JPH02305237A - Signal multiplexing circuit - Google Patents

Abstract

PURPOSE:To prevent a synthesized output from being increased periodically even at non modulation by making the phases of local oscillators in each frequency conversion circuit identical to each other and providing a phase shifting means to each frequency conversion circuit. CONSTITUTION:A synthesizer 5 phase-synchronized to a reference signal oscillator 4 and a phase shifter 6 are provided in a frequency conversion circuit 10a. The phase shift is controlled by the phase shifter 6 to decrease the envelope power of a multiplexing signal obtained from an output port 21. Thus, the phase shift by the phase shifter 6 is set properly to prevent the envelope power of the multiplexing signal from being increased considerably.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a signal multiplexing circuit that combines a plurality of transmission signals having carrier frequencies at constant frequency intervals.

[Conventional Technique #i] FIG. 9 is a block diagram showing the basic configuration of a conventional signal multiplexing circuit.

This conventional circuit linearly combines the respective outputs of a plurality of (n) frequency conversion circuits 10 using a power combining circuit 2o. It has a mixer 7 and a bandpass filter 8.

All local oscillators 2 are shown to operate independently, but in order to improve the frequency accuracy of all local oscillators 2, only one frequency oscillator is provided and its output is distributed as many times as there are signal input terminals. , based on this, each local oscillator may be configured to output a carrier wave of a desired frequency.

In this case, the local oscillator 2 is composed of a synthesizer.

Note that the power combining circuit 20 is a power combining circuit configured with a transformer circuit, a hybrid circuit, and the like.

Next, the operation of the above conventional signal multiplexing circuit will be explained.

Each frequency conversion circuit 10 converts the input signal of the input port 3 into a channel signal of a desired frequency band using the carrier frequency of the local oscillator 2 connected thereto. This converted signal is input to the power combining circuit 20, and the angular frequency ω1 output from each frequency conversion circuit 10,
Channel signals of ω2, . . . , ωn are linearly combined by a power combining circuit 20.

In this case, if the carrier frequencies of the local oscillators 2 are set to different values, signals multiplexed in frequency space can be obtained from the output port 21 of the power combining circuit 20, as shown in FIG.

[Problem to be solved by the invention] When using a conventional signal multiplexing circuit for actual communication, focusing on the envelope power of the multiplexed signal obtained from the output port 21, it is found that the instantaneous phases of each channel signal match. At an instant, the voltages of all channel signals are combined in-phase, so the envelope power increases significantly.

Furthermore, a signal having the same amplitude and the same frequency (hereinafter referred to as "unmodulated signal") is transmitted to all input ports 3.
is applied, the frequency interval Δω of the carrier wave frequency of the local oscillator 2 is constant, and the initial phases match, the output of the frequency conversion circuit 10 becomes an unmodulated signal having a frequency interval of Δω. Therefore, in this case, a state in which all channel signals are in-phase combined occurs periodically.

FIG. 10 is a diagram showing the calculation result of the envelope power of the multiplexed signal obtained from the output port 21 when 10 waves of unmodulated signals are applied to the signal multiplexing circuit under the above conditions.

In this figure, the horizontal axis shows time, and the vertical axis shows the envelope power obtained from the output port 21. however,
T indicates the period of the envelope, T=2π/△ω, and a
Q is the amplitude value of the output signal of the frequency conversion circuit lO,
Zo is the characteristic impedance of the output line of the frequency conversion circuit.

Note that the vertical axis in FIG. 10 is the power a per l channel signal.
It is shown normalized by 2/Zo.

As can be seen from FIG. 10, under the above conditions, the envelope power of the multiplexed signal obtained from the output port 21 is T
The maximum value of the envelope power reaches ioo times the power per channel signal (a2/Zo).

When a conventional signal multiplexing circuit is used under the above conditions, FIG. 3 is a graph showing the relationship between the maximum value of the envelope power obtained from the output port 21 when the power is applied;

In FIG. 12, the horizontal axis indicates the number n of frequency conversion circuits 10 installed, and the vertical axis indicates the maximum value of the envelope power obtained at the output port 21. Here, Po-a
2/Zo, and the vertical axis is normalized by nP6.

