signal representing an in-phase component of the transmission signal and a Q signal representing an orthogonal component, that is, a transmission IQ signal, from this instantaneous phase change component Δθ.

The FM modulation unit 414 is configured to be able to control the output level of the generated transmission IQ signal in a plurality of stages. Then, when the FM relay device 1 is started up or when the oscillation detection signal So output from the oscillation detection unit 42 becomes the active level, the output level of the FM modulation unit 414 is initially set to the minimum level. The active level of the oscillation detection signal So indicates that wraparound oscillation has been detected. After that, the FM modulation unit 414 gradually increases the output level to the maximum level while sequentially removing the wraparound wave U over a preset start-up time. The minimum level is set so that the reception intensity of the wraparound wave UO directly received by the reception antenna 2 is sufficiently smaller than the reception intensity of the master station wave D. The maximum level is set so that signal saturation does not occur due to processing by the transmission unit 5.

[1-3-2. Oscillation detector / silence detector]
The oscillation detection unit 42 monitors the amplitude of the received IQ signal, and outputs the oscillation detection signal So set to the active level when the amplitude fluctuation exceeds a preset threshold value or is saturated. .. That is, in the oscillation detection unit 42, the received IQ signal representing the FM modulated wave has an ideally constant amplitude, but a signal having a different delay (that is, a wraparound wave U0 to Un) is superimposed on the FM modulated wave. If so, oscillation is detected by utilizing the fact that the amplitude fluctuates. It is difficult to correctly demodulate an FM-modulated wave whose amplitude fluctuation range exceeds a certain value. Further, the received IQ signal to be monitored may be a signal on the input side or a signal on the output side of the band limiting filter 411. The silence detection signal Ss is input to the correlation analysis unit 432 of the wraparound wave removing unit 43, the correlation analysis unit 442 of the multipath wave removing unit 44, and the FM modulation unit 414, which will be described later.

The silence detection unit 45 monitors the instantaneous phase change portion Δθ generated by the FM demodulation unit 412, and sets the active level when the state in which the absolute value of the instantaneous phase change portion Δθ is equal to or less than the threshold value continues for a certain period of time or longer. The silent detection signal Ss is output. That is, the silence detection unit 45 detects the silence state by utilizing the fact that the instantaneous phase change amount Δθ other than the pilot signal becomes zero when there is no sound. The threshold value is set to the magnitude of the detection error included in Δθ. The silence detection signal Ss is input to the correlation analysis unit 432 of the wraparound wave removing unit 43, which will be described later.

[1-3-3. Wrap-removing part]
The wraparound wave removing unit 43 includes a band limiting filter 431, a correlation analysis unit 432, an adaptive filter 433, and a subtractor 434.

The band limiting filter 431 extracts a signal in the frequency range that the FM-modulated carrier wave can take from the transmission IQ signal reproduced by the signal reproduction unit 41. The band limiting filter 431 is a filter similar to the band limiting filters 36 and 411 described above.

The correlation analysis unit 432 calculates the time-axis correlation between the received IQ signal output from the wraparound wave removing unit 43 and the transmitted IQ signal supplied from the band limiting filter 431 during the wraparound search period. The wraparound exploration period is a period in which the delay time for the transmitted IQ signal is 0 to ΔTr. ΔTr is a wraparound setting time set to a value larger than the maximum value of the time required for the relay wave Dr transmitted from the transmitting antenna 7 to be received by the receiving antenna 2 as the wraparound wave U. The turn-in set time ΔTr is set by adjusting the number of taps of the adaptive filter 433, and is set to, for example, about 45 μs. However, in FIG. 6, it is described with reference to the reception timing of the master station wave D (that is, the received IQ signal), and the relay wave Dr (that is, the transmission IQ signal) has a retransmission delay time with respect to the master station wave D. Since the delay is only Tr, the wraparound wave search period is represented by Tr to Tr + ΔTr.

Specifically, the correlation analysis unit 432 cuts out the received IQ signal and the transmitted IQ signal for each convolution calculation time To (<ΔTr) set in advance. Then, in the wraparound wave exploration period Tr to Tr + ΔTr, the convolution calculation is performed by multiplying the received IQ signal for the convolution calculation time To and the complex conjugate signal of the transmission IQ signal while sequentially delaying the transmission IQ signal for each time of the sampling period Ts. I do. The convolution calculation time To is set to a time during which the waveform of the signal can be sufficiently identified, for example, about 10 ms for identifying an audio signal having a frequency of 100 Hz to several kHz.

The correlation analysis unit 432 determines the maximum correlation value, which is the maximum value of the correlation coefficient, and the delay time DL (however, DL ≠ 0) from which the maximum correlation value is obtained, based on the time-axis correlation that is the result of the convolution operation. Extract. Then, the correlation analysis unit 432 stores the signal intensity A, the phase θ, and the delay time DL of the delay wave estimated from the extraction result as a delay profile. The delay profile is stored in a rewritable memory. Hereinafter, the delay profile generated by the correlation analysis unit 432 is referred to as a wraparound delay profile.

Here, the flow of processing in the correlation analysis unit 432 will be described with reference to the flowchart shown in FIG.
The processing in the correlation analysis unit 432 is started when the FM relay device 1 is started.

In S110, the correlation analysis unit 432 initializes (for example, zero clear) the stored contents of the wraparound delay profile.
In S120, the correlation analysis unit 432 determines whether or not oscillation is detected by the oscillation detection unit 42, that is, whether or not the oscillation detection signal So has reached the active level. When the correlation analysis unit 432 determines that the oscillation is detected, the process shifts to S130, and when it determines that the oscillation is not detected, the process shifts to S140.

In S130, the correlation analysis unit 432 resets the stored contents of the wraparound delay profile (for example, clears to zero) and returns the processing to S120.
In S140, the correlation analysis unit 432 determines whether or not the silence detection unit 45 has detected the silence state, that is, whether or not the silence detection signal Ss has reached the active level. When it is determined that the silence state is detected, the correlation analysis unit 432 returns the process to S120, and when it is determined that the silence state is not detected, the process shifts to S150.

