JPH0794954A - Power amplifier device - Google Patents

Abstract

PURPOSE:To provide a power amplifier device capable of surely compensating distortion even in the vicinity of a saturated output level over a wide output level range of the output level by simple circuit constitution. CONSTITUTION:The power amplifier device is constituted of a power amplifier 2 for amplifying an input signal, a distributer 3 for branching a part of a signal outputted from the amplifier 2, a variable phase shifter 5 for adjusting the phase of the signal branched by the ditributer 3 so as to reverse the phase, a variable attenuator 6 for adjusting the level of a distortion component in the branched signal to the same level as that of a distortion component generated from the amplifier 2, and a synthesizer 1 for synthesizing the branch signal adjusted with its phase and level with the input signal to the amplifier 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power amplifier used in a microwave transmitting / receiving device such as a telephone or a television.

[0002]

2. Description of the Related Art In a power amplifier used in a microwave transmitter / receiver, when the level of an input signal is increased, second-order, third-order, fourth-order, and higher-order distortions of a transmission / reception frequency are generated, so that an operating point is increased. If it is lowered and used in a place where distortion is small, efficiency will decrease. Therefore, in a conventional power amplifier, a distortion generating circuit is used to compensate for this distortion.

FIG. 2 shows a conventional power amplifying device using a distortion generating circuit. As shown in FIG. 2, the distortion generating circuit 11 is connected to the preceding stage of the power amplifier 12 and generates an inverse distortion signal having the same level as the distortion component generated by the power amplifier 12 but having an opposite phase. This inverse distortion signal cancels the distortion component generated in the power amplifier 12 to perform distortion compensation.

FIG. 3 shows an example of a conventional distortion generating circuit 11.

The input signal input to the input terminal A is divided into a distortion route and a signal route by the distributor 13, the distortion route is further distributed by the distributor 14, and one signal is distorted by the distortion generator 15. Generate a signal. The other signal is passed through the variable phase shifter 16 and the variable attenuator 17 and then to the combiner 1
At 8, it is combined with the distortion signal. At this time, the variable phase shifter 16 and the variable attenuator 17 are set so that the signals are canceled by the combiner 18, and the combiner 18 outputs only the distortion component. The distortion component is further variable phase shifter 1
After passing through 9 and the variable attenuator 20, the phase of the distortion component is adjusted by the variable phase shifter 19, the amplitude is adjusted by the variable attenuator 20, and combined with the signal of the signal route in the combiner 21. In this way, the level of the distortion component output from the combiner 18 is adjusted to the level of the distortion component generated by the power amplifier 12, and the phase is set to the opposite phase to cancel the distortion component of the signal output from the power amplifier 12. You can

[0006]

However, in the conventional distortion compensation using the distortion generation circuit, it is difficult to compensate the distortion over a wide range of the output level of the power amplifier.
In particular, high-order distortion occurs near the saturated output level of the power amplifier, and especially odd-order distortion becomes a problem, but it is not possible to compensate all high-order distortion with a single distortion generation circuit as in the past. It is possible. Therefore, a method of providing a distortion generation circuit for each of the secondary, tertiary, and quaternary distortions and synthesizing the signals after distortion removal may be adopted, but this would complicate the circuit configuration and also reflected in the cost. However, the distortion cannot be completely removed.

The present invention has been made in view of the above points, and an object of the present invention is to provide a power amplifying device capable of surely compensating for distortion over a wide range of output levels with a simple circuit configuration, particularly near the saturated output level. .

[0008]

In order to achieve the above object, the present invention provides a distributor for branching a part of a signal output from a power amplifier for amplifying an input signal, and a signal branched by the distributor. And a variable attenuator that adjusts the level of the distortion component of the branched signal to the same level as the level of the distortion component generated in the power amplifier. , And a combiner for combining the phase adjusted and level adjusted branch signal with the input signal to the power amplifier.

[0009]

With the above structure, a part of the output signal from the power amplifier is branched by the distributor, the branched signal is made to have an opposite phase by the variable phase shifter, and the level of the distortion component is changed through the variable attenuator. The distortion of the power amplifier is canceled by equalizing the level of the distortion signal generated in 1) and then combining the input signal with a combiner provided on the input side of the power amplifier.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a power amplifier device as an embodiment of the present invention.

With respect to the power amplifier 2, a combiner 1, a distributor 3, a filter 4, a variable phase shifter 5, and a variable attenuator 6 are provided.
Are connected as shown in the drawing, a part of the signal output from the power amplifier 2 is branched by the distributor 3, and the branched signal is passed through the filter 4, the variable phase shifter 5 and the variable attenuator 6 to the input side of the power amplifier 2. The provided combiner 1 combines the input signal.

The signal branched by the distributor 3 contains distortion generated in the power amplifier 2 in addition to the original signal. By adjusting the variable phase shifter 5 and the variable attenuator 6 to set the distortion of the branch signal to the opposite phase and the same level as the distortion signal generated in the power amplifier 2, the distortion signal is output at the output of the power amplifier at the output terminal B. Is canceled. In this case, the degree of attenuation by the variable attenuator 6 is determined in consideration of the degree of distortion compensation and the original degree of signal attenuation.

In the high frequency band, the internal and external phases of the band differ depending on the electrical length of the circuit for returning the branched signal to the input side. Therefore, when distortion compensation is performed with the target signal band in the opposite phase, the output signal from the power amplifier and the feedback signal may be in phase and oscillate outside the band. In order to prevent such a situation, a filter 4 is inserted in the feedback circuit so that it is attenuated except the required band so that positive feedback is not obtained.

In the present invention, the signal used for distortion compensation is a signal branched from the signal generated in the power amplifier 2 itself, so that distortion compensation can be performed even for higher-order distortion generated near the saturated output level.

[0016]

As described above, according to the present invention,
Since the distortion component of the signal branched from the output of the power amplifier is used for the distortion compensation, there is an effect that high-order distortion near the saturation output level of the power amplifier can be surely canceled.

[Brief description of drawings]

FIG. 1 is a block diagram of a power amplification device that is an embodiment of the present invention.

FIG. 2 is a block diagram of an example of a conventional power amplification device.

3 is an example of a distortion generation circuit used in the power amplification device shown in FIG.

[Explanation of symbols]

 1 Combiner 2 Power Amplifier 3 Divider 4 Filter 5 Variable Phaser 6 Variable Attenuator

Claims (2)

[Claims] 1. A power amplifier for amplifying an input signal, and a distributor for branching a part of a signal output from the power amplifier,
A variable phase shifter that adjusts the phase of the signal branched by the distributor so that the phase is reversed, and the level of the distortion component of the branched signal is set to the same level as the level of the distortion component generated by the power amplifier. A power amplifying device comprising: a variable attenuator that adjusts the level so as to achieve the above; and a combiner that combines the phase-adjusted and level-adjusted branch signal with the input signal. 2. The power amplification device according to claim 1, further comprising a filter that limits a band of the branch signal.