JPH0878967A - Negative feedback amplifier - Google Patents

Abstract

PURPOSE: To provide the oblique type negative feedback amplifier with which distortion caused by phase delay or advance is compensated by feedback control. CONSTITUTION: Concerning this oblique type negative feedback amplifier, the basic circuit is composed of subtracters 103 and 104, band limit circuits 105 and 106, oscillator 107, orthogonal modulator 108, amplifier 109, attenuator 110 and orthogonal demodulator 112. A phase shifter 111 changes the phase of a carrier wave signal L2a to be supplied to the orthogonal demodulator 112 corresponding to a phase control signal PCa. A phase control circuit 113 receives input base band signals I and Q and feedback base band signals F1 and FQ, for which an orthogonally modulated signal Mc from the amplifier 109 is demodulated by the orthogonal demodulator 112, and outputs the phase control signal PCa for decreasing the phase shift amount of the phase shifter 111 when the phases of these feedback band signal vectors are delayed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negative feedback amplifier for compensating for non-linear distortion of an amplifier for amplifying a quadrature modulation signal, and more particularly to a Cartesian for compensating for distortion by demodulating the output of the amplifier and negatively feeding it back in the form of a baseband signal. Type negative feedback amplifier.

[0002]

2. Description of the Related Art A conventional negative feedback amplifier of this type has a 4-phase P-type.
When performing high-density wireless digital transmission using a linear modulation method such as SK or 16-valued QAM, a method for compensating for nonlinear distortion of a power amplifier in a transmitter, especially a high loopback for a modulation signal in a high frequency band It is known as a method for obtaining a gain.

Regarding the negative feedback amplifier disclosed in Japanese Patent Laid-Open No. 5-58283, a block diagram of a conventional negative feedback amplifier shown in FIG. 6 and a quadrature modulator 108 and a quadrature demodulator 112 shown in FIG. Description will be given with reference to a block diagram and a vector diagram of the input baseband signal and the feedback baseband signal shown in FIG.

In this feedback amplifier, terminals 101 and 102 receive an input baseband signal I represented by a function x (t) and an input baseband signal Q represented by a function y (t), respectively. Subtractors 103 and 10
4 subtracts the feedback baseband signals FIx and FQx from the input baseband signals I and Q, respectively, and produces subtracted baseband signals Iax and Qax, respectively. The subtracted baseband signals Iax and Qax are band-limited by the band limiting circuits 105 and 106, respectively, and the modulated signal I represented by the function x1 (t) is obtained.
modulation signal Qbx represented by bx and the function y1 (t)
become.

The quadrature modulator 108 quadrature-modulates the carrier signal L1 of the angular frequency ωc generated by the oscillator 107 with the modulation signals Ibx and Qbx, and the function z (t) = x1.
The quadrature modulation signal Max represented by (t) · cosωct + y1 (t) · sinωct is generated. This quadrature modulation system uses QPSK (4-phase phase shift keying), π /
4-shift QPSK or 16-value QAM modulation or the like.
Further, the oscillator 107 has a frequency f (= ωc / 2π) of 90 if the application of this negative feedback amplifier is a car telephone system.
A carrier signal L1 in the 0 MHz band, 140 MHz band in the case of a commercial radio system is generated.

The quadrature modulator 108, as shown in FIG. 7A, multiplies the modulation signal Ibx by the carrier signal L1 and the modulation signal Ibx and the phase shifter 84 to generate the carrier signal L1 by 90. It has a multiplier 82 that multiplies the signal delayed by a degree, and an adder 83 that adds the output of the multiplier 81 and the output of the multiplier 82 to generate a quadrature modulation signal Max.

The quadrature modulation signal Max is amplified by the amplifier 109 into a quadrature modulation signal Mbx. Quadrature modulation signal M
Most of bx is radiated from the antenna, and this signal Mbx
A part of the attenuator 110 is branched by a directional coupler or the like.
Is supplied to. The attenuator 110 attenuates the quadrature modulation signal Mbx to a predetermined level and supplies the quadrature modulation signal Mcx to the quadrature demodulator 112. The quadrature demodulator 112 quadrature-modulates in response to the carrier signal L2ax and the quadrature modulation signal Mcx, which are phase-shifted (phase-shifted) by the phase shifter 302, the carrier signal L2 (the same signal as the signal L1) supplied from the oscillator 107. The signal Mcx is demodulated to produce a feedback baseband signal FIx corresponding to the input baseband signal I and a feedback baseband signal FQx corresponding to the input baseband signal Q.

