JPH10150327A - Amplifier circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce distortion in an amplified output of an amplifier that amplifies a broad band digital modulation wave. SOLUTION: An amplified output of an amplifier 1 is detected by a directional coupler 2. The detected signal passes through a band pass filter 3 to execute an extraction of an adjacent channel leaked part. Then a detector 4 detects the amount of the extracted adjacent channel leak and supplies the result to a control circuit 5 as a control signal. The control circuit 5 controls a bias of the amplifier 1 by using the detected signal so that the adjacent channel leakage amount of the amplified output is less than the value specified by the system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an amplifier circuit used for wideband digital modulation.

[0002]

2. Description of the Related Art Conventionally, when class A amplification is performed in an amplifier,
Since the linearity of the input / output characteristics is very good, it has been used as a low distortion amplifier. However, the class A amplifier has a disadvantage that power efficiency is poor. In addition, efficient AB
In a class amplifier, distortion occurs in the amplified output. In the distortion, the input signal is not proportional to the distortion component, and the distortion may be increased at a low level. Conventionally, in order to prevent this, the input signal is detected and the amplifier bias is changed, so that the operating point is set to A
By switching to a level close to the class, the increase in distortion was prevented.

[0003]

However, an amplifier used for wideband digital modulation has a problem of adjacent channel leakage power due to distortion of a pulse modulation output. Conventional level bias control is not sufficient.

An object of the present invention is to provide a low distortion amplifier circuit which can amplify an input wave with low distortion and more faithfully when amplifying the wideband digital modulation wave.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to provide a detector for detecting an output signal of an amplifier, a band-pass filter for extracting an adjacent channel leak portion from the detected signal, and detecting the extracted adjacent channel leak amount. And a control circuit that variably controls the bias of the amplifier so that the adjacent channel leakage amount falls below a specified value at the detection output.

It is another object of the present invention to provide a detector for detecting an output signal of an amplifier, a frequency converter for performing frequency conversion by using a carrier wave of the detection signal and a local oscillation signal, and an adjacent channel leakage portion from the converted intermediate frequency signal. And a control circuit for variably controlling the bias of the amplifier so that the adjacent channel leakage amount is reduced to a specified value or less at the detection output. Is achieved by

[0007] According to the above means, the adjacent channel leakage portion can be extracted from the output signal of the amplifier by the band pass filter. By variably controlling the bias of the amplifier according to the adjacent channel leakage amount, the adjacent channel leakage amount of the amplifier output can be reduced to a specified value or less, and the distortion can be controlled to be small.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, wherein 1 is an amplifier for amplifying a wideband digital modulation wave, and the output of the amplifier is detected by a detector 2 such as a directional coupler. The detection signal passes through a band-pass filter 3 to extract an adjacent channel leakage power portion. Next, the extracted adjacent channel leakage amount is detected by the detector 4 to obtain a signal for control. The control circuit 5 controls the bias of the amplifier 1 to change the operating point. That is, the bias is changed and controlled by the signal from the detector 4 so that the adjacent channel leakage amount of the output of the amplifier 1 becomes equal to or less than the minimum value specified by the system.

A spectrum waveform due to distortion can be inferred in advance by the modulation rate, band limitation, modulation method, and the like of the amplified signal input to the amplifier 1. FIG. 2 shows the spectrum of the modulated wave output. Side lobes spread on both sides of the main lobe, and this is adjacent channel leakage power.

For this reason, the band-pass filter 3 determines the center frequency and the bandwidth from the spectrum waveform to the band-pass characteristics through which the leakage power portion of the side lobe passes. Thereby, the determined band-pass filter 3
The control circuit 5 can detect the adjacent channel leakage amount from the detection value obtained by
Controls the bias of the amplifier 1.

When amplifying a broadband digital modulation wave, the side lobe of the spectrum spreads to the amplified output due to the non-linearity of the amplifier 1, as shown in FIG.
In a class AB amplifier, the non-linearity changes depending on the operating point, so that the operating point is changed based on the amount of leakage detected, so that the adjacent channel leakage portion due to the side lobe can be reduced, and the distortion is reduced. be able to.

FIG. 3 shows another embodiment of the present invention. This is performed by converting the distortion to an intermediate frequency and detecting the distortion in a narrow band. The frequency of the detection signal detected by the directional coupler 2 is converted by the frequency converter 6. The local oscillator 7 supplies a local oscillator signal (Lo) as a carrier to the frequency converter 6, and converts the frequency of the detection signal from the directional coupler 2. The adjacent channel leakage portion is selected by the band pass filter 3 from the intermediate frequency signal converted into the difference between the two frequencies, and is detected by the detector 4. The detection signal is supplied to the control circuit 5 to control the bias of the amplifier 1 and to control the adjacent channel leakage amount to be small and to be equal to or less than a specified value. By converting the signal into an intermediate frequency signal and detecting the signal, the adjacent channel leakage amount can be extracted in a narrow band, so that the optimum bias control of the amplifier 1 can be performed.

In another embodiment, the local oscillator signal (Lo) of the local oscillator 7 shown in FIG. 3 is swept over a certain range (the whole or a part of the adjacent channel) and added to the frequency converter 6 to add the adjacent channel leakage power. Is integrated and extracted. Thus, optimal control can be performed by controlling the bias of the amplifier based on the integrated and extracted signal.

[0015]

As described above, according to the present invention, it is possible to control the amplifier so that the amount of adjacent channel leakage is reduced to a value less than the value specified by the system while making a trade-off with the current consumption. This has the effect of optimizing both.

[Brief description of the drawings]

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

FIG. 2 is a spectrum of an amplifier output.

FIG. 3 is a block diagram of another embodiment of the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 amplifier, 2 directional coupler, 3 bandpass filter, 4 detector, 5 control circuit, 6 frequency converter, 7
... local oscillator.

Claims (2)

[Claims] 1. An amplifier circuit for amplifying a wideband digital modulation wave, a detector for detecting an output signal of the amplifier, a band-pass filter for extracting an adjacent channel leak portion from the detected signal, and an extracted adjacent channel leak signal An amplifier circuit, comprising: a detector for detecting an amount of the signal; and a control circuit for variably controlling a bias of the amplifier so that an adjacent channel leakage amount is reduced to a specified value or less at the detection output. 2. An amplifying circuit for amplifying a wideband digital modulation wave, a detector for detecting an output signal of the amplifier, a frequency converter for performing frequency conversion of the detection signal by a carrier wave of a local oscillation signal, and A band-pass filter for extracting an adjacent channel leakage portion from the intermediate frequency signal, a detector for detecting the extracted adjacent channel leakage amount, and a bias of the amplifier so that the adjacent channel leakage amount is reduced to a specified value or less at the detection output. And a control circuit for variably controlling the power supply.