JPH04288711A - Distortion compensating circuit for amplifier - Google Patents

Abstract

PURPOSE:To compensate the distortion of a high output amplifier having various distortion characteristics over a wide dynamic range by adjusting a bias to the driving electrode or the control electrode of a transistor used for an amplifier for generating distortion in the distortion compensating circuit.. CONSTITUTION:A variable voltage source is connected to a drain bias terminal 50 of the transistor used for an amplifier 20 for generating distortion in a distortion compensating circuit 10 so as to adjust a voltage Vd of the transistor. When the high output amplifier having satisfactory linearity is used as a high output amplifier 40 to compensate the distortion, the Vd of the amplifier 20 for generating distortion in the distortion compensating circuit 1O is increased and the distortion characteristic of the amplifier 20 for generating distortion is approximated to the distortion characteristic of the high output amplifier 40 so as to compensate the distortion over the wide dynamic range. When compensating the distortion of the high output amplifier 40 having defective linearity, the Vd of the amplifier 20 for generating distortion is decreased so as to compensate the distortion over the wide dynamic range.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distortion compensation circuit that compensates for signal distortion caused by nonlinearity of high-output amplifiers in high frequency bands including microwave and millimeter wave bands.

0002

2. Description of the Related Art FIG. 10 shows, for example,
1 is a configuration diagram showing a conventional high-output amplifier with a distortion compensation circuit disclosed in the publication. In the figure, 1 is an input terminal, 2 is an output terminal, 10 is a distortion compensation circuit, and 40 is a high output amplifier whose distortion is to be compensated. Furthermore, in the distortion compensation circuit 10, 12
is a divider that divides the signal input to input terminal 1 into three parts, 20
is a distortion generation amplifier, 21 and 22 are linear amplifiers, 25
a to 25e are variable attenuators; 30 is the distortion generation amplifier 2;
0 and the output of the linear amplifier 21 in opposite phase to extract distortion; 31 is the distortion extraction synthesizer 30;
This is a synthesizer that combines the distortion extracted in the above and the output of the linear amplifier 22 in opposite phase.

Next, the operation will be explained. The signal inputted to the input terminal 1 is introduced into the distortion compensation circuit 10, and then passed through the distributor 12.
It will be divided into 3 parts. The first distributed output of the distributor 12 is attenuated to a predetermined power by the variable attenuator 25a and then introduced into the distortion generating amplifier 20. The input power of the distortion generating amplifier is adjusted by a variable attenuator 25a. Distortion generation amplifier 20
The amplified signal containing distortion components is derived and introduced into the distortion extraction synthesizer 30 through the variable attenuator 25b. The second distributed output of the distributor 12 is introduced into the linear amplifier 21 through the variable attenuator 25c. The amount of attenuation of the variable attenuator 25c is set so that no distortion occurs when the signal is amplified by the linear amplifier 21. The distortion-free output of the linear amplifier 21 is introduced into the distortion extracting combiner 30, and is combined with the distortion-containing output of the distortion generating amplifier 20 in reverse phase. At this time, by setting the amount of attenuation of the variable attenuator 25b so that the amplitudes of the signals synthesized in opposite phases are equal, the signals are canceled and only the distortion generated by the distortion generating amplifier 20 is extracted. The distortion extracted by the distortion extraction synthesizer 30 is introduced into the synthesizer 31 through the variable attenuator 25d. Distributor 1
The third distributed output of 2 is amplified without distortion by the linear amplifier 22 through the variable attenuator 25e, and introduced into the combiner 31. Here, the amount of attenuation of the variable attenuator 25e is set so that no distortion occurs when the signal is amplified by the linear amplifier 22. A high output amplifier 40 is connected to the output of the synthesizer 31, that is, the output of the distortion compensation circuit 10.
1, the distortion extracted by the distortion extraction synthesizer 30 is transmitted to the variable attenuator 2 so as to cancel out the distortion generated by the high output amplifier 40.
The amplitude is adjusted at 5d and combined with the signal amplified by the linear amplifier 22. Therefore, only the signal component is output to the output terminal 2 of the high-power amplifier 40.

0004

[Problems to be Solved by the Invention] Since the conventional distortion compensation circuit of a high frequency amplifier is constructed as described above, the distortion characteristics with respect to the input power of the distortion generating amplifier in the distortion compensation circuit are as follows.
If the distortion characteristics of a high-power amplifier are not similar to the input power, it will not be possible to compensate for the distortion of a high-power amplifier over a wide input power range. There was a problem in that it was necessary to replace the amplifier with one with similar distortion characteristics.

The present invention was made to solve the above-mentioned problems, and it is possible to widely reduce the distortion of high-output amplifiers with different distortion characteristics without replacing the distortion generating amplifier in the distortion compensation circuit. The purpose of this invention is to obtain a distortion compensation circuit that can compensate over a dynamic range.

