JPH10303852A - Reference carrier frequency recovery method for orthogonal frequency division multiplex modulation - Google Patents

Abstract

(57) Abstract: A reference carrier frequency required for orthogonally synchronous detection of an OFDM transmission signal is stably and accurately reproduced. SOLUTION: An OFDM transmission signal in which a non-modulated carrier signal (reference signal) is interposed at a fixed period and transmitted from a transmitter is received, and a reference signal included in the OFDM transmission signal is detected by an fc detection circuit 5. Extract. A signal generation circuit 6 that repeats a continuous signal obtained by repeating the extracted reference signal.
Generated by On the basis of the continuous signal, the voltage controlled oscillator loop including the frequency control circuit 8 and the VCO circuit 9 generates a 0-degree signal and a 90-degree signal, and based on the 0-degree signal and the 90-degree signal, The IF signal is subjected to quadrature synchronous detection to obtain a baseband I signal and a baseband Q signal.
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Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an OFD suitable for a digital television broadcast, a digital audio broadcast or a digital television material transmission apparatus.
The present invention relates to an M modulation method, and more particularly to a reference carrier frequency reproduction method of orthogonal frequency division multiplex modulation for reproducing a reference carrier frequency at a receiver side using an unmodulated carrier signal transmitted intermittently.

SUMMARY OF THE INVENTION The present invention relates to OFDM (Orthogonal Frequency Division Multiplexing).
plexing) relates to a reference carrier frequency reproduction method of a modulation method, in which a transmitter side intermittently transmits an unmodulated carrier signal of a reference carrier frequency, and a receiver side repeats the unmodulated carrier signal to form a continuous signal. Is generated, and the voltage-controlled oscillator is operated by using the continuous signal to reproduce a carrier having an accurate and stable reference carrier frequency.

[0003]

2. Description of the Related Art Conventionally, as a method of reproducing a reference carrier frequency for demodulating an OFDM modulated signal, a method of reproducing a reference carrier frequency by locking a frequency based on a reproduced frame synchronization signal, and a method of receiving a signal. A method is known in which a frequency deviation is corrected by detecting a phase error of the obtained data to reproduce a reference carrier frequency.

In signal transmission using such an OFDM modulation method, it is required that a receiving side reproduce an accurate reference carrier frequency.

[0005]

However, in the conventional reproducing method of the reference carrier frequency, when the difference between the transmitted reference frequency and the oscillator of the reference frequency of the receiver is large,
In any case, there is a problem that it is difficult to accurately reproduce the reference carrier frequency.

In view of the above circumstances, the present invention is directed to claim 1, wherein a signal of a reference carrier frequency which is a center frequency of an OFDM transmission frequency band is inserted at a predetermined position in a synchronization signal section of an OFDM signal on a transmission side. Transmit intermittently and on the receiving side,
By taking out this signal and using the signal created by repeating this signal, the reference carrier frequency is stabilized by forming a voltage-controlled oscillator loop that locks the frequency.
An object of the present invention is to provide a reference carrier frequency reproduction method of orthogonal frequency division multiplex modulation that can reproduce accurately.

Further, in the second aspect, the ratio between the length of the frequency locking signal intermittently transmitted and the time until the next signal is transmitted is made an integer, thereby extracting the ratio on the receiving side. Provided is a reference carrier frequency reproduction method of orthogonal frequency division multiplex modulation, which can make a continuous signal without a break in time when repeating a reference signal, and can create a more stable continuous signal for frequency locking. It is intended to be.

According to a third aspect of the present invention, the reference signal extracted on the receiving side is stored as digital data, and this data is repeated and read out, so that it is simpler and more stable than a continuous signal repeated as an analog signal. It is an object of the present invention to provide a reference carrier frequency reproduction method of orthogonal frequency division multiplex modulation capable of producing a continuous signal for frequency locking.

According to a fourth aspect of the present invention, a continuous signal for frequency lock is created by using a part of a signal for frequency lock which is intermittently transmitted, so that the reception side transmits the reference signal. An object of the present invention is to provide a reference carrier frequency reproduction method of orthogonal frequency division multiplex modulation that can generate a continuous signal for frequency lock even when the position and length cannot be obtained accurately.