As can be seen from FIG. 12, when the number of unmodulated signals is n, the maximum value of the envelope power is also n, and this maximum value is n.
Since it is normalized by P3, the maximum value of the envelope power of the multiplexed signal obtained from the output port 21 is n2Po. This maximum value n2 PG always occurs periodically as shown in FIG.

Therefore, when an amplifier is provided at the output section of a conventional signal multiplexing circuit and the multiplexed signal is amplified with low distortion by the amplifier, the required saturation output of the amplifier is
It is necessary to set the maximum value n2Po of the envelope power of the multiplexed signal or more.

In other words, the problem with the above conventional circuit is that when all the local oscillators provided in multiple frequency conversion circuits operate in phase with each other, their conversion outputs are synthesized in phase by a synthesis circuit, resulting in a periodic increase in the output. There is. Furthermore, if the local oscillators are operated independently, there is a problem in that depending on the timing of power-on, a state in which the output increases periodically may occur stochastically.

The present invention deals with combining a plurality of transmission signals having carrier frequencies at constant frequency intervals, and when the number of unmodulated signals to be multiplexed increases, the output envelope power increases significantly. The object of the present invention is to provide a signal multiplexing circuit that prevents this.

[Means for Solving the Problems] A first aspect of the present invention provides a signal multiplexing circuit having one oscillator, a plurality of frequency converting means, and a power combining means for combining each frequency-converted signal. All the local oscillators in the frequency conversion circuit have the same phase, and each frequency conversion circuit is provided with a phase shifting means.

Further, a second aspect of the present invention includes one oscillator, a plurality of frequency modulation means, a plurality of phase shift means for making the phases of each frequency modulated signal different from each other, and output signals of these phase shift means. and a power combining means for combining.

[Function 1] The first aspect of the present invention is that the phases of the local oscillators in each frequency conversion circuit are all the same, and if the phase shifting means is adjusted so that the phases of the output signals of each frequency conversion circuit are different from each other, power synthesis is possible. All the signals in the circuit do not have the same phase with each other, so even when no modulation is performed, it is possible to prevent the combined output from increasing periodically.

Further, in the second aspect of the present invention, if the phase shift means is adjusted so that the phases of the frequency-modulated signals are different from each other, all the signals in the power combining circuit will not have the same phase with each other. , even when no modulation is performed, it is possible to prevent the combined output from increasing periodically.

[Embodiment] FIG. 1 is a block diagram showing the configuration of a signal multiplexing circuit according to a first embodiment of the first invention.

Note that the same members are given the same reference numerals. The same applies to other embodiments.

This embodiment includes one reference frequency oscillator 4, a plurality of frequency conversion circuits 10a, and a power synthesis circuit 20 that combines the power of each output signal of the plurality of frequency conversion circuits 10a.

The frequency conversion circuit 10a includes a synthesizer 5 that receives an input signal from the input port 3 and synchronizes the phase with the reference frequency oscillator 4, a phase shifter 6, a mixer 7, and a bandpass filter 8.

Here, if a PLL type frequency synthesizer is used as the synthesizer 5, the initial phase of its output signal can be synchronized with the output signal of the reference frequency oscillator 4. Further, the synthesizer 5 is an example of oscillation means driven by an oscillator.

The phase shifter 6 is a well-known component that can be composed of a circulator, a variable delay line, a varactor diode, etc.
(See p. 21, Institute of Electronics and Communication Engineers, 1981). Further, the phase shifter 6 is an example of a phase shifter that changes the phase of the signal frequency-converted by the frequency mixer.

The mixer 7 is an example of a frequency mixing means that converts the frequency of an input signal using the output signal of the oscillation means, and the bandpass filter 8 is a bandpass filtering means that removes a predetermined frequency component from the output of the frequency mixing means. This is an example.

Further, three or more frequency converting means are provided, and the phase of the oscillating means provided in one frequency converting means and the phase of the oscillating means provided in the other frequency converting means are set to be the same, and , the phases of the output signals of the respective frequency conversion circuits are made different from each other by the phase shifting means.