In S150, the correlation analysis unit 432 calculates the time-axis correlation by executing a convolution operation between the transmitted IQ signal and the received IQ signal. Both the transmitted IQ signal and the received IQ signal are treated as vectors on a complex plane represented by the I signal and the Q signal, and the convolution operation is performed by the complex conjugate signal of the transmitted IQ signal and the complex signal of the received IQ signal. It is done by multiplying with.

In the following S160, the correlation analysis unit 432 creates a delay profile for the wraparound wave based on the time axis correlation which is the calculation result of the convolution operation. In the following, the wraparound delay profile generated for each convolution calculation time To in S160 is referred to as a generation profile, and the already stored wraparound delay profile is referred to as an existing profile.

In the following S170, the correlation analysis unit 432 determines whether or not there is an existing profile whose delay time DL matches the generated profile. If it is determined that the existing matching profile does not exist, the correlation analysis unit 432 shifts the process to S180, and if it determines that the existing matching profile exists, the process shifts to S190.

In S180, the correlation analysis unit 432 additionally stores the generated profile in the memory and returns the processing to S120.
In S190, the correlation analysis unit 432 updates the contents of the existing profile by adding the signal strength A and the phase θ of the generated profile to the signal strength A and the phase θ stored for the matching existing profile, and performs processing. Return to S120.

As a result of the processing by the correlation analysis unit 432, a delay profile is generated for each convolution calculation time To in the wraparound wave exploration period Tr to Tr + ΔTr, and the memory for storing the wraparound wave delay profile is delayed as shown in FIG. Multiple delay profiles for wraparound waves with different time DLs are accumulated. The wraparound delay profile is information representing the states of the wraparound waves U0 to Un received by the receiving antenna 2.

Returning to FIG. 2, the adaptive filter 433 generates a replica IQ signal based on each of the wraparound delay profiles generated by the correlation analysis unit 432 and stored in the memory. The replica IQ signal delays the transmitted IQ signal by the delay time DL based on the delay time DL, the signal strength A, and the phase θ shown in the wraparound delay profile, adjusts the amplitude based on the signal strength A, and performs the phase. This is a signal whose phase is adjusted based on θ. The replica IQ signal is a general term for a replica I signal and a replica Q signal whose phase is 90 ° different from that of the replica I signal. Hereinafter, the replica IQ signal generated by the adaptive filter 433 is referred to as a wraparound replica IQ signal. The adaptive filter 433 generates as many wraparound replica IQ signals as there are wraparound delay profiles.

The subtractor 434 supplies the result of subtracting the wraparound replica IQ signal generated by the adaptive filter 433 from the received IQ signal supplied from the receiving unit 3 to the multipath wave removing unit 44.

[1-3-4. Multipath wave remover]
The multipath wave removing unit 44 includes a master station wave extraction unit 441, a correlation analysis unit 442, an adaptive filter 443, and a subtractor 444.

The master station wave extraction unit 441 extracts the master station wave, which is a direct wave from the master station, from the received IQ signal output by the multipath wave removal unit 44 (that is, input to the signal reproduction unit 41). For the extraction of the master station wave, the characteristic that the amplitude of the FM-modulated wave that is not interfered is constant and the amplitude of the FM-modulated wave that is interfered with is fluctuated is used. That is, it is estimated that the signal having a constant amplitude is a signal based on the master station wave (hereinafter, the master station signal).

The correlation analysis unit 442 calculates the time-axis correlation between the received IQ signal output from the multipath wave removal unit 44 during the multipath search period and the master station signal extracted by the master station wave extraction unit 441. As shown in FIG. 6, the multipath wave exploration period is a period in which the delay time with respect to the master station signal is 0 to Tr.

Specifically, the correlation analysis unit 442 cuts out the received IQ signal and the master station signal for each convolution calculation time To. Then, in the multipath wave exploration period 0 to Tr, the master station signal is sequentially delayed by the time of the sampling period Ts, and the received IQ signal for the convolution calculation time To is multiplied by the complex conjugate signal of the master station signal to convolve. Perform the operation.

The correlation analysis unit 442 creates and stores a delay profile based on the time-axis correlation that is the result of the convolution operation, as in the process of the correlation analysis unit 432. Hereinafter, the delay profile generated by the correlation analysis unit 442 is referred to as a delay profile for multipath waves.

The processing flow in the correlation analysis unit 442 is the same as the processing flow in the correlation analysis unit 432 described using the flowchart shown in FIG. In the description of the process, "wraparound wave" is read as "multipath wave", and "transmission IQ signal" is read as "master station signal".

As a result of the processing by the correlation analysis unit 442, a delay profile for the multipath wave is generated for each convolution calculation time To within the multipath wave exploration period, and the memory for storing the delay profile for the multipath wave is shown in FIG. As described above, a plurality of delay profiles for multipath waves having different delay time DLs are accumulated. The delay profile for multipath waves is information representing the states of the multipath waves M0 to Mm received by the receiving antenna 2.

Returning to FIG. 2, the adaptive filter 443 generates a replica IQ signal based on each of the delay profiles for multipath waves generated by the correlation analysis unit 442 and stored in the memory. The replica IQ signal delays the master station signal by the delay time DL based on the delay time DL, the signal strength A, and the phase θ shown in the delay profile for the multipath wave, and adjusts the amplitude based on the signal strength A. It is a signal whose phase is adjusted based on the phase θ. Hereinafter, the replica IQ signal generated by the adaptive filter 443 is referred to as a replica IQ signal for multipath wave. The adaptive filter 443 generates as many replica IQ signals for multipath waves as there are delay profiles for multipath waves.

The subtractor 444 supplies the signal reproduction unit 41 with the result of subtracting the replica IQ signal for the multipath wave generated by the adaptive filter 443 from the received IQ signal supplied from the wraparound wave removing unit 43.