According to a fifth aspect of the present invention, when a part of the intermittently transmitted frequency lock signal is extracted on the receiving side, the ratio between the cutout length and the time until the next frequency lock signal is extracted is determined. By using an integer, when repeating the reference signal extracted on the receiving side, it is possible to make a continuous signal without a break in time as in claim 2, thereby creating a more stable continuous signal for frequency locking. It is an object of the present invention to provide a reference carrier frequency reproduction method of orthogonal frequency division multiplex modulation that can perform the above.

According to a sixth aspect of the present invention, a continuous signal is generated by repeating a signal obtained by aligning and adding the phase of a reference signal extracted on the receiving side, thereby obtaining a C / N (signal pair) of a continuous signal used for frequency locking. Noise ratio)
It is an object of the present invention to provide an orthogonal frequency division multiplex modulation reference carrier frequency reproduction method capable of reproducing a stable and accurate reference frequency even when noise characteristics on a transmission path are poor.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above object, according to the first aspect of the present invention, there is provided an OFDM (Orthogonal Frequency Division Multiplexing) modulation type OFDM transmission signal at a predetermined position in a synchronization signal section. Receiving means for intermittently transmitting an OFDM transmission signal by inserting a reference signal having a reference carrier frequency which is the center frequency of the OFDM transmission frequency band, and extracting the reference signal from the received OFDM transmission signal Reference signal extracting means, and a continuous signal generating means for holding the extracted reference signal, repeating the held reference signal until the next reference signal is extracted, and generating a continuous signal, A voltage-controlled oscillator loop that locks the frequency by using this continuous signal is formed, and O
Reference frequency reproducing means for reproducing a reference carrier frequency for obtaining a baseband I signal and a baseband Q signal of an FDM signal is provided.

According to a second aspect of the present invention, in the reference carrier frequency recovery system of the orthogonal frequency division multiplex modulation according to the first aspect, a time interval between the reference signals inserted into the OFDM transmission signal and transmitted intermittently. The time interval between each reference signal and the time width of each reference signal are determined so that a value obtained by dividing the interval by the time width of each reference signal becomes an integer.

According to a third aspect of the present invention, in the reference carrier frequency reproduction system of the orthogonal frequency division multiplex modulation according to the first aspect, the continuous signal generation means samples digital data obtained by sampling the extracted reference signal. And repeatedly reading the held digital data to generate a pseudo continuous signal.

According to a fourth aspect of the present invention, in the reference carrier frequency recovery system of the orthogonal frequency division multiplex modulation according to the first aspect, the continuous signal extracting means is inserted into an OFDM transmission signal and transmitted intermittently. It is a means for extracting a part of the reference signal.

According to a fifth aspect of the present invention, in the reference carrier frequency reproduction system of the orthogonal frequency division multiplex modulation according to the fourth aspect, a part of the reference signal inserted into the OFDM transmission signal and transmitted intermittently is transmitted. At the time of extraction on the receiving side, the time width of the reference signal is determined so that a value obtained by dividing a time interval until the next reference signal is extracted by the extraction time length is an integer. I have.

According to a sixth aspect of the present invention, a reference signal having a reference carrier frequency which is the center frequency of an OFDM transmission frequency band is provided at a predetermined position in a synchronization signal section constituting an OFDM transmission signal of an OFDM (orthogonal frequency division multiplexing) modulation method. Receiving means for receiving an intermittently transmitted OFDM transmission signal by inserting a signal, reference signal extracting means for extracting the reference signal from the received OFDM transmission signal, and holding each of the extracted reference signals A phase adjusting means for generating a phase-adjusted reference signal by aligning and adding the phases of the held reference signals, and repeating the phase-adjusted reference signal output from the phase adjusting means. , A continuous signal generating means for generating a continuous signal, and a voltage-controlled oscillator loop for locking the frequency using the continuous signal.
Reference frequency reproducing means for reproducing a reference carrier frequency for obtaining a baseband I signal and a baseband Q signal of an FDM signal is provided.

A feature is that the length of a part of the reference signal is determined so that a value obtained by dividing the length of time until the extraction becomes an integer.

In the above structure, according to the first aspect, the OF
The OFDM is placed at a predetermined position in the synchronization signal section of the DM transmission signal.
A reference signal having a reference carrier frequency, which is the center frequency of the transmission frequency band, is inserted and transmitted.On the receiving side, the reference signal is extracted, and a frequency is locked by using a continuous signal obtained by repeating the reference signal. By constructing a voltage controlled oscillator loop to reproduce the reference carrier frequency, the reference carrier frequency is reproduced stably and accurately.

