JPS61121607A - Feedforward amplifier - Google Patents

Abstract

PURPOSE:To suppress the increase in gain fluctuation and distortion level of an amplifier caused by temperature and power characteristics by adjusting automatically the gain depending on the difference of the absolute value of the transmitted quantity of between a pilot signal component fed to an error amplifier via a main amplifier and a pilot signal component fed to the error amplifier via a delay circuit. CONSTITUTION:A hybrid circuit 10 extracting a part of an output signal of a main amplifier 2 of an error detection loop and a hybrid circuit 11 extracting a part of an output signal of a delay line 3 are provided, a signal obtained from both the hybrid circuits is given to control circuits 12, 13, the pilot signal component included in the amplified signal, given to an operational amplifier 14 as a DC current to extract the difference of the absolute value of the pilot signal transmission quantity of loops (a, b), and the attenuation of an automatic equalizer 15 provided in the loop (b) or the gain of a main amplifier 2 of the loop (a) is adjusted automatically so as to compress the difference. Thus, when both the signals is inputted to an error amplifier 7, the signal component is cancelled completely mutually and only the error component generated from the main amplifier is fed to the error amplifier.

Description

DETAILED DESCRIPTION OF THE INVENTION Utilization field on C1tili] The present invention relates to an improved method for suppressing errors in a feedforward multiplier.

The feedforward amplifier adds the main amplified six human power signals to the main amplifier output signal with a phase difference of 180° and the same absolute value, extracts only the error (distortion, etc.) component of the main amplifier as the addition result, and then adds this signal to the main amplifier output signal. After the error component is amplified, it is added again to the output signal of the main amplifier with a phase difference of 180°, thereby obtaining a signal free of error components as the output signal of the feedforward amplifier.

In other words, it is possible to completely suppress the error cup of the main amplifier and generate an error-free output signal at the output of the 7-doforward amplifier. [Prior Art] The operation of the feedforward amplifier is shown in FIG. A conventional example will be explained.

FIG. 2 is a block diagram of the entire amplifier, which includes an error detection loop having the loops ① and 0 shown in the figure, and an error injection detection loop consisting of the loops ① and ＠. An input signal is applied from an input terminal IN and is divided into two by a hybrid circuit 1 to a main amplifier 2 and a delay line 3. It is amplified by the main amplifier l.

A part of the input signal branched at the hybrid circuit 1 reaches the hybrid circuit 6 via the delay line 3.

These two signal paths are shown in FIG. 2 as loops 1 and 2. When these two signals are inputted from the hybrid circuit 6 to the error amplifier 7, the conditions for the error detection loop are that the absolute values of mutual transmission amounts are equal and the phases are reversed by 180°.

The absolute value of the transmission amount is adjusted by the amount of attenuation of the attenuator 5, and the phase is adjusted by selecting the delay # and t of the delay line 3.

In this case, the only human input to the error amplifier 7 is the Lano error distortion signal from the main amplifier 2, which is amplified by the error amplifier 7.

The output of the main amplifier 2 passes through the delay line 8 and reaches the output terminal OUT via the loop (2), and the error signal amplified by the error amplifier 7 arrives at the output terminal OUT via the loop (2).

② By inverting the phase relationship by 180' to equalize the absolute value of the transmission amount of the fD loop, the output terminal OUT
At this point, the error component in the main signal that has arrived at OUT via the QI loop, that is, the main amplifier output signal, is transmitted to the error amplifier 7.
This can be completely canceled by the opposite phase error signal supplied from the output section of the OUT terminal, and a signal output free of error components is obtained from the OUT terminal.

[Problem that the invention seeks to solve]

However, it is difficult to maintain the characteristics of the error detection loop circuit of the feedforward amplifier constant, and changes therein adversely affect the transmission characteristics from the input of the amplifier to the cutting terminal.