[0006]

[Means for Solving the Problems] A distortion compensation circuit for a high frequency amplifier according to the present invention is used in a distortion generation amplifier in the distortion compensation circuit according to the distortion characteristics with respect to the input power of the high output amplifier whose distortion is to be compensated. This makes it possible to adjust the bias applied to the drive electrode or control electrode of the transistor.

[0007]

[Operation] In the present invention, by adjusting the bias to the drive electrode or control electrode of the transistor used in the distortion generation amplifier in the distortion compensation circuit, the distortion characteristics with respect to the input power of the distortion generation amplifier are compensated for. Since the distortion characteristics can be made similar to the distortion characteristics of a high-output amplifier, it can be applied to multiple types of high-output amplifiers having different distortion characteristics without replacing the distortion generating amplifier.

[0008]

[Example] Example 1. FIG. 1 is a block diagram showing an embodiment of the present invention, where 1 is an input terminal, 2 is an output terminal, 10 is a distortion compensation circuit, and 40 is a high output amplifier whose distortion is to be compensated. In addition, the distortion compensation circuit 10
, 12 is a divider that divides the signal input to input terminal 1 into three parts, 20 is a distortion generation amplifier, 21 and 22 are linear amplifiers, 25a to 25e are variable attenuators, and 30 is the distortion generation amplifier 20 and the above. A distortion extraction combiner 31 combines the outputs of the linear amplifiers 21 in reverse phase and extracts distortion; 31 is a combiner that combines the distortion extracted by the distortion extraction combiner 30 and the output of the linear amplifier 22 in reverse phase; 50 is a distortion generation amplifier 2
A bias terminal 60 of the drain or collector of the transistor used in 0 is a variable voltage source connected to the bias terminal 50.

In the distortion compensation circuit configured as described above, a variable voltage source 60 is connected to the drain bias terminal 50 of the transistor used in the distortion generation amplifier 20 in the distortion compensation circuit 10. The structure is such that the drain voltage Vd of the transistor can be adjusted.

FIG. 2 shows an FET as a distortion generating amplifier 20.
This figure shows the dependence of the third-order intermodulation distortion IM3 on the input power Pin when an amplifier is used and the drain voltage Vd is set to 3V, 5V, and 7V. Note that third-order cross-modulation distortion is one type of distortion that occurs due to the nonlinearity of an amplifier when multiple signals of different frequencies are amplified simultaneously by an amplifier, and
When amplifying two signals of 1 and f2, 2f2 - f1
and 2f1 −f2 frequency components. Figure 2
In this case, the lower the Vd, the more distortion occurs at the lower Pin.

The high-output amplifier 40 for which distortion should be compensated is not limited to an amplifier with good linearity, but also an amplifier with good efficiency.
An amplifier with poor linearity may be used. Figure 3 shows an example of the output power Pout dependence of IM3 of an amplifier with good linearity, and Figure 4 shows an example of the Pout dependence of IM3 of an amplifier with poor linearity.
This shows an example of out dependence. When the output power is lowered, the distortion of an amplifier with good linearity decreases rapidly as shown in FIG. 3, but the distortion of an amplifier with poor linearity does not decrease much as shown in FIG. 4.

FIG. 5 shows the results of distortion compensation performed using a high output amplifier 40 with good linearity and the distortion characteristics shown in FIG. 3 as the high output amplifier 40 whose distortion is to be compensated. If Vd of the distortion generation amplifier 20 in the distortion compensation circuit 10 is set to 7V, distortion can be compensated over a wide dynamic range.
is 3V, the distortion compensation circuit 1 in the low output power region
0, distortion occurs, but in the high output amplifier 40, almost no distortion occurs, so the distortion is increased by the distortion compensation circuit 10. Therefore, when performing distortion compensation for a high-output amplifier with good linearity, the Vd of the distortion generation amplifier 20 of the distortion compensation circuit 10 is increased, and the distortion characteristics of the distortion generation amplifier 20 and the distortion characteristics of the high-output amplifier are increased. By approximating , distortion can be compensated over a wide dynamic range.

FIG. 6 shows the results of distortion compensation performed using a high output amplifier 40 with good linearity and the distortion characteristics shown in FIG. 4 as the high output amplifier 40 whose distortion is to be compensated. If Vd of the distortion generation amplifier 20 in the distortion compensation circuit 10 is set to 3V, distortion can be compensated over a wide dynamic range.
is 7V, the distortion compensation circuit 1 in the low output power region
0, no distortion occurs, but the high output amplifier 40 produces distortion, so the distortion is not reduced by the distortion compensation circuit 10. Therefore, when performing distortion compensation for a high-output amplifier with poor linearity, the voltage of the distortion generation amplifier 20 of the distortion compensation circuit 10 is
By lowering d and approximating the distortion characteristics of the distortion generating amplifier 20 and the distortion characteristics of a high-output amplifier, it is possible to compensate for distortion over a wide dynamic range.

As described above, in order to compensate for distortion over a wide dynamic range, the distortion characteristics of the high-output amplifier 40 that should be compensated for distortion and the distortion characteristics of the distortion generating amplifier 20 in the distortion compensation circuit 10 are similar to each other. Must be.