According to a second aspect of the present invention, a value obtained by dividing the time interval between the reference signals inserted intermittently in the OFDM transmission signal and intermittently by the time width of each reference signal into an integer. By determining the time interval between each reference signal and the time width of each reference signal, a break in the signal obtained by repeating the reference signal is eliminated, and the reference carrier frequency is reproduced stably and accurately. .

According to a third aspect of the present invention, a reference signal inserted into an OFDM transmission signal and intermittently transmitted is extracted on the receiving side, and digital data obtained by sampling the reference signal is stored. Thereafter, the digital data is repeated and read out to create a pseudo continuous signal. Using this continuous signal, a voltage-controlled oscillator loop for locking the frequency is formed, and the reference carrier frequency is reproduced, whereby the reference signal is reproduced. Is repeated, and the reference carrier frequency is reproduced stably and accurately.

According to a fourth aspect of the present invention, a part of the reference signal inserted intermittently in the OFDM transmission signal and intermittently transmitted is extracted on the receiving side, and digital data obtained by sampling the reference signal is obtained. By storing and subsequently reading this digital data repeatedly to create a pseudo continuous signal, utilizing this continuous signal, forming a voltage controlled oscillator loop to lock the frequency, and reproducing the reference carrier frequency, Even when the position and length of the reference signal cannot be obtained accurately, the reference carrier frequency is reproduced stably and accurately.

According to a fifth aspect of the present invention, when a part of a reference signal which is inserted into an OFDM transmission signal and is intermittently transmitted is extracted on the receiving side, the next reference signal is extracted with this extraction time length. The time width of the reference signal is determined so that the value obtained by dividing the time interval until becomes an integer, thereby eliminating a break in the signal obtained by repeating the reference signal, stabilizing the reference carrier frequency, and accurately. Reproduce.

According to a sixth aspect of the present invention, a reference signal inserted into an OFDM transmission signal and intermittently transmitted is extracted on the receiving side, and a signal obtained by adjusting the phases of these reference signals and adding them is repeated. A continuous signal is created by using the continuous signal, and a voltage controlled oscillator loop for locking the frequency is formed by using the continuous signal. By reproducing the reference carrier frequency, the C / N (signal-to-noise ratio) of the reference signal is reduced. Even in a bad case, a signal obtained by repeating the reference signal is stabilized, and the reference carrier frequency is reproduced stably and accurately.

[0025]

FIG. 1 is a block diagram showing an example of a transmission / reception system to which a reference carrier frequency reproduction method of orthogonal frequency division multiplex modulation according to the present invention is applied.

The transmission / reception system 1 shown in FIG. 1 modulates transmission data to be transmitted by an OFDM modulation method to generate an OFDM transmission signal having a signal format shown in FIG. Transmitter 2 and this transmitter 2
And a receiver 3 for receiving the OFDM transmission signal transmitted from the receiver 3 and reproducing the transmission data. The transmitter 2 transmits the OFDM transmission signal in which a non-modulated carrier signal (reference signal) is inserted at a constant period. A signal is generated and transmitted, and the receiver 3 receives the OFDM transmission signal and extracts a reference signal included in the OFDM transmission signal. Then, the receiver 3 reproduces the 0-degree signal and the 90-degree signal based on the extracted reference signal,
Based on the 0-degree signal and the 90-degree signal, the IF signal obtained from the OFDM transmission signal is subjected to quadrature synchronous detection to reproduce a baseband I signal and a baseband Q signal.

In this case, the OFDM transmission signal is as shown in FIG.
As shown in (a), each of a plurality of OFDM signals including transmission data to be transmitted and one or more unmodulated carrier signals (centered) inserted in a synchronization signal section inserted between the OFDM signals. A reference signal indicating a reference carrier frequency of the frequency fc), and a value obtained by dividing the time interval between each reference signal included in the OFDM transmission signal by the time width of each reference signal is an integer. Thus, the ratio between the time interval between the reference signals and the time width of each reference signal is determined.

The receiver 3 performs narrow-band band-pass filtering on the IF signal obtained by receiving the OFDM transmission signal by the receiving means (not shown), as shown in FIG. OFDM including a reference signal
A BPF circuit 4 for extracting a signal and an IF signal after band-pass filtering output from the BPF circuit are taken in, and a signal component of a frequency fc (a reference signal indicating a reference carrier frequency fc) included in the IF signal is taken. Fc detection circuit 5 for extracting a part or all of the fc detection circuit 5
Each time a reference signal is output intermittently, the signal is fetched and sampled, the digital data obtained by this sampling processing is stored, and the time until the next reference signal is output from the fc detection circuit 5 is output. , Holding the digital data and repeating the same to generate a continuous signal having a frequency fc as shown in FIG. 2B, and a continuous signal output from the repeated signal generating circuit 6. And a BPF circuit 7 that performs band-pass filtering to cut off unnecessary frequency components other than the signal whose center frequency is fc.