The first embodiment differs from the conventional example in that the frequency conversion circuit 10a includes a synthesizer 5 whose phase is synchronized with the reference signal oscillator 4 and a phase shifter 6.

Next, the operation of the above embodiment will be explained.

First, the number of non-modulated signals to be multiplexed is set to n (n≧3), and the synthesizer 5 in the second frequency conversion circuit 10a
The output signal voltage gp of gp = Ac cosΩP
Let it be t-(1). However, p=1.2',
... n, AC indicates amplitude, and Ωp indicates angular frequency.

At this point, since the initial phases of the outputs of all the synthesizers 5 match each other, the outputs of the mixer 7
After being frequency mixed with the unmodulated signal at
The output voltage f of the i-th frequency conversion circuit 10a filtered by
')...(2) can be set. However, A is the amplitude and ωp
is the angular frequency, θ0 is the initial phase of the output of the synthesizer 5, and θ represents the amount of phase shift by 1 by the phase shifter 6.

Here, since no woody difference occurs even when θ0=0, the phase term in equation (2) is changed to f p'='Ae c
Let o s (ω, t 10, )...(3). Then, when an unmodulated signal is applied to the input port 3, the multiplexed signal voltage f obtained from the output port 21 after power synthesis is performed by the power combining circuit 20 is as follows: f=ΣA, CO5((+)11 t +0.)p
=t (4).

Here, if we use vector representation, (3) formula% formula%)) Similarly, if we use vector representation, equation (4) becomes ... (6) becomes.

Furthermore, the envelope power of the multiplexed signal obtained from the output port 21 is determined. Therefore, when the square of the effective voltage value is calculated using equation (6), it is as follows. However, the operator "." represents the inner product of vectors. If the angular frequency quotient interval △ω of the carrier wave frequency by the Shin-eliminating Iza 5 is constant, then for each angular frequency: 24. -6. =-6-'(8) can be set. , where p'=1.2. ...
It is n. Therefore, equation (7) is: 1 F l 2= n Am? + 2 Am2cO5((n-1)△ωt+I9n
-01)・,・(9)

At this time, in order to eliminate the second term on the right side, the phase shift amount of the phase shifter 6 is controlled so that θp-1-〇, = 2π/, (n-, 1,).

Controlling the amount of phase shift by the phase shifter 6 in this way
This is a feature of the first embodiment, that is, it is necessary to set the phase difference between signals of adjacent frequencies to the above value. As an example of this, 00-
〇If I=0, θp −((P-1)(P-2)/
It is sufficient to set (n-1)hr −= (10). However, p=1.2. ...n.

With this setting, the square of the effective voltage value can be reduced by the second term on the right side of equation (9).

FIG. 2 is a diagram showing calculation results of the envelope &l power of the multiplexed signal obtained from the output port 21 in the first embodiment.

In this Figure 2, the horizontal and vertical axes represent the first
These are consistent with those in Figure 0.

In FIG. 2, since the second term on the right side of equation (9) has been eliminated, the maximum value of the envelope power of the multiplexed signal obtained from the output coupler 21 is approximately 5 1.15 ( 0,
19). However, since the third term and subsequent terms on the right side of equation (9) remain, some periodicity remains.

FIG. 3 shows the number n of unmodulated signals applied to the input port 3 and the number n of non-modulated signals applied to the input port 3 when the phase shift amount of the phase shifter 6 is set as described above in the first embodiment. It is a graph which shows the relationship with the maximum value of the envelope power of the multiplexed signal obtained from the output port 21, and is a figure which shows the result calculated using Formula (9).

Note that the horizontal and vertical axes in FIG. 3 correspond to those in FIG. 12, which shows a conventional example.

In the first embodiment, as shown in FIG. 3, if PG is the power per channel signal, the maximum value of the multiplexed signal is approximately 1. ．． It becomes 9nPo.

Although the above description deals with the case where the phase shift amount of the phase shifter 6 is set as shown in equation (10), the phase shift amount of the phase shifter 6 may be set using other methods. For example, the amount of phase shift of the phase shifter 6 may be set so as to eliminate the third term on the right side of equation (9).