The quadrature demodulator 112, as shown in FIG. 7B, multiplies the modulation signal Mcx and the carrier signal L2ax to generate the feedback baseband signal FIx.
22 and a multiplier 123 that produces a feedback baseband signal FQx by multiplying the modulation signal Mcx by a signal obtained by delaying the carrier signal L2ax by 90 degrees by the phase shifter 121.

The feedback baseband signals FIx and FQx output from the quadrature demodulator 112 are subjected to amplitude distortion and phase distortion due to the non-linear distortion of the amplifier 109. The feedback baseband signals FIx and FQx are subtracted as described above. The amplifier 10 by supplying the amplifiers 103 and 104.
By negatively feeding back the nonlinear distortion component of 9, the negative feedback amplifier compensates the nonlinear distortion of the amplifier 109.

The above-described negative feedback amplifier obtained by removing the phase difference detection circuit 301 from the circuit of FIG. 6 generally produces a quadrature modulation signal Max due to the loop length of the negative feedback circuit, the band-limited frequency characteristic of the power amplifier 109, and the like. Compared with this, the quadrature modulation signal Mcx is delayed, and the carrier phases of both signals are different from each other. For example, the amount of phase shift of the phase shifter 302 is fixed, and the amount of delay from the output end of the quadrature modulator 108 to the input end of the quadrature demodulator 112 changes due to temperature characteristic variations of the amplifier 109, load variations of the antenna, and the like. Then, with respect to the input baseband signal vector (see FIG. 8A) which is a combined vector of the quadrature modulated signals I and Q, the feedback baseband signal FI
And a feedback baseband signal vector (see FIG. 8B), which is a combined vector of FQ, causes phase rotation. As a result, the distortion suppression characteristic of this negative feedback amplifier deteriorates.

Therefore, the disclosed negative feedback amplifier receives a part of the quadrature modulation signal Max and the quadrature modulation signal Mcx by the phase difference detection circuit 301 and outputs a phase difference signal PCx representing the phase difference Δθ between the two. . This phase difference signal PCx
Is supplied to the phase shifter 302, and the phase shifter 302 outputs the phase difference Δθ.
The amount of phase shift is changed so that becomes minimum. As a result of this control, the vector phases of the quadrature modulation signal Max and the quadrature modulation signal Mcx substantially coincide with each other, and this negative feedback amplifier can reduce the deterioration of nonlinear distortion due to the above-described phase rotation characteristic.

[0012]

However, the above-described negative feedback amplifier according to the prior art has the quadrature modulation signals Max and Mc.
Since the feedforward (open loop) control is performed for the phase control with respect to x, the above-mentioned phase control cannot be sufficiently performed unless the phase difference detection accuracy of the phase difference detection circuit is sufficient. There is a drawback that it is difficult to sufficiently reduce distortion deterioration.

Further, when the signal delay amount between the quadrature modulated signals Max and Mcx is large, this delay inevitably causes an error in the phase difference detection, and similarly, the distortion deterioration due to the phase rotation characteristic is reduced. It had the drawback of being difficult.

[0014]

A negative feedback amplifier in accordance with the present invention comprises a first and a second input baseband signal to a first
First and second subtractors for respectively subtracting the first and second feedback baseband signals to produce first and second subtraction baseband signals, respectively, and banding the first and second subtraction baseband signals, respectively. First and second band limiting circuits for limiting and producing first and second modulated signals respectively, an oscillator for producing a carrier signal, said first
And a quadrature modulator that modulates the carrier signal with a second modulation signal to generate a quadrature modulated signal, an amplifier that amplifies the quadrature modulated signal, the carrier signal and a portion of the quadrature modulated signal from the amplifier. In response to demodulating the quadrature modulated signal, the first feedback baseband signal corresponding to the first input baseband signal and the second feedback baseband signal corresponding to the second input baseband signal. In a negative feedback amplifier including a quadrature demodulator, the phase shifter that shifts the phase of the carrier signal supplied to the quadrature demodulator by a phase control signal, and the first and second feedback baseband signals, respectively. The first and second input basebands with respect to the phase of a feedback baseband signal response vector, which is a composite vector of responding baseband signals And a phase control circuit to produce the phase control signal corresponding to the phase of the lag-lead input baseband signal vector is a composite vector of the item.