[1-4. motion]
The operation of the system will be explained.
Immediately after the FM relay device 1 is started, the transmission IQ signal reproduced by the relay processing unit 4 is output at the lowest strength. As a result, the intensity of the wraparound waves U0 to Un received by the receiving antenna 2 is sufficiently reduced, so that oscillation by the wraparound waves U0 to Un is suppressed.

In the wraparound wave removing unit 43, the correlation analysis unit 432 has a delay profile (that is, a delay profile) for the wraparound wave Ui (i = 0, 1, ..., N) having the strongest intensity contained in the received IQ signal at the time of processing. Generate a wraparound delay profile). Therefore, initially, a wraparound delay profile for the direct wave U0 is generated and stored in memory. The adaptive filter 433 generates a wraparound replica IQ signal for the direct wave U0 according to the wraparound delay profile stored in the memory. The subtractor 434 subtracts the wraparound replica IQ signal from the received IQ signal, so that the signal component based on the direct wave U0 is removed from the received IQ signal.

Subsequently, the wraparound wave removing unit 43 performs the same processing on the received IQ signal from which the influence of the direct wave U0 has been removed, so that the wraparound wave U1 has the maximum intensity excluding the direct wave U0. A new delay profile is generated, and the contents of the wraparound delay profile stored in the memory are updated. The adaptive filter 433 generates a wraparound replica IQ signal for the direct wave U0 and the reflected wave U1 according to the wraparound delay profile stored in the memory. The subtractor 434 subtracts the wraparound replica IQ signal from the received IQ signal, so that the signal components based on the direct wave U0 and the reflected wave U1 are removed from the received IQ signal.

Hereinafter, by repeating the same processing, the signal components based on the wraparound waves U0 to Un are sequentially removed from the received IQ signal in descending order of reception intensity. Further, at the time of startup or the like, the output level of the transmitted IQ signal (and thus the relay wave Dr) gradually increases with the progress of the process of removing the wraparound waves U0 to Un described above.

In the multipath wave removing unit 44, the correlation analysis unit 442 performs a delay profile (that is, a delay profile) for the multipath wave Mj (j = 0, 1, ..., M) having the strongest intensity contained in the received IQ signal at the time of processing. , Multipath wave delay profile) is generated and sequentially stored in the memory. That is, initially, a delay profile for the multipath wave for the multipath wave M0 is generated. The adaptive filter 443 generates a multipath wave replica IQ signal for the multipath wave M0 according to the multipath wave delay profile stored in the memory. The subtractor 444 subtracts the replica IQ signal for the multipath wave from the received IQ signal, so that the signal component based on the multipath wave M0 is removed from the received IQ signal.

Subsequently, the multipath wave removing unit 44 performs the same processing on the received IQ signal from which the influence of the multipath wave M0 is removed. That is, a new multipath wave delay profile for the multipath wave M1 having the maximum intensity excluding the multipath wave M0 is newly generated, and the contents of the multipath wave delay profile stored in the memory are updated. The adaptive filter 443 generates a multipath wave replica IQ signal for the multipath waves M0 and M1 according to the multipath wave delay profile stored in the memory. The subtractor 444 subtracts the replica IQ signal for the multipath wave from the received IQ signal, so that the signal component based on the multipath waves M0 and M1 is removed from the received IQ signal.

Hereinafter, by repeating the same processing, the signal components based on the multipath waves M0 to Mm are sequentially removed from the received IQ signal in descending order of reception intensity.
[1-5. Correspondence of terms]
In the present embodiment, the correlation analysis unit 432 corresponds to the first profile generation unit, the adaptive filter 433 and the subtractor 434 correspond to the first suppression unit, and the correlation analysis unit 442 corresponds to the second profile generation unit. The filter 443 and the subtractor 444 correspond to the second suppression unit. The configuration for realizing the function of adjusting the output level in the FM modulation unit 414 corresponds to the output adjustment unit, and the processing in S140 corresponds to the resetting processing. The wraparound delay profile corresponds to the first delay profile, and the wraparound replica signal corresponds to the first replica signal. The multipath wave exploration period corresponds to the multipath wave exploration period, the multipath wave delay profile corresponds to the second delay profile, and the multipath wave replica signal corresponds to the second replica signal.
[1-6. effect]
According to the embodiment described in detail above, the following effects are obtained.

(1a) In the FM relay device 1, the period from the reception of the master station wave D to the elapse of the retransmission delay time Tr is set as the multipath wave search period, and the predetermined time ΔTr elapses after the relay wave Dr is transmitted. The period up to is set as the wraparound wave search period, and the multipath wave M0 to Mm and the wraparound wave U0 to Un are separately extracted. Therefore, both the multipath wave and the wraparound wave can be accurately extracted.

That is, the FM broadcast wave is an analog modulated signal that converts a change in the audio signal into a frequency shift from the central frequency and transmits it, and unlike the terrestrial digital broadcast wave, the information for estimating the wraparound wave U is superimposed. It has not been. In the FM relay device 1, the wraparound wave U and the multipath wave M are searched by dividing the period, so that the wraparound wave U and the wraparound wave M having the same frequency as the master station wave D are searched without superimposing a special signal on the FM broadcast wave. It is possible to estimate the multipath wave M.

(1b) In the FM relay device 1, the wraparound replica IQ signal used for removing the signal component based on the wraparound U0 to Un from the received IQ signal is used as a transmission IQ signal for generating the relay wave Dr, that is, a wraparound. It is generated from the signal that is the source of the waves U0 to Un. Therefore, according to the FM relay device 1, the components based on the wraparound waves U0 to Un that cause oscillation can be accurately suppressed.

(1c) In the FM relay device 1, the master station signal extracted from the received IQ signal, that is, the replica IQ signal for multipath wave used for removing the signal component based on the multipath wave M0 to Mm from the received IQ signal. , Generated from the signal that is the source of the multipath wave M0 to Mm. Therefore, according to the FM relay device 1, the components based on the multipath waves M0 to Mm can be accurately suppressed.