Further, the receiver 3 has a frequency lock loop (for example, Costas loop), and the BPF circuit 7
Is compared with the frequency / phase of the input feedback signal, and based on the comparison result, the frequency / phase of the feedback signal is compared with the frequency / phase of the continuous signal. A frequency control circuit 8 for generating a control voltage signal required for matching, and oscillating at a frequency / phase corresponding to the value of the control voltage signal output from the frequency control circuit 8 to generate an OF signal included in the IF signal
A 0-degree signal having a frequency fc required for quadrature demodulating the DM signal is generated, and this signal is used as a feedback signal.
A π / 2 phase shifter 10 that takes in the 0-degree signal output from the VCO circuit 9 and shifts the phase by π / 2 to generate a 90-degree signal;
Based on the 0-degree signal output from the circuit 9, the BPF circuit 4
Synchronously detects the in-phase component in the IF signal output from
Multiplexer circuit 11 for demodulating baseband I signal
And a multiplexer circuit 12 that synchronously detects an orthogonal component in the IF signal output from the BPF circuit 4 based on the 90-degree signal output from the π / 2 phase shift circuit 10 and demodulates a baseband Q signal. Have.

The OFDM transmitted from the transmitter 2
The transmission signal is received, a reference signal included in the IF signal of the OFDM transmission signal is extracted, and the reference signal is repeated to generate a continuous signal. Further, based on the continuous signal, the oscillation frequency of the VCO circuit 9 is determined. / Phase is controlled to generate a 0-degree signal and a 90-degree signal having a frequency / phase that matches the frequency fc of the reference signal, and are included in the IF signal based on the 0-degree signal and the 90-degree signal. The in-phase component and the quadrature component are subjected to quadrature synchronous detection to demodulate a baseband I signal and a baseband Q signal, and then a baseband I signal is omitted by a DFT circuit (not shown).
A signal and a baseband Q signal are subjected to a discrete Fourier transform to reproduce transmission data.

Thus, the O transmitted from the transmitter 2
Even if the FDM transmission signal has a frequency shift due to the Doppler effect during propagation or the local signal oscillator of the receiver 3 has a frequency shift, a stable and accurate reference carrier frequency fc can be reproduced. can do.

As described above, in this embodiment, the transmitter 2 generates an OFDM transmission signal in which an unmodulated carrier signal (reference signal) is interposed at a fixed period, transmits the signal, and receives the signal. The device 3 receives the OFDM transmission signal, extracts a reference signal included in the OFDM transmission signal, reproduces a 0-degree signal and a 90-degree signal based on the reference signal, and reproduces the 0-degree signal. And the 90-degree signal, the IF signal is subjected to quadrature synchronous detection to reproduce the baseband I signal and the baseband Q signal. Therefore, the OFDM transmitted from the transmitter 2 is received on the receiver 3 side.
It is possible to stably and accurately reproduce a reference carrier frequency fc required for orthogonally synchronous detection of an OFDM signal in a DM transmission signal.

In this embodiment, the length of the frequency lock signal (reference signal) that is intermittently transmitted is set so that the time until the next reference signal is transmitted is divisible. Since the signal generation circuit 6 repeats each reference signal to generate a continuous signal without a break, it is possible to prevent a continuous signal generated from the reference signal extracted on the receiving side from having a break. A more stable continuous signal for frequency lock can be created.

Further, in this embodiment, the reference signal extracted on the receiving side is stored as digital data, and this digital data is repeated and read out, so that it is simpler and simpler than a continuous signal repeated as an analog signal. In addition, a continuous signal for stable frequency locking can be generated.

In this embodiment, even when a part of the frequency locking signal (reference signal) transmitted intermittently is used, a continuous frequency locking signal can be created. Even if the position and length of the transmitted reference signal cannot be accurately obtained on the receiving side, a continuous signal for frequency locking can be created.