In one of the negative feedback amplifiers, the baseband signals responsive to the first and second feedback baseband signals are the first and second feedback baseband signals themselves, and the phase control is performed. When the phase of the vector of the feedback baseband signal is delayed from the phase of the input baseband signal vector, the signal reduces the phase shift amount of the phase shifter and the phase of the vector of the feedback baseband signal is When the phase of the input baseband signal vector is advanced, the phase shift amount of the phase shifter can be increased.

Another one of the negative feedback amplifiers is the first feedback amplifier.
And the baseband signals respectively responsive to the second feedback baseband signal are the first and second modulated signals, and the phase control signal is the phase of the vector of the modulated signal of the input baseband signal vector. The phase shift amount of the phase shifter is increased when the phase is delayed, and the phase shift amount of the phase shifter is advanced when the phase of the vector of the modulation signal is ahead of the phase of the input baseband signal vector. Can be reduced.

In still another one of the negative feedback amplifiers, the phase control circuit has the input baseband signal whose zero crossing direction does not cross zero crossing at the instant of zero crossing of the first and second input baseband signals. And determining the lead or lag of the phase between the input baseband signal vector and the feedback baseband signal response vector in response to the respective polarities of the baseband signals of the first and second feedback baseband signal responses. A configuration for generating the phase control signal can be adopted.

In the negative feedback amplifier, the phase control circuit is
A limiter for receiving the first and second input baseband signals and the baseband signals of the first and second feedback baseband signal responses and producing a polarity signal indicating a polarity thereof, and the first and second inputs In response to the input baseband signal and the polarity signal of the baseband signal of the first and second feedback baseband signal responses, which is the direction of zero-crossing at the instant when the polarity signal corresponding to the baseband signal zero-crosses and which does not zero-cross. A phase rotation determination circuit that generates a phase delay advance signal and a counter operation signal indicating a phase advance or delay between the input baseband signal vector and the feedback baseband signal response vector, and the phase for each input of the counter operation signal. Count up or down the count output according to the delay signal That the counter and can be the structure having a phase shift amount setting circuit to produce the phase control signal corresponding to the count output.

[0019]

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment according to the present invention. 2A and 2B are vector diagrams for explaining the present embodiment. FIG. 2A shows an input baseband signal vector, and FIG. 2B shows a feedback baseband signal vector.

The negative feedback amplifier of this embodiment has the same terminal 1 as the negative feedback amplifier according to the prior art shown in FIG.
01, 102, subtractors 103, 104, band limiting circuits 105, 106, oscillator 107, quadrature modulator 108, amplifier 109, attenuator 110, and quadrature demodulator 112. In addition, this negative feedback amplifier is a conventional phase shifter 30.
Instead of 2, the phase shifter 111 is provided, and the phase difference detection circuit 301 is omitted and a phase control circuit 113 is provided instead. The above-mentioned circuits also used in the conventional negative feedback amplifier operate in the same manner in this embodiment, but input / output signals having different characteristics are represented by symbols without the suffix x.

The negative feedback amplifier of this embodiment also inputs the input baseband signals I and Q to the terminals 101 and 102, respectively, as in the conventional negative feedback amplifier. The subtractors 103 and 104 receive the input baseband signal I
And Q subtract the feedback baseband signals FI and FQ to produce subtracted baseband signals Ia and Qa, respectively. The subtracted baseband signals Ia and Qa are band-limited by band limiting circuits 105 and 106, respectively, and become modulated signals Ib and Qb, respectively. In addition,
The modulated signals Ib and Qb are the feedback baseband signal FI.
And a baseband signal that responds to FQ, respectively.