For example, for an amplifier with good linearity such as a solid state high output amplifier, Vd of the FET amplifier may be set to a high voltage of 5 V or more, and for an amplifier with good linearity such as a traveling wave tube amplifier For such defective amplifiers, Vd may be set to a low voltage of 5V or less.

Example 2. In the first embodiment, only the Vd of the distortion generating amplifier 20 is changed, but if the passing phase of the amplifier changes due to Vd, the Vd of the linear amplifier 21 is also changed at the same time. The phase relationship is maintained when the output of the distortion generating amplifier 20 and the output of the linear amplifier 21 are combined.

Example 3. In the second embodiment, considering the change in the passing phase due to the Vd of the amplifier, the linear amplifier 21
The Vd of the distortion generating amplifier 20 was made common to the Vd of the distortion generating amplifier 20, but focusing on the fact that the synthesizer 31 synthesizes the distortion extracted by the distortion extracting synthesizer 30 and the output of the linear amplifier 22 in opposite phase, the linear amplifier The Vd of the distortion generating amplifier 22 may also be made common to the Vd of the distortion generating amplifier 20.

Example 4. In the first to third embodiments described above, the distortion characteristics with respect to the pin of the distortion generating amplifier 20 are changed by Vd, but the distortion characteristics may be controlled by the gate voltage Vg instead of Vd. FIG. 7 shows V corresponding to the third embodiment above.
FIG. 7 shows a configuration diagram of a distortion compensation circuit having adjustment means according to g. In the figure, 51 is a gate or base bias terminal.

FIG. 8 shows the IM3 characteristic with respect to Pin when the Vg of the FET amplifier is set so that the amplifier operates as class A, class AB, or class B. Instead of Vd,
Distortion characteristics can be controlled by Vg.

Example 5. In the fourth embodiment, the distortion characteristics are changed only by Vg, but the distortion characteristics may be changed by both Vd and Vg.

Example 6. In Examples 1 to 5 above,
Although the circuit configuration consisting of one distortion generating amplifier and two linear amplifiers has been described, similar effects can be achieved with other circuit configurations.

FIG. 9 shows an example adapted to a distortion compensation circuit having another circuit configuration. In the figure, 11a is the input terminal 1.
A divider 11b divides the input signal into two parts, and a divider 11b divides the signal amplified by the linear amplifier 21 into a distortion extraction combiner 30 and a combiner 3.
This is a distributor that divides 1 into 2. In this case, the same effect can be achieved by changing the Vd of one distortion generating amplifier 20 and one linear amplifier 21.

[0023]

As described above, according to the present invention, by adjusting the bias to the drive electrode or the control electrode of the transistor used in the distortion generating amplifier in the distortion compensation circuit, amplifiers with different distortion characteristics can be adjusted. This has the advantage that distortion compensation can be performed over a wide dynamic range.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a distortion compensation circuit according to a first embodiment of the present invention.

FIG. 2 shows distortion characteristics using the drain voltage of the distortion generating amplifier used in Example 1 of the present invention as a parameter.

FIG. 3 shows distortion characteristics of a high-output amplifier with good linearity and which is compensated for distortion according to the first embodiment of the present invention.

FIG. 4 shows distortion characteristics of a high-power amplifier with poor linearity whose distortion is compensated for according to the first embodiment of the present invention.

FIG. 5 shows distortion characteristics of the high-output amplifier shown in FIG. 3 when distortion compensation is performed using the distortion compensation circuit according to the first embodiment of the present invention.

FIG. 6 shows distortion characteristics of the high-output amplifier shown in FIG. 4 when distortion compensation is performed using the distortion compensation circuit according to the first embodiment of the present invention.

FIG. 7 is a configuration diagram of a distortion compensation circuit according to a fourth embodiment of the present invention.

FIG. 8 shows distortion characteristics using the gate voltage as a parameter of the distortion generating amplifier according to the fourth embodiment of the present invention.

FIG. 9 is a configuration diagram of a distortion compensation circuit according to a sixth embodiment of the present invention.

FIG. 10 is a configuration diagram of a conventional distortion compensation circuit.

[Explanation of symbols]

1 Input terminal 2 Output terminal 10 Distortion compensation circuit 11a, 11b Distributor 12 3-distributor 20 Distortion generation amplifiers 21, 22 Linear amplifiers 25a to 25e Variable attenuator 30 Distortion extraction combiner 31 Combiner 40 Distortion should be compensated High output amplifier 50 Drain or collector bias terminal 51
Gate or base bias terminal 60 Variable voltage source

Claims (1)

[Claims] Claim 1: In a circuit that has a distortion generation amplifier and uses distortion components generated by the amplifier to compensate for distortion generated in the amplifier, the distortion Distortion compensation for an amplifier, characterized in that means is provided for adjusting the distortion characteristics of the distortion generation amplifier with respect to input power, and the adjustment is performed by biasing a drive electrode or a control electrode of a transistor used in the distortion generation amplifier. circuit.