(1d) In the FM relay device 1, the wraparound wave removing unit 43 and the multipath wave removing unit 44 both have one wraparound wave U and a multipath wave M having the highest reception intensity included in the received IQ signal at the time of processing. Generate a delay profile for. Therefore, each time the processing is repeated, the influences of the wraparound wave U and the multipath wave M are suppressed in descending order of signal strength. Therefore, any number of wraparound waves U and multipath waves M can be dealt with as long as the maximum number of replica IQ signals that can be generated by the adaptive filters 433 and 443 is not exceeded.

(1e) In the FM relay device 1, the output level of the relay wave Dr is set to the minimum level at the time of startup and oscillation detection, and with the passage of time (that is, the progress of the process of removing the wraparound waves U0 to Un). , Gradually increase the output level. Therefore, according to the FM relay device 1, as shown in FIG. 7, the final output signal of the relay wave Dr, which is the source of the wraparound waves U0 to Un, is on the receiving antenna 2 at a level higher than that of the master station wave D. Even if it wraps around, the occurrence of wraparound oscillation can be suppressed. The progress of the process of removing the wraparound waves U0 to Un may be determined not only by the passage of time but also by the generation status of the delay profile and the like.

(1f) The FM relay device 1 stops updating the delay profile when a silent state is detected. Therefore, it is possible to suppress a decrease in the accuracy of the delay profile and, by extension, the suppression accuracy of the wraparound wave U and the multipath wave M due to the replica IQ signal due to the influence of the silent state.

(1g) In the FM relay device 1, the replica IQ signal is subtracted from the received IQ signal generated by Hilbert transforming the received signal, that is, the influence of the wraparound wave U and the multipath wave M at the analog waveform level. Performs processing to suppress. Therefore, according to the FM relay device 1, the information regarding the delay time DL of the wraparound wave U and the multipath wave M and the information regarding the intensity A and the phase θ can be simultaneously processed without being separated separately. The configuration can be simplified.

[2. Second Embodiment]
[2-1. Differences from the first embodiment]
Since the basic configuration of the second embodiment is the same as that of the first embodiment, the differences will be described below. It should be noted that the same reference numerals as those in the first embodiment indicate the same configuration, and the preceding description will be referred to.

In the first embodiment described above, the process is executed based on the signal received by one receiving antenna 2. On the other hand, the second embodiment is different from the first embodiment in that the processing is executed based on the signals received by the two receiving antennas 2A and 2B.

[2-2. Constitution]
As shown in FIG. 8, the FM relay device 1A of the second embodiment has two receiving antennas 2A and 2B, two receiving units 3A and 3B, a relay processing unit 4A, a transmitting unit 5, and a power amplifier 6. And a transmission antenna 7.

Ideally, the receiving antennas 2A and 2B are arranged so that the master station wave D is received in the same phase and the wraparound wave U0 is received in the opposite phase (that is, a phase difference of 180 °). Actually, the phase difference between the master station wave D and the wraparound wave U0 received by the receiving antennas 2A and 2B does not have to be exactly opposite in phase, and the wraparound wave U0 is synthesized in the opposite phase and at the same level. At that time, it suffices if the master station wave D is set to remain. That is, in the receiving antennas 2A and 2B, in the signal generated by the signal synthesis unit 40 described later, the master station wave component which is a signal component based on the master station wave D is the signal strength required for processing by the signal reproduction unit 41. Arranged to be included in.

Specifically, the receiving antennas 2A and 2B may be arranged so as to satisfy at least one of the equations (1) and (2). However, the phase difference of the master station wave D received by the receiving antennas 2A and 2B is Δθp, the level difference is ΔPp, the phase difference of the wraparound wave U0 is Δθr, and the level difference is ΔPr. Further, THθ and THP are lower limit threshold values set according to the signal strength required for processing in the signal reproduction unit 41, and are set to, for example, THθ = 10 ° and THP = 3dB.

| Δθp-Δθr | ≧ THθ (1)
ΔPp−ΔPr ≧ THP (2)
The receiving antennas 2A and 2B may be omnidirectional antennas or directional antennas. The master station wave D is an FM modulated wave, and its center frequency is fc.

The receiving unit 3A is connected to the receiving antenna 2A, and the receiving unit 3B is connected to the receiving antenna 2B.
The receiving units 3A and 3B are both configured in the same manner as the receiving unit 3 of the first embodiment. The local signal generator 32 may have a common configuration in the receiving units 3A and 3B.

In the following, the I signal and the Q signal generated by the receiving unit 3A are collectively referred to as the first received IQ signal, and the I signal and the Q signal generated by the receiving unit 3B are collectively referred to as the second reception. It is called an IQ signal.

The relay processing unit 4A FM demodulates the synthesized IQ signal obtained by combining the first received IQ signal and the second received IQ signal generated by the receiving units 3A and 3B, and FM-modulates the signal again to obtain a constant amplitude. I signal and Q signal are reproduced. Hereinafter, the I signal and the Q signal reproduced by the relay processing unit 4A are collectively referred to as a transmission IQ signal.

The transmission unit 5, the power amplifier 6, and the transmission antenna 7 are the same as in the case of the first embodiment.
[2-3. Relay processing unit]
The relay processing unit 4A includes a signal synthesis unit 40, a signal reproduction unit 41, an oscillation detection unit 42, a wraparound wave removal unit 43, a multipath wave removal unit 44, and a silence detection unit 45.

The functions of the relay processing unit 4A may be realized entirely by hardware, like the functions of the relay processing unit 4, or at least a part of the microcomputer has a processor and a memory which is a non-transitional substantive recording medium. It may be realized by the processing executed by.

The configuration of the relay processing unit 4A other than the signal synthesis unit 40 is the same as that of the relay processing unit 4 of the first embodiment.
[2-3-1. Signal synthesizer]
The signal synthesis unit 40 includes an interference wave reverse phase synthesis unit 401, a synthesis error analysis unit 402, a difference detection unit 403, and a coefficient adjustment unit 404.