The quadrature modulator 108 quadrature modulates the carrier signal L1 generated by the oscillator 107 with the modulation signals Ib and Qb to generate a quadrature modulation signal Ma. The quadrature modulation signal Ma is power-amplified by the amplifier 109 and becomes a quadrature modulation signal Mb. Most of the quadrature modulation signal Mb is radiated from the antenna, and a part of this signal Mb is branched by a directional coupler or the like and supplied to the attenuator 110. Attenuator 110
Reduces the quadrature modulation signal Mb to a predetermined level and supplies the quadrature modulation signal Mc to the quadrature demodulator 112. The quadrature demodulator 112 is a carrier signal L2 obtained by shifting the phase of the carrier signal L2 generated by the oscillator 107 by the phase shifter 111.
2a and quadrature modulation signal Mc in response to quadrature modulation signal Mc
Are demodulated to produce a feedback baseband signal FI corresponding to the input baseband signal I and a feedback baseband signal FQ corresponding to the input baseband signal Q. The quadrature modulator 108 and the quadrature demodulator 112 also have the configuration shown in FIG. 7.

Now, the negative feedback amplifier of this embodiment has a phase shifter 11 inserted between the oscillator 107 and the quadrature demodulator 112.
1 is feedback-controlled by the phase control signal PCa. That is, the phase control circuit 113 firstly outputs the input baseband signal vector, which is a composite vector of the input baseband signals I and Q, and the feedback baseband signal FI.
The phase difference between the feedback baseband signal vector, which is a composite vector of FQ and FQ, is detected. Then, the phase control circuit 1
13 reduces the amount of phase shift of the phase shifter 111 when the phase of the feedback baseband signal vector is behind the input baseband signal vector, and the phase of the feedback baseband signal vector is the input baseband. When the phase is advanced from the phase of the signal vector, the phase control signal PCa for increasing the phase shift amount of the phase shifter 111 is generated.

For example, the phase control circuit 113 detects the direction of rotation of the input baseband signal vector when the input baseband signal vector crosses the I axis or the Q axis, and the quadrant in which the feedback baseband signal vector is located at that time. Due to
A phase delay between the input baseband signal vector and the feedback baseband signal is determined. The phase control circuit 113 outputs the phase control signal PCa corresponding to the determination result of the phase lag / advance between the two vectors, and the phase shifter 1
The phase shift amount of 11 is controlled.

The phase lag / lead determination will be described with reference to FIG. 2. When the input baseband signal vector crosses the Q axis (see FIG. (A)), the feedback baseband signal vector is in the first quadrant. (See Figure (b)).
The input baseband signal vector is from the second quadrant to the first
When moving to the quadrant, the phase control circuit 113 determines that the feedback baseband signal vector leads the input baseband signal vector, and the phase shifter 11
The phase control signal PCa for reducing the phase shift amount of 1 is output. Conversely, when the input baseband signal vector moves from the first quadrant to the second quadrant, the phase control circuit 113 determines that the feedback baseband signal vector is delayed in phase from the input baseband signal vector. The phase control signal PCa for increasing the phase shift amount of the phase shifter 111 is output. As described above, by sequentially controlling the phase amount of the phase shifter 111 every time the input baseband signal vector crosses the I axis or the Q axis, the phase of the carrier signal L2a supplied to the quadrature demodulator 112 is sequentially corrected. can do.

By the above operation, the negative feedback amplifier of this embodiment realizes the feedback type phase shifter 111 control.

Although the embodiment of FIG. 1 controls the phase shifter 111 when the input baseband signal vector crosses the I axis or Q axis in FIG. 2, the feedback baseband signal vector is I axis or Q axis. Obviously, the phase shifter control similar to that of the embodiment of FIG. 1 can be performed even if the above-described phase delay advance determination is performed when the axis is crossed. Further, when the negative feedback amplifier is configured to perform the phase shifter control by performing the phase lag / lead determination each time the input baseband signal vector and the feedback baseband signal vector cross the I axis or the Q axis, respectively. The phase shifter control can be performed at twice the frequency of the first embodiment, and the convergence speed of the phase rotation correction can be accelerated.

FIG. 3 is a block diagram of the phase control circuit 113 used in the embodiment of FIG. FIG. 4 is a signal waveform diagram of main signals in the phase control circuit 113.

Phase control circuit 113 inputs input baseband signals I and Q received at terminals 601 and 602 to limiters 605 and 606, respectively, and terminal 603.
The feedback basebands FI and F received by Tobi 604
Q is input to limiters 607 and 608, respectively.
Each of the limiters 605 to 608 limits and shapes the input signal to the limiter 605, and outputs polarity signals Is, Qs, FIs and FQs indicating the polarity of the input signal, respectively. In this circuit 113, an H-level polarity signal is generated when the input signal has a positive polarity, and an L-level polarity signal is generated when the input signal has a negative polarity.

