JPH0435084B2 - - Google Patents

Abstract

PURPOSE:To curtail the man-hour for an adjustment by providing a distortion level adjusting means for adjusting a level of a compensating distortion, on the previous stage of a branching means. CONSTITUTION:When a level of an input signal is varied, a tertiary distortion component is varied by three times of a level variation quantity of the input signal, therefore, a level of a tertiary distortion component of an output side of a synthesizing means 12 can be controlled by a distortion level adjusting means 14 which has been provided in front of a branching means 9. Due to before branching, a temperature characteristic of this distortion level adjusting means 14 exerts an influence in the same way on both parts which have been made to branch, therefore, no influence is exerted on the output side of the synthesizing means 12. Therefore, by this distortion level adjusting means 14, a distortion level is adjusted in a state that an isolation is good, by using a circulator, and also, a semi-fixed attenuator is inserted into a distortion generation amplifying means 11 so that the attenuation quantity is not varied, by which the generation of a phase shift is prevented. In this way, the man-hour for an adjustment can be curtailed by eliminating a readjustment.

Description

[Detailed Description of the Invention] [Summary] In a distortion compensator, the level of an input microwave is adjusted by a distortion level adjusting means sandwiched between circulators, and then branched and shifted by a phase shifting means, and a distortion generating amplification device. This is intended to reduce the number of adjustment steps by synthesizing the distortion generated by amplifying the distortion generated by the compensation amplifier to generate compensation distortion having an opposite phase and equal amplitude to the distortion generated by the compensated amplifier.

[Industrial application field]

The present invention relates to improvements in distortion compensators used in microwave bands, for example.

In recent years, in digital communications using microwaves, for example, 16-value orthogonal amplitude modulation has been put into practical use in order to make effective use of frequencies, but there is a trend toward multi-value modulation, such as 256 values, to further improve usage efficiency. .

Since this modulation method changes the amplitude and phase of the carrier wave in accordance with the modulation signal, the power amplifier used for this method must amplify changes in amplitude and phase without distortion, so it operates in class A. Moreover, the maximum output level is higher than the standard output level, e.g.
Since it has to be increased by more than 10 dB, power consumption increases.

Therefore, in order to reduce this power consumption, a power amplifier with a small maximum output level is sometimes used by compensating for the nonlinear distortion generated in the power amplifier with compensation distortion generated by a distortion compensator. Sometimes it is necessary to reduce the number of adjustment steps.

[Conventional technology]

FIG. 3 is a block diagram of a conventional example, and FIG. 4 is an explanatory diagram of the operation of FIG. 3.

Note that a to e in FIG. 4 indicate spectra of portions with the same symbols in FIG. 3. The operation shown in FIG. 3 will be explained below with reference to FIG.

First, the input microwaves of frequencies ₁ and ₂ (see Figure 4 a) are split by hybrid 1, and then
As shown in FIG. 4b, the phase is shifted by the phase shifter 2, and is amplified by the distortion generating amplifier 4, which has the same amplification characteristics as the power amplifier _{7 .} The signal attenuated by the variable attenuator 8 constructed as shown in FIG. 4c is combined by the hybrid 3 to output a signal as shown in FIG. 4d.

This output signal is amplified by the power amplifier 7,
The third-order distortion components (f ₁ −2f ₂ ) and (2f ₂ −f ₁ ) shown in FIG. 4e that occur at this time are in opposite phase to the compensation distortion,
Since the amplitudes are equal, they are canceled and there is no _distortion1
and ₂ waves are output. Note that the distortion that falls within the band is often due to third-order distortion.

Here, if the variable attenuator 8 uses a circulator with a large phase temperature characteristic, the phase of the compensation distortion will change due to a change in the ambient temperature, and the phase shifting means will need to be readjusted. The same effect as a circulator is achieved by using fewer hybrids 5 and 6, and the operation of this part is as follows.

First, the diodes D ₁ and D ₂ in this attenuator are, for example, pin diodes, and ideally when the bias voltage applied to these diodes is 0, the impedance is infinite, and when it is V ₁ , the impedance is short-circuited. Since the microwaves applied here are totally reflected, the amount of attenuation is infinite (actually about 20 dB). Therefore, if the bias voltage is changed, the amount of attenuation changes from 0 to infinity.

Also, assuming that the microwave applied to the terminal of the hybrid is in phase with the terminal and appears at -90 degrees at the terminal, the microwave totally reflected by the two diodes D ₁ and D ₂ will appear at 0 degrees at the terminal →→ So, the terminal →→ is -90 degrees, and the terminal →→
is -90 degrees, and the terminal →→ returns at -180 degrees, so the terminal has the opposite phase and does not appear on the input side, so it has the same effect as a circulator.

[Problem that the invention seeks to solve]

However, a diode in the microwave band is equivalently considered to be composed of a resistance component and a reactance component, so when the bias voltage is changed to change the amount of attenuation, the reactance component also changes and the phase changes slightly.

Therefore, the amount of phase shift of the phase shifter 2 must be readjusted in order to obtain a spectrum as shown in FIG. 4d, which poses a problem in that the number of adjustment steps increases.