As shown in FIG. 9, the interference wave reverse phase synthesizing unit 401 includes a signal regulator 81 and an adder 82. The signal regulator 81 adjusts the phase and signal strength of the second received IQ signal according to the combined coefficients (φ, A) set by the coefficient adjusting unit 404. φ is the phase adjustment amount, and A is the level adjustment amount. Here, the maximum wraparound wave U0 included in the first received IQ signal is UA0, and the maximum wraparound wave U0 included in the second received IQ signal is UB0. The coefficient adjusting unit 404 sets the phase adjustment amount φ of the signal regulator 81 so that the phase of the wraparound wave UB0 is opposite to that of the wraparound wave UA0. Further, the level adjustment amount A of the signal regulator 81 is set so that the signal strength of the wraparound wave UB0 matches the signal strength of the wraparound wave UA0. Here, as the level adjustment amount A, a value obtained by dividing the signal strength of the wraparound wave UA0 by the signal strength of the wraparound wave UB0 is expressed in decibels.

The adder 82 is a signal regulator 81, and generates a combined IQ signal by adding the second received IQ signal whose phase and signal strength are adjusted and the first received IQ signal. As a result, the wraparound waves UA0 and UB0 cancel each other out, and a synthetic IQ signal synthesized with the master station waves DA and DB in a state close to the same phase is generated. That is, the wraparound waves UA0 and UB0 correspond to the interference wave components, and the master station waves DA and DB correspond to the broadcast wave components.

The synthesis error analysis unit 402 has a quality detector 930 that detects the signal quality of the synthesis IQ signal. For the signal quality, for example, an error amount can be used. In the case of an FM modulated signal, the error amount can be expressed by a variation in amplitude (for example, a dispersion value) per unit time.

The synthesis error analysis unit 402 further includes five processing blocks B1 to B5. Each processing block Bi (provided that i = 1 to 5) has a signal regulator 91i, an adder 92i, and a quality detector 93i.

The signal regulator 91i is configured in the same manner as the signal regulator 81, the adder 92i is configured in the same manner as the adder 82, and the quality detector 93i is configured in the same manner as the quality detector 930. However, the combined coefficients set in the signal regulators 911 to 915 by the coefficient adjusting unit 404 are different from each other.

Specifically, the synthesis coefficient (φ, AdA) is set in the signal regulator 911 based on the synthesis coefficient (φ, A) set in the signal regulator 81. A composition coefficient (φ, A + dA) is set in the signal regulator 912. A synthesis coefficient (φ−dφ, A) is set in the signal regulator 913. A synthesis coefficient (φ + dφ, A) is set in the signal regulator 914. A synthesis coefficient (φs, A) is set in the signal regulator 915. However, dA represents a minute intensity offset amount, and dφ represents a minute phase offset amount. φs means to scan the phase adjustment amount by 360 °.

Each processing block Bi generates a control composite signal by adding the second received IQ signal whose phase and signal strength are adjusted according to the composite coefficient set in the signal regulator 91i and the first received IQ signal. And detect the signal quality of the generated control composite signal.

That is, the synthesis error analysis unit 402 detects the signal quality of each of the six types of synthesis signals (that is, the synthesis IQ signal and the five types of control synthesis signals) and supplies them to the coefficient adjustment unit 404.

The difference detection unit 403 calculates the average value of the phase difference and the average value of the level difference for each of the first received IQ signal and the second received IQ signal for each preset measurement time, and causes the coefficient adjustment unit 404 to calculate the average value. Supply. For example, 10 ms (reciprocal of 100 Hz) is used as the measurement time, but the measurement time is not limited to this.

Based on the signal quality detection results detected by the quality detector 930 and the processing blocks B1 to B4, the coefficient adjusting unit 404 uses the signal quality as an index to obtain the best signal quality (that is, the minimum error amount). The synthesis coefficient (φ, A) is generated so as to be.

Here, when the combined coefficients are (φ, A−dA), (φ, A), (φ, A + dA), that is, when the phase adjustment amount φ is fixed and the level adjustment amount A is slightly changed. An example of the detection result of the signal quality of FIG. 10 is shown in the upper part of FIG. Further, when the combined coefficient is (φ−dφ, A), (φ, A), (φ + dφ, A), that is, when the level adjustment amount A is fixed and the phase adjustment amount φ is slightly changed. An example of the signal quality detection result is shown in the lower part of FIG. With reference to these two graphs, the signal quality of the combined coefficients (φ, A-dA) and (φ-dφ, A) changed to the minus side with respect to the current combined coefficient (φ, A) is good ( That is, if the error amount is small), the adjustment amounts φ and A are finely adjusted to the minus side. If the signal quality of the combined coefficients (φ, A + dA) and (φ + dφ, A) changed to the positive side with respect to the current combined coefficient (φ, A) is good, the adjustment amounts φ and A are set to the positive side. Make fine adjustments. The fine adjustment amount Δφ of the phase adjustment amount φ and the fine adjustment amount ΔA of the level adjustment amount A may be fixed values, depending on the difference or ratio between the signal quality on the negative side and the signal quality on the positive side. It may be a variable value to be set. Then, the signal qualities at the combined coefficients (φ, Ad1) and (φ, A + dA) are equal, and the signal qualities at the combined coefficients (φ−dφ, A) and (φ + dφ, A) are equal. By repeating the fine adjustment, the synthesis coefficient (φ, A) with the best signal quality can be obtained.

However, the coefficient adjustment unit 404 is a difference detection unit when the reception intensity of the wraparound wave U received by the reception antennas 2A and 2B is higher than the reception intensity of the master station wave D, that is, so-called minus D / U. Using the phase difference φ _AV and the intensity difference A _AV detected in 403, the synthesis coefficients (φ, A) are set so as to satisfy the equations (3) and (4).