The phase rotation determination circuit 609 is provided with the polarity signals Is and Qs of the input baseband signals I and Q corresponding to the input baseband signal vector and the feedback baseband signal F corresponding to the feedback baseband signal vector.
Receiving the polarity signals FIs and FQs of I and FQ, first, the phase delay of the feedback baseband signal vector with respect to the input baseband signal vector is determined. This judgment table is shown in Table 1. Phase (-) indicates that the phase of the feedback baseband signal vector is delayed with respect to the input baseband signal vector, and phase (+) indicates that the phase of the feedback baseband signal vector is advanced. .

[0032]

[Table 1]

This phase delay advance judgment is performed when the polarity signals Is and Qs cross zero. From Table 1, the phase rotation determination circuit 609 indicates that the direction of the zero cross of the polarity signal Is or Qs, that is, the direction in which the input baseband signal vector composed of the input baseband signals I and Q crosses the I axis or the Q axis of FIG. , All polarity signals Is, Q
quadrant of the input baseband signal vector obtained using s, FIs and FQs and the feedback baseband signal FI
It can be seen that the lag / advance of the phase is determined from the quadrant having the feedback baseband signal vector composed of FQ and FQ.

The phase rotation judgment circuit 609 outputs the result of this phase delay advance judgment as the H level for the phase delay and the L level for the phase advance.
Output as a phase lag / lead signal D of the level, and also input baseband signals I (and polarity signals Is) and Q
The counter operation signal Cd is output only when (and the polarity signal Qs) zero-crosses.

The phase delay advance signal D and the counter operation signal Cd are supplied to the counter 610. Counter 610
Operates only when the counter operation signal Cd is ON,
Counts up when the phase delay lead signal D is at H level, that is, when the feedback baseband signal vector is delayed with respect to the input baseband signal vector,
When the phase delay advance signal D is at L level, that is, when the feedback baseband signal vector is advanced, the countdown is performed, and the N (N is an integer) signal line outputs the N-bit count value C. The counter value C is a value corresponding to the phase around the feedback baseband signal vector with respect to the input baseband signal vector.

The count value C is supplied to the sine wave table 611 and the cosine wave table 612. The sine wave table 611 stores the sine value corresponding to the counter value C, and the cosine wave table 612 stores the cosine value corresponding to the count value C. The counter value C and the phase information output from the tables 611 and 612 are, for example, 2π when the N signal values of the count value C are all 1 and 0 (radii) when all the signal values are 0.
By making it correspond to (an), it becomes possible to make a relationship in 2π / N steps. The sine wave table 61
1 and cosine wave table 612 are stored in ROM (Read On
It can be easily configured by ly Memory). The output of the sine wave table 611 is supplied to the D / A converter 613, and the output of the cosine wave table 612 is supplied to the D / A converter 614. The D / A converter 613 outputs the phase control signal PCa (I) corresponding to the output of the sine wave table 611, that is, the phase around the I axis of the feedback baseband signal.
p) and the D / A converter 614 is delayed by 90 degrees from the output of the sine wave table 611, and therefore outputs the phase control signal PCa (Qp) corresponding to the phase around the Q axis of the feedback baseband signal. This phase control voltage PCa
Controls the phase shift amount (phase shift amount) of the phase shifter 111.

Here, since the phase control circuit 113 outputs two phase control signals Ip and Qp as the phase control signal PCa, the phase shifter 111 controlled by the phase control signal PCa is shown in FIG. ) Quadrature modulator 10
It is preferable to use 8. Signal I of quadrature modulator 108
The phase control signal Ip is input to the b input terminal, the phase control signal Qp is input to the signal Qb input terminal, and the carrier signal L is input to the carrier signal L1 input terminal.
2 is supplied, the phase of the carrier signal L2 is output to the output terminal of the quadrature modulation signal Ma from the table 611 corresponding to the count value C.
And a carrier signal L2a whose phase is shifted by the phase θ stored in 612 is generated. The phase shifter 111 may be of a type that changes the amount of phase shift of the high frequency signal by changing the voltage of a varactor or the like. When this type of phase shifter 111 is used, only one of Ip and Qp may be used as the phase control signal PCa.