FIG. 4 is a block diagram showing an example of a receiver used in another embodiment of the reference carrier frequency recovery system of the orthogonal frequency division multiplex modulation according to the present invention. In this figure, the same parts as those shown in FIG. 3 are denoted by the same reference numerals.

The receiver 3a shown in this figure is different from the receiver 3 shown in FIG. 3 in that a phase adjustment circuit for adjusting the phases of a plurality of reference signals is provided between an fc detection circuit 5 and a repetition signal generation circuit 6. 13 and the phase adjustment circuit 13
c After the phases of the reference signals output from the detection circuit 5 are adjusted to each other, they are added together, and the frequency of the reference signals output from the fc detection circuit 5 is changed due to frequency shift due to the Doppler effect during propagation. The object is to reproduce a stable and accurate reference carrier frequency even if the phase fluctuates.

In this case, as shown in the block diagram of FIG. 5, the phase adjustment circuit 13 operates as shown in FIG.
Detecting a reference signal included in the FDM transmission signal,
The reference signal output intermittently from the fc detection circuit 5 is fetched and, as shown in FIG. 6B, a signal holding circuit 14 for holding the signal and a reference signal of the reference signal held in the signal holding circuit 14 are stored. A phase detection circuit 15 for detecting a phase and generating a phase adjustment signal necessary for matching the phases of these reference signals; and a signal holding circuit 14 based on the phase adjustment signal output from the phase detection circuit 15. The addition circuit 1 generates the reference signals whose phases are aligned as shown in FIG.
6, and fetches a reference signal intermittently output from the fc detection circuit 5, detects the phase of each reference signal while holding the reference signal, and adjusts the phases of these reference signals. And the reference signal obtained as a result is repeatedly supplied to the signal generation circuit 6.

As described above, in this embodiment, the reference signal extracted at the receiving side is generated by aligning the phases of the reference signals and adding them, and this signal is repeated to produce a continuous signal. In addition to the effects of the above-described embodiment, an effect of improving the C / N (signal-to-noise ratio) of a continuous signal used for frequency locking can be obtained. However, a stable and accurate reference frequency can be reproduced.

[0040]

As described above, according to the present invention, according to the first aspect, the signal of the reference carrier frequency which is the center frequency of the OFDM transmission frequency band is provided at a predetermined position in the synchronization signal section of the OFDM signal on the transmission side. , The signal is intermittently transmitted, the signal is taken out on the receiving side, and the signal generated by repeating this signal is used to form a voltage-controlled oscillator loop that locks the frequency. It can be reproduced stably and accurately.

Further, in the second aspect, the ratio between the length of the frequency lock signal intermittently transmitted and the time until the next signal is transmitted is made an integer, thereby extracting the ratio on the receiving side. When the reference signal is repeated, the signal can be a continuous signal without a break in time, and a more stable frequency lock continuous signal can be created.

According to the third aspect of the present invention, the reference signal extracted on the receiving side is stored as digital data, and this data is repeated and read out, so that it is simpler and more stable than a continuous signal repeated as an analog signal. A continuous signal for frequency locking can be created.

According to the fourth aspect of the present invention, a continuous signal for frequency lock is generated by using a part of the signal for frequency lock which is intermittently transmitted. A continuous signal for frequency locking can be created even if the position and length are not accurately obtained.

According to a fifth aspect of the present invention, when a part of the intermittently transmitted frequency lock signal is extracted on the receiving side, the ratio between the cutout length and the time until the next frequency lock signal is extracted is determined. By using an integer, when repeating the reference signal extracted on the receiving side, it is possible to make a continuous signal without a break in time as in claim 2, thereby creating a more stable continuous signal for frequency locking. can do.

According to the sixth aspect of the present invention, a signal obtained by aligning and adding the phase of a reference signal extracted on the receiving side is repeated to generate a continuous signal, thereby providing a C / N (signal pair) of a continuous signal used for frequency locking. Noise ratio)
Even if the noise characteristics on the transmission path are poor, a stable and accurate reference frequency can be reproduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a transmission / reception system to which an embodiment of a reference carrier frequency reproduction method of orthogonal frequency division multiplex modulation according to the present invention is applied.

FIG. 2 is a schematic diagram showing an example of a format of an OFDM transmission signal transmitted from the transmitter shown in FIG. 1 and a format of a continuous signal created on the receiver side.

FIG. 3 is a block diagram illustrating a detailed circuit configuration example of the receiver illustrated in FIG. 1;

FIG. 4 is a block diagram showing an example of a receiver used in another embodiment of a reference carrier frequency reproduction method of orthogonal frequency division multiplex modulation according to the present invention.