φ _AV + φ = 180 ° (3)
A _AV + A = 0dB (4)
The phase difference φ _AV is the result of subtracting the average value of the phase of the second received IQ signal from the average value of the phase of the first received IQ signal. The intensity difference _AAV is the result of dividing the average value of the intensity of the first received IQ signal by the average value of the intensity of the second received IQ signal, and the unit is decibel.

That is, in the case of minus D / U, the difference detection unit 403 detects the phase difference φ _AV and the intensity difference A _AV for the wraparound wave U0 having the highest level, and therefore, this value is used as the synthesis coefficient (φ, A). ) May be used.

The master station wave component DA included in the first received IQ signal and the master station wave component DB included in the second received IQ signal, which are input to the signal synthesis unit 40 due to the arrangement of the receiving antennas 2A and 2B, are shown in FIG. As shown in 11, the phases are substantially in phase. Further, it is desirable that the wraparound wave component UA included in the first received IQ signal and the wraparound wave component UB included in the second received IQ signal have a phase difference close to 180 °, but the position of the master station wave component. It should be different from the phase difference. In the signal synthesis unit 40, the second received IQ signal whose wraparound component UA and UB are adjusted by the synthesis coefficient (φ, A) so as to have the opposite phase and the same signal strength, and the first received IQ signal Additive synthesis is performed. As a result, the combined wraparound wave components UA and UB cancel each other out, and the master station wave components UA and UB are synthesized in a state where the phase difference from the original is added by the phase adjustment amount φ. To.

The coefficient adjusting unit 404 performs phase synthesis as shown in FIG. 12 based on the detection result in the processing block B5, that is, the detection result of the signal quality of the control composite signal synthesized by the synthesis coefficient (φs, A). Generate a pattern graph. The phase synthesis pattern graph shows the signal strength of the wraparound wave U0 detected in each phase when the phase of the master station wave D is set to 0 ° and the phase adjustment amount applied at the time of synthesis is changed by 0 to 360 °. be. The phase corresponding to the recess in the phase synthesis pattern graph represents the phase difference of the wraparound wave U0 with respect to the master station wave D. That is, the coefficient adjusting unit 404 removes the wraparound wave U0 by forming an antenna synthesis null in the arrival direction of the signal having this phase difference (that is, the wraparound wave U0). Therefore, the initial value of the composition coefficient may be set by using the phase difference read from the phase composition pattern fluff.

[2-4. motion]
The operation of the system will be explained.
Immediately after the FM relay device 1A is started, the transmission IQ signal reproduced by the relay processing unit 4 is output at the lowest intensity. As a result, the intensity of the wraparound waves U0 to Un received by the receiving antennas 2A and 2B is sufficiently reduced, so that the oscillation due to the wraparound waves U0 to Un is suppressed.

The signal synthesizer 40 has a phase difference and a level between the first received IQ signal and the second received IQ signal so that the wraparound waves U0 received by the receiving antennas 2A and 2B have opposite phases and the signal intensities are equal. Adjust the difference and synthesize. Therefore, as shown in FIG. 13, the maximum wraparound wave U0 is suppressed in the synthetic IQ signal.

The wraparound wave removing unit 43 removes the wraparound waves U1 to Un that cannot be removed by the signal synthesizing unit 40 by using the delay profile in descending order of reception intensity. If the signal synthesis unit 40 does not sufficiently suppress the wraparound wave U0, a delay profile is generated when the strength of the suppressed wraparound wave U0 becomes the maximum intensity in the synthesized IQ signal. To. Therefore, the wraparound wave U0 that remains unremoved by the signal synthesis unit 40 is also removed from the synthetic IQ signal.

The multipath wave removing unit 44 removes the multipath waves M0 to Mm by using the delay profile in descending order of reception intensity.
Further, at the time of startup or the like, the output level of the transmitted IQ signal (and thus the relay wave Dr) gradually increases with the progress of the process of removing the wraparound waves U0 to Un described above.

[2-5. Correspondence of terms]
In the present embodiment, the synthesis error analysis unit 402 and the coefficient adjustment unit 404 correspond to the coefficient setting unit.

[2-6. effect]
According to the second embodiment described in detail above, the effects (1a) to (1 g) of the above-mentioned first embodiment are exhibited, and the following effects are further achieved.

(2a) In the FM relay device 1A, the interference wave of the maximum intensity (for example, the wraparound wave U0) is removed by synthesizing the signals obtained from the two receiving antennas 2A and 2B, so that the entire level of the wraparound wave U can be quickly reduced. Can be reduced. As a result, oscillation due to the wraparound wave U is suppressed, and the stability of operation can be improved.

(2b) In the FM relay device 1A, the signal synthesis unit 40 removes the interference wave by synthesizing the signals obtained from the two receiving antennas 2A and 2B, so that the maximum intensity interference wave becomes the relay wave Dr. Can effectively remove this interference wave even if it has a different waveform. For example, even when dissimilar program broadcasts interfere with each other on the same channel, the phase difference of the dissimilar program broadcasts is controlled to be opposite in phase by synthesizing the antennas, and the interference can be eliminated. In this case, the maximum intensity wraparound wave U0 is removed by processing using the delay profile.

(2c) In the FM relay device 1A, in order to remove the wraparound wave U using the delay profile for the synthetic IQ signal in which the interference wave of the maximum intensity is suppressed, the range of the signal strength handled by the wraparound wave removing unit 43 is set. It can be narrowed, and the configuration of the wraparound wave removing unit 43 can be simplified.

[3. Other embodiments]
Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and can be variously modified and implemented.

(3a) In the present disclosure, the delay profile stored in the memory is initialized (that is, S110) when the FM relay devices 1 and 1A are started, and is reset (that is, S140) when oscillation is detected. The stored contents are configured to be cleared to zero at the time of initialization and resetting, but the present disclosure is not limited to this. For example, the update history of the delay profile is stored in the memory, and the correlation analysis unit 432,442 stores the delay profile based on the update history instead of clearing the stored contents of the memory in which the delay profile is stored to zero at the time of oscillation detection. The contents of may be returned to the state before oscillation detection. According to such a configuration, after the oscillation is detected, it is possible to quickly return to the state where the influence of the wraparound waves U0 to Un is sufficiently suppressed.