According to the first embodiment, even if the frequency interval of the carrier frequencies by the synthesizer 5 is constant, the envelope power of the multiplexed signal is significantly increased by appropriately setting the amount of phase shift by the phase shifter 6. can be prevented from happening.

FIG. 4 is a block diagram showing a second embodiment of the first invention.

In this second embodiment, a single frequency conversion circuit 10b is provided in place of the frequency conversion circuit 10a, and this frequency conversion circuit 10b is provided with a phase shifter 6 after a bandpass filter 8. .

Even if the frequency conversion circuit 10b is provided in place of the frequency conversion circuit 10a, if the input is a non-modulated signal.

Since the output of the mixer 7 becomes a non-modulated signal, the phase of the signal input to the power combining circuit 20 can be adjusted.

Therefore, if the phase shift amount of the phase shifter 6 is set in advance according to the number of non-modulated signals to be multiplexed using equation (10), then
Similar to the signal multiplexing circuit shown in FIG. 1, it is possible to prevent the envelope power of the multiplexed signal from increasing significantly.

FIG. 5 is a block diagram showing a third embodiment of the first invention.

In this third embodiment, a frequency conversion circuit 10c is provided in place of the frequency conversion circuit 10a, and this frequency conversion circuit 10c is provided with a phase shifter 6 in front of a bandpass filter 8. be. The case where the phase shifter 6 is provided before the bandpass filter 8 in this way can also be explained in the same manner as the second embodiment shown in FIG.

FIG. 6 is a block diagram showing a fourth embodiment of the first invention.

In this fourth embodiment, a frequency conversion circuit 10d is provided in place of the frequency conversion circuit 10a, and this frequency conversion circuit 10d has attenuators R1 and R2 in the frequency conversion circuit 10b of the second embodiment. It has been established.

In the first embodiment, the effect is noticeable when the amplitude of the input signal of the frequency conversion circuit 10a and the amplitude of the output signal of the synthesizer 5 are equal, but when the amplitudes of both signals are not equal, Both signals may be made to have equal amplitude by attenuators R1 and R2 provided in the frequency conversion circuit 10d. Further, either of the attenuators R1 and R2 may be omitted, and an amplifier may be provided in place of the attenuators R1 and R2.

The first invention is characterized in that the frequency conversion circuit is provided with a phase shifting function, and there are no restrictions on the installation position of the phase shifter. Therefore, the phase shifter may be provided immediately after the local oscillator as described above, may be provided at the rear of the mixer, or may be provided at the rear of the bandpass filter. This is because in any of the above cases, the unmodulated signal passes through the phase shifter.
This is because the effects are the same.

FIG. 7 is a diagram showing a preferred application example of the first embodiment.

This application example includes a narrowband filter 31 that detects the power of an output signal of a specific frequency, an envelope detector 32, and a control section 30.
This is an addition to the embodiment shown in FIG.

In this application example, only a signal of a specific frequency passes through the narrowband filter 31, the detector 32 detects the passed signal, and the control unit 30 detects the detected voltage. Based on this detected voltage, the frequency conversion circuit 10
A control unit 30 controls the phase shifter 6 of a. Note that the control unit 30 controls the center frequency of the narrowband filter 31.

In the application example shown in FIG. 7, frequency conversion circuits iob, ioc, and 10d may be provided in place of the frequency conversion circuit 10a.

FIG. 8 is a block diagram showing an embodiment of the second invention.

The signal multiplexing circuit of this embodiment includes one reference frequency oscillator 4, a plurality of n (n≧3) frequency modulation circuits 40,
a phase shifter 6 that shifts the phase of the output signal of the frequency modulation circuit 40;
The power combining circuit 20 linearly combines the output signals of the phase shifter 6.

The frequency modulation circuit 40 receives a signal from the input port 3, and includes a frequency divider 43 that divides the frequency of the output signal of a voltage controlled oscillator (V C0) 46, which will be described later, and a frequency divider 43 that divides the output signal of the reference frequency oscillator 4 and divides the frequency. It has a phase comparator 44 for comparing the phase of the output of the converter 43, a low pass filter (LPF) 45, and a voltage controlled oscillator 46.