FIG. 5 is a block diagram of the second embodiment according to the present invention.

This negative feedback amplifier has substantially the same operation principle and constituent elements as those of the embodiment of FIG. 1, but the phase control circuit 113A of this embodiment band-limits the phase information of the feedback baseband signals FI and FQ. The outputs of the circuits 105 and 106, and the feedback baseband signals FI and F
It is derived from the modulated signals Ib and Qb responsive to Q. Here, the feedback baseband signals FI and FQ and the modulation signals Ib and Qb are subtracted by the subtractors 103 and 10
The phase relationship with respect to the input baseband signals I and Q is reversed depending on whether or not 4 has passed. Therefore, the phase control circuit 113A shifts the phase shifter when the phase of the modulation signal vector (feedback baseband signal response vector), which is a combined vector of the modulation signals Ib and Qb, is behind the phase of the input baseband signal vector. When the phase of the modulation signal vector leads the phase of the input baseband signal vector, the phase shift amount of the phase shifter 111 must be increased.

Therefore, the phase control circuit 113A having substantially the same function as the phase control circuit 113 first receives the input baseband signals I and Q and the modulation signals Ib and Qb, and receives the input baseband signal vector and the modulation signal vector. Detects the phase lag advance between and. However, the counter incorporated in the phase control circuit 113A counts down the counter operation signal when the modulation signal vector is delayed with respect to the input baseband signal vector, and counts up when the modulation signal vector is advanced. . A phase shift amount setting circuit including a sine wave table, a cosine wave table, and two D / A converters for receiving the counter value is the same as the phase control circuit 113. Therefore, the phase control circuit 113A decreases the phase shift amount of the phase shifter 111 when the phase of the modulation signal vector is behind the phase of the input baseband signal, and conversely the phase of the modulation signal vector is If the phase of the input baseband signal vector is advanced, the phase shifter 11
A phase control signal PCb that increases the phase shift amount of 1 is generated.

Therefore, the negative feedback amplifier of FIG. 5 operates in the same manner as the embodiment of FIG. 1 except for the phase control circuit 113A, and similarly controls the phase shifter 111 in a feedback type.

The embodiment of FIG. 5 is similar to the modification of the embodiment of FIG. 1, and when the modulated signal vector crosses the I-axis or the Q-axis, the phase lag / lead determination is performed and the same as described above. The phase shifter control can be modified, and the phase lag / lead determination is performed every time the input baseband signal vector and the modulation signal vector cross the I axis or the Q axis to perform the phase shifter control. Of course, it can be done.

As described above, since the negative feedback amplifier of the present invention controls the phase shifter 111 in a feedback manner,
There is an advantage that the phase compensation accuracy can be increased successively and that there is no influence of signal delay on the phase difference detection.

The embodiment shown in FIG. 1 has a large signal level handled in the phase difference detection and therefore has a strong resistance to noise. The embodiment shown in FIG. 5 has a large phase difference between the detected signals and thus has a high phase detection sensitivity. There is.

[0045]

As described above, the present invention relates to the phase of the feedback baseband signal response vector, which is a combined vector of the baseband signals that respond to the first and second feedback baseband signals, by the phase control circuit. 1
And a phase control signal corresponding to the phase advance of the phase of the input baseband signal vector, which is a composite vector of the second input baseband signal, and the phase control signal shifts the phase of the carrier signal supplied to the quadrature demodulator. Since there is a transition to the phase shifter, there is an effect that the phase shift amount of the phase shifter can be stably and sequentially feedback-controlled, and the deterioration of the distortion improving characteristic of the negative feedback amplifier due to the phase rotation can be compensated.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of a negative feedback amplifier according to the present invention.

FIG. 2 is a vector diagram for explaining the first embodiment, in which (a) shows an input baseband signal vector and (b) shows a feedback baseband signal vector.

FIG. 3 is a block diagram of a phase control circuit 113 used in the first embodiment.

FIG. 4 is a signal waveform diagram of main signals in the phase control circuit 113.

FIG. 5 is a block diagram of a second embodiment of the negative feedback amplifier according to the present invention.