(3b) In the present disclosure, the FM modulation unit 414 controls the output level of the relay wave Dr at the time of activation and at the time of oscillation detection, but it is performed by changing the amplification factor of the amplifier 55 and the power amplifier 6. It may be done by the attenuator provided separately.

(3c) In the present disclosure, the case where the FM relay device 1, 1A is expanded in the FM synchronous broadcasting system using SFN is exemplified, but the present invention is not limited to this, and is not limited to FM synchronous broadcasting. It may be applied when the broadcasting area is expanded in the FM broadcasting system.

(3d) The FM relay devices 1 and 1A are used for the state of the received IQ signal (in the case of the FM relay device 1A, at least one of the first received IQ signal, the second received IQ signal, and the synthesized IQ signal) and the synthesis. A configuration for displaying the signal quality detection result (only in the case of the FM relay device 1A) by the error analysis unit 402 may be provided. Specifically, the FM relay devices 1 and 1A generate an image signal representing an image in which the received IQ signal is plotted on a complex plane and an image in which the signal quality is graphed (only in the case of the FM relay device 1A). It may be provided with a generation unit and an image output terminal for outputting an image signal. Further, a display device connected to the image output terminal, a wireless communication device for transmitting an image signal to an external display device (for example, a mobile phone or the like), or the like may be provided.

As shown in FIG. 14, the image obtained by plotting the received IQ signal on the complex plane can obtain different images depending on whether there is interference due to wraparound wave, multipath wave, or heterogeneous program interference wave and when there is interference. Therefore, the presence or absence of interference can be visually confirmed. An image in which the signal quality is graphed (see, for example, FIGS. 10 and 12) can be displayed by fixing the synthesis coefficient to (φ = 180 °, A = 1), for example, so that the receiving antennas 2A and 2B can be displayed. You can proceed with the work while checking the condition at the time of installation.

(3e) In the FM relay devices 1 and 1A, the center frequency of the carrier wave is set to be the same for the received IQ signal used for the master station wave D and the relay wave Dr (and by extension, the transmitted IQ signal). Is not limited to this. For example, the center frequency of the carrier wave of the relay wave Dr may be different from the center frequency of the carrier wave of the master station wave D by the offset frequency Δfo. In this case, the offset frequency Δfo is set within the range of the center frequency deviation (20 ppm) allowed in the FM broadcast wave, and may be set to, for example, about 100 Hz (1.25 ppm if the frequency of the carrier signal is 80 MHz). ..

Further, in this case, when calculating the time axis correlation between the received IQ signal or the synthesized IQ signal and the transmitted IQ signal, the length of the section for performing the convolution calculation is set to the offset time To, which is the reciprocal of the offset frequency Δfo. You may. As a result, the signal component based on the master station wave D included in the received IQ signal or the synthesized IQ signal has a weak correlation with the transmitted IQ signal, and is detected as a kind of noise in the calculation by the correlation analysis unit 432. Therefore, it is possible to suppress that the signal component based on the master station wave D interferes with the detection of the wraparound wave U. That is, by making the center frequency of the carrier wave different between the relay wave Dr and the master station wave D by the offset frequency Δfo, it may be possible to estimate the wraparound wave without superimposing a special signal on the FM broadcast wave.

(3f) A plurality of functions possessed by one component in the above embodiment may be realized by a plurality of components, or one function possessed by one component may be realized by a plurality of components. .. Further, a plurality of functions possessed by the plurality of components may be realized by one component, or one function realized by the plurality of components may be realized by one component. Further, a part of the configuration of the above embodiment may be omitted. Further, at least a part of the configuration of the above embodiment may be added or replaced with the configuration of the other above embodiment.

(3g) In addition to the FM relay devices 1, 1A described above, a program for operating a computer as the FM relay devices 1, 1A, a non-transitional actual recording medium such as a semiconductor memory in which this program is recorded, and a delay profile generation. The present disclosure can also be realized in various forms such as methods.

1,1A ... FM relay device, 2,2A, 2B ... receiving antenna, 3,3A, 3B ... receiving unit, 4,4A ... relay processing unit, 5 ... transmitting unit, 6 ... power amplifier, 7 ... transmitting antenna, 40 ... signal synthesis unit, 41 ... signal reproduction unit, 42 ... oscillation detection unit, 43 ... wraparound wave removal unit, 44 ... multipath wave removal unit, 45 ... silence detection unit, 401 ... interference wave reverse phase synthesis unit, 402 ... synthesis Error analysis unit, 403 ... Difference detection unit, 404 ... Coefficient adjustment unit, 431 ... Band limiting filter, 432,442 ... Correlation analysis unit, 433,443 ... Adaptive filter, 434,444 ... Subtractor, 441 ... Master station wave extraction Department.

Claims (12)