Note that the frequency division ratios of the frequency dividers 43 in each frequency modulation circuit 40 are set to different values. Further, the amount of phase shift of each phase shifter 6 is set according to the number of non-modulated signals to be multiplexed using equation (10).

Next, the operation of the embodiment shown in FIG. 8 will be explained.

First, based on the signal from the reference frequency oscillator 4, the frequency divider 4
A frequency division ratio of 3 generates a channel signal in the desired frequency band. The voltage controlled oscillator 46 outputs a modulated signal based on this channel signal and the signal input from the input port 3.

The output signal of the frequency modulation circuit 40 is phase-shifted by the phase shifter 6, and then input to the power combining circuit 20, where it is linearly combined.

Since the frequency division ratios of the respective frequency dividers 43 are set to different values, the output port 21 of the power combining circuit 20 generates an output signal multiplexed in frequency space.

When no signal is input to the input port 3 (that is, when a DC voltage is applied), the output of the modulation circuit 40 becomes an unmodulated signal, which is the same as the explanation in FIG. 1.

Therefore, if the phase shift amount of each phase shifter 6 is set according to the number of non-modulated signals to be multiplexed using equation (10), the same effect as the signal multiplexing circuit shown in FIG. 1 can be obtained. I can do it.

[Effects of the Invention] According to the present invention, it is possible to prevent the envelope power of multiplexed signals from increasing significantly. When applied to a multicarrier transmitter, the effect is that the required saturation output of the amplifier can be significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of the first invention. FIG. 2 is a diagram showing the output characteristics of the signal multiplexing circuit in the above embodiment. FIG. 3 is a diagram showing the relationship between the number of non-modulated signals applied and the maximum value of the envelope power of the multiplexed signal when the first invention is used. FIG. 4 is a block diagram showing a second embodiment of the first invention. FIG. 5 is a block diagram showing a third embodiment of the first invention. FIG. 6 is a block diagram showing a fourth embodiment of the first invention. FIG. 7 is a block diagram showing an example of application of the first embodiment of the first invention. FIG. 8 is a block diagram showing an embodiment of the second invention. FIG. 9 is a block diagram showing a conventional signal multiplexing circuit. FIG. 10 is a diagram showing the output characteristics of the conventional circuit. FIG. 11 is an explanatory diagram of a multiplexed signal multiplexed in frequency space. FIG. 12 is a diagram showing the relationship between the number of non-modulated signals applied and the maximum value of the envelope power of the multiplexed signal in the conventional example. 3...Signal input port, 4...Reference signal oscillator, 5...Synthesizer, 6...Phase shifter, 7...Mixer, 8...Band filter, 10a, iob, 10 c-frequency conversion circuit, 20...
・Power combining circuit, 43... Frequency divider. 44... Phase comparator, 45... Low pass filter, 46... Voltage controlled oscillator, 40... Frequency conversion circuit. Patent applicant: Japan Telegraph and Telephone Co., Ltd. Agent
Arata Yokubo - (OduX) 1 and ￥'2＠Qri [4! l&'JJWQ
Sect ■

Claims (2)

[Claims] (1) In a signal multiplexing circuit having one oscillator, a plurality of frequency conversion means, and a power synthesis means for synthesizing the frequency-converted signals, an oscillation means driven by the oscillator; an output of the oscillation means; frequency mixing means for converting the frequency of an input signal according to the signal; bandpass filtering means for removing a predetermined frequency component from the output of the frequency mixing means; changing the phase of the signal frequency-converted by the frequency mixing means; The frequency converting means has a phase shifting means;
or more, and the phase of the oscillation means provided in one of the frequency conversion means and the phase of the oscillation means provided in another of the frequency conversion means are set to be the same. Multiplexing circuit. (2) one oscillator; three or more frequency modulation means driven by this oscillator; three or more phase shift means for respectively changing the phase of each signal frequency modulated by these frequency modulation means; A signal multiplexing circuit comprising: power combining means for combining output signals of the phase shifting means;