FIG. 6 is a block diagram of a negative feedback amplifier according to the related art.

7 is a block diagram of a circuit relating to the negative feedback amplifier of the present invention, (a) is a block diagram of a quadrature modulator, FIG.
(B) is a block diagram of the quadrature demodulator 112.

FIG. 8 is a vector diagram of signals relating to the negative feedback amplifier of the present invention, where (a) shows an input baseband signal and (b) shows a feedback baseband signal.

[Explanation of symbols]

 101,102 Terminals 103,104 Subtractor 105,106 Band limiting circuit 107 Oscillator 108 Quadrature modulator 109 Amplifier 110 Attenuator 111 Phase shifter 112 Quadrature demodulator 113,113A Phase control circuit 301 Phase difference detection circuit 302 Phase shifter 601 , 602, 603, 604 Terminals 605, 506, 607, 608 Limiter 609 Phase rotation determination circuit 610 Counter 611 Sine wave table 612 Cosine wave table 613, 614 D / A converter

Claims (5)

[Claims] 1. A first and second subtracted baseband signal, respectively, that subtracts the first and second feedback baseband signals from the first and second input baseband signals, respectively, to produce first and second subtracted baseband signals, respectively. A subtractor, first and second band limiting circuits that respectively band limit the first and second subtracted baseband signals to produce first and second modulated signals, and an oscillator produces a carrier signal,
A quadrature modulator that modulates the carrier signal with the first and second modulated signals to generate a quadrature modulated signal, an amplifier that amplifies the quadrature modulated signal, and a quadrature modulated signal from the carrier signal and the amplifier. Responsive to a portion of the quadrature modulated signal to demodulate the quadrature modulated signal to correspond to the first input baseband signal and the second feedback to correspond to the second input baseband signal. In a negative feedback amplifier including a quadrature demodulator that generates a baseband signal, a phase shifter that shifts the phase of the carrier signal supplied to the quadrature demodulator by a phase control signal, and the first and second feedback basebands. The first and second input bases with respect to the phase of the feedback baseband signal response vector, which is a composite vector of the baseband signals respectively responding to the signals. And a phase control circuit for generating the phase control signal corresponding to the phase advance of the input baseband signal vector which is a composite vector of the band signals. 2. A baseband signal responsive to each of the first and second feedback baseband signals is the first baseband signal.
And the second feedback baseband signal itself, and the phase control signal shifts the phase of the phase shifter when the phase of the vector of the feedback baseband signal lags behind the phase of the input baseband signal vector. The phase shift amount of the phase shifter is increased when the phase of the vector of the feedback baseband signal is advanced from the phase of the input baseband signal vector. Negative feedback amplifier. 3. A baseband signal responsive to each of the first and second feedback baseband signals is the first baseband signal.
And a second modulation signal, wherein the phase control signal increases the phase shift amount of the phase shifter when the phase of the vector of the modulation signal is delayed from the phase of the input baseband signal vector. The negative feedback amplifier according to claim 1, wherein the phase shift amount of the phase shifter is reduced when the phase of the vector of the modulation signal leads the phase of the input baseband signal vector. 4. The phase control circuit includes the input baseband signal and the first and second feedback bases which are not zero-crossed in the direction of zero-crossing at the zero-crossing instants of the first and second input base-band signals. In response to each polarity of the baseband signal of the band signal response, the phase control signal is generated by determining the lead or lag of the phase between the input baseband signal vector and the feedback baseband signal response vector. The negative feedback amplifier according to claim 1. 5. The phase control circuit receives the first and second input baseband signals and the baseband signal of the first and second feedback baseband signal responses and produces a polarity signal indicating the polarity thereof, respectively. A limiter and a direction of zero crossing at the instant when the polarity signals corresponding to the first and second input baseband signals cross zero crossing of the input baseband signal and the first and second feedback baseband signal responses that do not zero cross A phase rotation determination circuit that generates a phase lag advance signal indicating a phase lag between the input baseband signal vector and the feedback baseband signal response vector and a counter operation signal in response to a polarity signal of a baseband signal. , The count output is controlled according to the phase delay lead signal for each input of the counter operation signal. The negative feedback amplifier according to claim 4, further comprising a counter that counts up or counts down, and a phase shift amount setting circuit that generates the phase control signal corresponding to the count output.