5 is a block diagram showing a detailed circuit configuration example of the phase adjustment circuit shown in FIG.

6 is a schematic diagram showing each format example of an OFDM transmission signal received by the receiver shown in FIG. 4, a reference signal extracted on the receiver side, and a continuous signal created on the receiver side.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Transmission / reception system 2 Transmitter 3 Receiver 4, 7 BPF circuit 5 fc detection circuit (reference signal extraction means) 6 Repetition signal creation circuit (continuous signal generation means) 8 Frequency control circuit (voltage control oscillator loop, reference frequency reproduction means) Reference Signs List 9 VCO circuit (voltage-controlled oscillator loop, reference frequency reproduction means) 10 π / 2 phase shift circuit 11, 12 multiplexer circuit 13 Phase adjustment circuit (phase adjustment means) 14 Signal holding circuit 15 Phase detection circuit 16 Addition circuit

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Masayuki Takada 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside the Japan Broadcasting Corporation Research Institute of Broadcasting (72) Inventor Kenichi Tsuchida 1-10-11 Kinuta, Setagaya-ku, Tokyo No. Japan Broadcasting Corporation Broadcasting Research Institute

Claims (6)

[Claims] 1. A reference signal having a reference carrier frequency which is a center frequency of an OFDM transmission frequency band is inserted at a predetermined position in a synchronization signal section constituting an OFDM transmission signal of an OFDM (orthogonal frequency division multiplexing) modulation method. Receiving means for receiving an intermittently transmitted OFDM transmission signal; reference signal extracting means for extracting the reference signal from the received OFDM transmission signal; holding the extracted reference signal; A continuous signal generating means for generating a continuous signal by repeating the held reference signal until the signal is extracted, and a voltage-controlled oscillator loop for locking the frequency using the continuous signal, And reference frequency reproducing means for reproducing a reference carrier frequency for obtaining a baseband I signal and a baseband Q signal. Orthogonal frequency division multiplex modulating a reference carrier frequency reproducing system to. 2. The method according to claim 1, wherein a time interval between the reference signals inserted into the OFDM transmission signal and transmitted intermittently is defined by each reference frequency. The time interval between each reference signal and the time width of each reference signal are determined so that the value obtained by dividing by the signal time width becomes an integer. Reference carrier frequency regeneration method. 3. The reference carrier frequency reproduction method of orthogonal frequency division multiplex modulation according to claim 1, wherein the continuous signal generation means holds digital data obtained by sampling the extracted reference signal, Repeatedly read the held digital data,
A reference carrier frequency reproduction method of orthogonal frequency division multiplex modulation, wherein a pseudo continuous signal is generated. 4. The reference carrier frequency recovery method of orthogonal frequency division multiplex modulation according to claim 1, wherein the continuous signal extracting means is a part of a reference signal intermittently transmitted by being inserted into an OFDM transmission signal. A reference carrier frequency reproduction method for orthogonal frequency division multiplex modulation. 5. The reference carrier frequency recovery method of orthogonal frequency division multiplex modulation according to claim 4, wherein a part of a reference signal inserted intermittently in the OFDM transmission signal and intermittently transmitted is taken out on a receiving side. The time width of the reference signal is determined so that a value obtained by dividing a time interval until the next reference signal is taken out by the extraction time length is an integer. Modulation reference carrier frequency reproduction method. 6. A reference signal having a reference carrier frequency which is a center frequency of an OFDM transmission frequency band is inserted at a predetermined position in a synchronization signal section constituting an OFDM transmission signal of an OFDM (Orthogonal Frequency Division Multiplexing) modulation method. Receiving means for receiving the intermittently transmitted OFDM transmission signal; reference signal extracting means for extracting the reference signal from the received OFDM transmission signal; and holding and holding each of the extracted reference signals. A phase adjusting means for generating a phase-adjusted reference signal by aligning and adding the phases of the respective reference signals, and generating a continuous signal by repeating the phase-adjusted reference signal output from the phase adjusting means. And a voltage-controlled oscillator loop that locks the frequency by using the continuous signal to generate a baseband I of the OFDM signal.
A reference frequency reproducing means for reproducing a signal and a reference carrier frequency for obtaining a baseband Q signal. A reference carrier frequency reproducing method of orthogonal frequency division multiplex modulation, comprising: