JPH05235648A - Phase compensation circuit for power amplifier - Google Patents

Abstract

PURPOSE:To improve the C/N by detecting a power supply voltage fed to a power amplifier and controlling the amplitude of an envelope detection output signal in response to its detection output so as to compensate a change in phase distortion due to power supply voltage fluctuation. CONSTITUTION:A differential amplifier circuit 7 compares a signal resulting from envelope detection of a modulated carrier with less amplitude distortion inputted from an input terminal 1 at an envelope detection circuit 6 with a signal resulting from envelope detection of a modulated carrier having amplitude distortion from a power amplifier 4 at an envelope detection circuit 8. Since an AGC circuit 2 is controlled by the signal difference, the amplitude distortion is improved. Furthermore, an output of a power supply voltage detection circuit 11 is given to an AGC circuit 10, in which an amplitude of a signal subject to envelop detection is changed corresponding to the power supply voltage. Thus, phase distortion generated by the power amplifier is reduced to suppress the deterioration in the C/N.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase compensating circuit for a linear power amplifier such as a .pi. / 4 shift QPSK radio device.

[0002]

2. Description of the Related Art As a conventional technique, for example, Japanese Patent Application No. 3-7.
There is a power amplifier phase compensation circuit such as that shown in 6970. FIG. 2 shows a block diagram of a power amplifying section of a π / 4 shift QPSK radio apparatus shown in this conventional example. The modulated carrier wave input from the input terminal 1 is AGC
After passing through the circuit 2 and the phase modulation circuit 3, it is amplified by the power amplifier 4 supplied with the power supply voltage 9 and output to the output terminal 5. On the other hand, a part of the modulated carrier wave from the input terminal 1 is subjected to envelope detection by the envelope detection circuit 6 and then given to the first input terminal of the differential amplifier circuit 7. A part of the output of the power amplifier 4 is subjected to envelope detection by the envelope detection circuit 8 and then given to the second input terminal of the differential amplification circuit 7. The differential amplifier circuit 7 amplifies the difference between the two input signals and controls the AGC circuit 2.

Next, this operation will be described. Generally, the power amplification section becomes non-linear as shown in the amplitude input / output characteristic of FIG. The differential amplifier 7 envelope-detects the modulated carrier wave with less amplitude distortion input from the input terminal 1 by the envelope detection circuit 6 and the modulated carrier wave with amplitude distortion generated by the power amplifier 4. Amplitude distortion is improved because the signal detected by the envelope detection in the circuit 8 is compared and the AGC circuit 2 is controlled by the signal of the difference.

Further, a part of the output of the envelope detection circuit 6 obtained by envelope-detecting the input modulated carrier wave is input to the phase modulation circuit 3 and the phase modulation having the reverse tendency characteristic of the phase input / output characteristic of the power amplifier 4 is performed. To the modulated carrier wave to compensate for the phase distortion of the power amplifier 4.

However, in the conventional technique, although the amplitude distortion and the phase distortion are compensated as described above, the phase input / output characteristic of the power amplifier depends on the power supply voltage as shown in FIG.
Phase distortion compensation deviates from the optimum value due to power supply voltage fluctuation C /
There was a drawback that N deteriorated.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in order to eliminate the above-mentioned drawbacks of the prior art, and compensates the change in the phase distortion generated in the power amplifier due to the power supply voltage and improves the C / N. The purpose is to provide a circuit.

[0007]

In order to achieve the above object, the present invention changes the amplitude of an envelope detection signal input to a phase modulation circuit by a signal whose power supply voltage is detected, and then phase-shifts the modulated carrier wave. It is designed to apply modulation.

[0008]

As a result, the phase distortion generated in the power amplifier is reduced and the C / N is improved.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIG. The modulated carrier wave input from the input terminal 1 is AG
After being subjected to phase modulation by the phase modulation circuit 3 via the C circuit 2, it is amplified by the power amplifier 4 and given to the output terminal 5. On the other hand, a part of the modulated carrier wave from the input terminal 1 is subjected to envelope detection by the envelope detection circuit 6, and its output is AGC.
The signal is supplied to the circuit 10 and is also supplied to the first input terminal of the differential amplifier circuit 7.

A part of the output of the power amplification circuit 4 is envelope-detected by the envelope detection circuit 8 and then given to the second input terminal of the differential amplification circuit 7. Differential amplifier circuit 7
Is an AGC circuit 2 that amplifies the difference between the two input signals and
To control. Further, the power supply voltage detection circuit 11 detects the power supply voltage supplied from the power supply input terminal 9 and controls the gain of the AGC circuit 10 by this power supply voltage.

Next, this operation will be described. The differential amplifier circuit 7 has a signal obtained by performing envelope detection on the modulated carrier wave with less amplitude distortion input from the input terminal 1 by the envelope detection circuit 6,
The modulated carrier wave in which the amplitude distortion is generated in the power amplifier 4 is compared with the signal subjected to the envelope detection in the envelope detection circuit 8, and the AGC circuit 2 is controlled by the signal of the difference, so that the amplitude distortion is improved.

The output of the power supply voltage detection circuit 11 is AG
Since the amplitude of the envelope-detected signal given to the C circuit 10 is changed in accordance with the power supply voltage, it is possible to reduce the phase distortion generated in the power amplifier and suppress the deterioration of C / N.

[0013]

As described above, according to the present invention, it is possible to realize a phase compensation circuit with improved C / N by compensating for the phase distortion generated in the power amplifier due to the fluctuation of the power supply voltage.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional example.

FIG. 3 is an input / output amplitude characteristic of a power amplifier.

FIG. 4 is an input / output phase characteristic of a power amplifier.

[Explanation of reference numerals] 1 input terminal 2 AGC circuit 3 phase modulation circuit 4 power amplifier 5 output terminal 6 envelope detection circuit 7 differential amplifier 8 envelope detection circuit 9 power supply voltage terminal 10 AGC circuit 11 power supply voltage detection circuit

Claims (1)

[Claims] 1. A power amplifier, means for envelope detection of a modulated carrier wave input to the power amplifier, and means for applying phase modulation to the modulated carrier wave according to the envelope detection output signal. In the phase compensation circuit of the power amplifier, means for detecting the power supply voltage supplied to the power amplifier and means for controlling the amplitude of the envelope detection output signal according to the power supply voltage detection output are provided. And a power amplifier phase compensation circuit.