[Means for solving problems]

As shown in FIG. 1, the above problem is caused by splitting the input signal by a branching means 9, and converting one branched signal into a main signal component whose phase is shifted by a phase shifting means 10, and the other branched signal into a distortion generating amplification means. A synthesis means 12 synthesizes the main signal component amplified and generated in step 11 with compensation distortion added thereto, and inputs compensation distortion having an opposite phase shift and equal amplitude to the distortion generated in the compensated amplifier. In a distortion compensator that is added to and outputs a signal, a distortion level adjustment means 14 for adjusting the level of the input signal is provided before the branching means 9, and the distortion level adjustment means 9 connects the phase shift means 10 and distortion generation amplification. This problem is solved by the distortion compensator of the present invention, which adjusts the level ratio of the main signal component and the compensation distortion component in the output signal by simultaneously adjusting the level of the input signal input to the means 12.

[Effect]

In the present invention, when the level of the input signal is changed, the third-order distortion component changes by three times the amount of change in the level of the input signal, so the distortion level adjustment means 1 provided before the branching means 9
4 makes it possible to control the level of the third-order distortion component on the output side of the combining means 12, but since this is before branching, the passing phase change due to the level adjustment of the distortion level adjusting means and the characteristic change due to temperature are separated. Since it affects both parts in the same way, the output side of the combining means 12 is not affected at all.

Therefore, a circulator is used in the distortion level adjustment means 14 to adjust the distortion level with good isolation, and the distortion generation amplification means 11
A semi-fixed attenuator was inserted to prevent the amount of attenuation from changing, thereby preventing the occurrence of phase shifts and eliminating the need for readjustment, thereby reducing the number of adjustment steps.

〔Example〕

FIG. 2 shows a block diagram of an embodiment of the invention.

The same reference numerals throughout the drawings indicate the same objects, circulators 141, 142, variable attenuator 143.
and resistors R ₅ and R ₆ are distortion level adjusting means 14, hybrid 91 and resistor R ₇ are branching means 9, distortion generating amplifier 111 and semi-fixed attenuator 112 are distortion generating amplifying means 11, hybrid 121 and resistor R ₈ are composite The components of the means 12 are shown.

Moreover, R ₅ to R ₁₀ are terminating resistors. The operation will be described below with reference to FIG. 2 with reference to FIG. 4.

First, the input signal passes through a circulator 141, a variable attenuator 143 using a pin diode, and a circulator 142, and then is branched at a hybrid 91, phase-shifted by a phase shifter 10, and amplified by a distortion generating amplifier 111 for compensation. The hybrid 121 synthesizes the generated distortion and the one that has passed through the semi-fixed attenuator 112 .

Then, the composite signal having the spectrum shown in FIG. 4d is adjusted to a predetermined level by the circulator 131, variable attenuator 133, and circulator 132 that constitute the variable attenuator 13 for gain adjustment, and then the synthesized signal is sent to the compensated amplifier (not shown). added to.

Here, the variable attenuator 143 is for adjusting the distortion level for compensation, and when the attenuation amount is reduced by 1 dB, the output of the phase shifter 10, that is, the main signal (referring to the signal components of f ₁ and f ₂ ) 1dB higher, distortion generating amplifier 11
In the output of the hybrid 121, the main signal becomes 1 dB higher and the 3rd order distortion component becomes 3 dB higher, so when these are combined by the hybrid 121, the main signal becomes 1 dB higher and the 3rd order distortion component becomes 3 dB higher. Therefore, if the main signal is attenuated by 1 dB with the variable attenuator 133 after passing through the circulator 131, the main signal becomes 0 dB.
The third-order distortion component becomes +2 dB, and only the distortion component changes.

Furthermore, if the attenuation amount of the variable attenuator 133 is increased by 1 dB and the attenuation amount is decreased by 1 dB by the variable attenuator 133, the main signal remains unchanged, the third-order distortion component becomes -2 dB, and the attenuation amount of the variable attenuator 143 is adjusted. This allows the distortion level to be adjusted.

Furthermore, since the circulator is not provided in the branch line, the characteristics shown in FIG. 4d are maintained even if the ambient temperature changes, reducing the possibility of readjustment and reducing the number of adjustment steps.

〔Effect of the invention〕

As explained in detail below, the present invention has the effect of reducing the number of adjustment steps.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the principle of the present invention, FIG. 2 is a block diagram of an embodiment of the present invention, FIG. 3 is a block diagram of a conventional example, and FIG. 4 is an explanatory diagram of the operation of FIG. 3. In the figure, 9 is a branching means, 10 is a phase shifting means,
Reference numeral 11 indicates a distortion generation amplification means, 12 a synthesis means, 13 a variable attenuator for gain adjustment, and 14 a distortion level adjustment means.

Claims (1)

[Scope of Claims] 1. The input signal is split by the branching means 9, and one of the branched signals is phase-shifted by the phase shifting means 10, and the other branched signal is amplified and generated by the distortion generation and amplification means 11. The synthesizer 12 synthesizes the main signal component and the signal to which compensation distortion has been added, and outputs the input signal by adding compensating distortion of equal amplitude and inverse phase to the distortion generated in the compensated amplifier to the input signal. In the distortion compensator, a distortion level adjustment means 14 for adjusting the level of the input signal is provided at a stage before the branching means, and the input signal inputted to the phase shift means 10 and the distortion generation and amplification means 11 by the distortion level adjustment means is provided. A distortion compensator characterized in that the level ratio of a main signal component and a compensation distortion component in an output signal is adjusted by simultaneously adjusting signal levels.