A receiving unit (3,3A, 3B) configured to receive the broadcast wave of FM broadcasting via a receiving antenna (2,2A, 2B), and
A signal reproduction unit (41) configured to generate a transmission signal by demodulating the received signal from the reception unit and remodulating the demodulated signal.
A transmission unit (5) configured to transmit a relay wave that reproduces the broadcast wave using the transmission signal generated by the signal reproduction unit via the transmission antenna (7).
The time axis correlation is calculated using the transmitted signal generated by the signal reproduction unit and the received signal received during the wraparound wave exploration period, and the maximum correlation value which is the maximum value of the time axis correlation and the maximum correlation value and the maximum correlation value which is the maximum value of the time axis correlation are calculated. A first profile generation unit (432) configured to generate a first delay profile which is information including a delay time of the transmission signal with respect to the reception signal when the maximum correlation value is obtained.
The first replica signal is generated by delaying the transmission signal generated by the signal reproduction unit by the delay time according to the first delay profile and adjusting the intensity and phase according to the maximum correlation value. A first suppression unit (433,434) configured to subtract the first replica signal from the received signal input to the signal reproduction unit.
A master station wave extraction unit configured to extract a master station signal which is a signal component based on the master station wave from the received signal, using the direct wave from the master station which is the source of the broadcast wave as the master station wave. (441) and
The time axis correlation is calculated using the master station signal extracted by the master station wave extraction unit and the received signal received during the multipath wave exploration period, and is the maximum value of the time axis correlation. A second profile generation unit (442) configured to generate a second delay profile which is information including a correlation value and a delay time of the transmission signal with respect to the master station signal when the maximum correlation value is obtained. When,
The second replica signal is obtained by delaying the master station signal extracted by the master station wave extraction unit by the delay time according to the second delay profile and adjusting the intensity and phase according to the maximum correlation value. A second suppression unit (443,444) configured to subtract the second replica signal from the received signal input to the signal reproduction unit.
Equipped with
The wraparound wave exploration period uses a wraparound set time (ΔTr) set based on the time required for the relay wave transmitted from the transmitting antenna to be received by the receiving antenna as a wraparound wave. It is set in the period from the generation of the transmission signal by the signal reproduction unit to the elapse of the turn-around set time.
In the multipath wave exploration period, the master station wave extraction unit uses the retransmission delay time (Tr) required for the broadcast wave received by the reception unit to be transmitted from the transmission unit as the relay wave. Was set to the period from the extraction of the master station signal to the elapse of the retransmission delay time.
FM relay device. The FM relay device according to claim 1.
When the FM relay device is started, the output level of the relay wave transmitted by the transmission antenna is set to a preset minimum level, and the output level of the relay wave is set to a preset maximum level to remove wraparound waves. Output adjustment unit (414) configured to adjust in stages according to progress.
FM relay device further equipped with. The FM relay device according to claim 2.
An oscillation detection unit (42) configured to detect the oscillation of the FM relay device, and
Further prepare
The first profile generation unit is configured to store the generated first delay profile, and the second profile generation unit is configured to store the generated second delay profile.
The first suppression unit generates the first replica signal according to the first delay profile stored in the first profile generation unit, and the second suppression unit is stored in the second profile generation unit. It is configured to generate the second replica signal according to the second delay profile.
The first profile generation unit and the second profile generation unit are configured to perform reset processing for resetting the stored contents of the first delay profile and the second delay profile when oscillation is detected by the oscillation detection unit. Was done,
The output adjusting unit is configured to adjust the output level of the relay wave not only at the time of activation but also at the time of oscillation detection by the oscillation detecting unit.
FM relay device. The FM relay device according to claim 3.
As the resetting process, the first profile generation unit erases the stored contents of the first delay profile, and the second profile generation unit erases the stored contents of the second delay profile. Device. The FM relay device according to claim 3.
The first profile generation unit is configured to further store the history of the first delay profile, and the second profile generation unit is configured to further store the history of the second delay profile.
As the resetting process, the first profile generation unit returns the stored contents of the first delay profile to the state before oscillation detection using the history of the first delay profile, and the second profile generation unit receives the second profile generation unit. As the resetting process, the stored contents of the second delay profile are configured to return to the state before oscillation detection by using the history of the second delay profile.
FM relay device. The FM relay device according to any one of claims 1 to 5.
Further, a silence detection unit (45) for detecting the silence state of the broadcast wave is further provided.
The first profile generation unit and the second profile generation unit are configured to stop the generation of the first delay profile and the second delay profile while the silence detection unit detects the silence state. FM relay device. The FM relay device according to any one of claims 1 to 6.
The receiving unit converts the received signal into an I signal representing an in-phase component and a Q signal representing an orthogonal component and outputs the signal.
The transmission unit is an FM relay device configured to orthogonally demodulate and transmit the transmission signal represented by the I signal and the Q signal. The FM relay device according to any one of claims 1 to 7.
The receiving unit is configured to receive the broadcast wave using two receiving antennas (2A, 2B).
The two received signals obtained from the receiving unit are configured to be combined so that the phases of the interference wave components, which are signal components based on the interference waves, are out of phase and the signal intensities of the interference wave components match. Further equipped with a signal synthesizer (40)
The signal reproduction unit, the first profile generation unit, the first suppression unit, the master station wave extraction unit, the second profile generation unit, and the second suppression unit are the signals as the reception signal to be processed. It is configured to use the synthesized signal synthesized in the synthesis part.
FM relay device including. The FM relay device according to claim 8.
The two receiving antennas are FM relay devices arranged so that a broadcast wave component, which is a signal component based on the broadcast wave, is included in the combined signal at a signal strength required for processing in the signal reproduction unit. The FM relay device according to claim 9.
The phase difference of the broadcast wave received by the two receiving antennas is Δθp, the level difference of the broadcast wave is ΔPp, the phase difference of the interference wave is Δθr, the level difference of the interference wave is ΔPr, and the signal reproduction unit The lower limit thresholds set according to the signal strength required for the processing of are set to THθ and THp.
The two receiving antennas are FM relay devices arranged so as to satisfy at least one of | Δθp-Δθr | ≧ THθ and ΔPp-ΔPr ≧ THP. The FM relay device according to any one of claims 8 to 10.
The signal synthesis unit is
Interference wave reverse phase synthesis configured to generate the composite signal by synthesizing the two received signals obtained from the receiver in a state where the phase difference and the level difference are adjusted according to the set synthesis coefficient. Part (401) and
A coefficient setting unit (402, 404) configured to set the composite coefficient using the signal quality of the composite signal as an index, and
FM relay device including. The FM relay device according to claim 11.
The signal synthesis unit further includes a difference detection unit (403) configured to calculate the average value of the phase difference and the average value of the level difference of the two received signals for each preset measurement time.
The coefficient setting unit is an FM relay device configured to set the synthesis coefficient according to the detection result of the difference detection unit when the interference wave has a higher reception intensity than the broadcast wave.

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