For example, if the ambient temperature is subject to a large change, the amount of transmission between the input section IN of the amplifier and the input point of the error amplifier 7 will change. If the change occurs, the transmission characteristics of ■Loop■Loop change, and the absolute value of the signal component becomes a different value, and the signal component leaks to the error amplifier 7, and the error injector 1 loop transfers the error component. Not only is it impossible to cancel, but
A signal distorted by the leakage signal provided from the error amplifier 7 is sent out from the OUT terminal.

[Means for solving problems]

The problem mentioned above is that the pilot signal component supplied to the error amplifier via the main amplifier and the pilot signal component supplied to the error amplifier via the delay circuit are detected independently, and the absolute value of the amount of transmission of both pilot signals is determined. make a difference,
This problem is solved by the feedforward amplifier according to the present invention, which has the feature of automatically adjusting the attenuation of an automatic isolator provided in the loop including the delay circuit or the gain of the main amplifier using the difference signal.

[For production]

According to the present invention, the signal obtained through the main amplifier in the error detection loop and the signal given an inverted phase of 1800 through the delay circuit are adjusted so that their absolute values are equal by gain control using the pilot signal. Ru.

Therefore, when both signals are input to the error amplifier, the signal components completely cancel each other out, and only the error component generated from the main amplifier is fed to the error amplifier.
In the next error injection loop, the error components contained in the output signal of the main amplifier can be completely canceled, and only correct signal components without error components are obtained from the output of the feedforward amplifier.

〔Example〕

The gist of the present invention will be explained in detail below with reference to the embodiment shown in FIG.

The figure is a block circuit diagram of a feedforward amplifier,
The same parts as in FIG. 2 are indicated by the same symbols.

According to the present invention, a hybrid circuit 10 that takes out a part of the output signal of the main amplifier 2 of the error detection loop of a conventional feedforward amplifier and a hybrid circuit 11 that takes out a part of the output signal of the delay line 3 are provided. The signals obtained from the circuits are supplied to control circuits 12 and 13, respectively, and the control circuits R-wave rectify the pilot signal component included in the amplified signal and provide it as a direct current to the operational amplifier l4, which connects the loop and The difference in the absolute value of the pilot signal transmission amount of the loop is extracted, and the attenuation of the automatic equalizer 15 provided in the loop or the gain of the main amplifier 2 of the loop is automatically adjusted so that this difference can be compressed. Configure. Note that the pilot signal is inserted before the input section of the feedforward amplifier.

According to the present invention, two signal components which are to be mutually canceled in the error detection loop and which are applied to the error amplifier 7 through the loop (1) and (4) are detected by replacing the difference in their absolute values with the pilot level difference, The amount of attenuation in the error detection loop is adjusted so that the level difference is reduced, and the amount of suppression of the signal component in the error detection loop is increased.

〔Effect of the invention〕

As described above, according to the present invention, the temperature characteristics of the main amplifier,
Gain fluctuations in the feedforward amplifier due to power supply characteristics and increases in the distortion level of the error amplifier can be suppressed, and even when feedforward amplifiers are connected in multiple stages, the circuit can be easily configured with just one pilot generator. Although the structure is simple, its effects are great.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram showing an embodiment of a feedforward amplifier according to the present invention, and FIG. 2 is a block circuit diagram of a conventional feedforward amplifier. In the figure, 1.4.6, 9, 10.11 are the hybrid circuit 2, the main amplifier 3.8, the delay line 5, the attenuator 7, the error amplifier 12.13, the control circuit 14, the operational amplifier Loop circuit belonging to the error detection loop ■@ indicates a loop circuit belonging to the error injection ■y loop.

Claims (1)

[Claims] Detecting independently the pilot signal component supplied to the error amplifier via the main amplifier and the pilot signal component supplied to the error amplifier via the delay circuit, and creating a difference in the absolute value of the transmission amount of both pilot signal components, A feedforward amplifier characterized in that the attenuation of an automatic equalizer provided in a loop including a delay circuit or the gain of a main amplifier is automatically adjusted by the difference signal.