JP3037538B2 - Multi-frequency common amplifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-frequency common amplifier used for a mobile telephone base station or a mobile telephone repeater, for amplifying multi-frequency signals simultaneously.

[0002]

2. Description of the Related Art A base station and a wireless relay device in an 800 MHz band mobile telephone system and the like are provided with a multi-frequency common amplifier for simultaneously amplifying multi-frequency signals. In this multi-frequency common amplifier, it is necessary to sufficiently improve linearity in order to minimize intermodulation distortion, and a small-sized circuit for obtaining high linearity is used. As such a circuit, there is a nonlinear distortion compensating circuit, but there is a disadvantage that the linearity is deteriorated due to a change in ambient temperature or aging. As a remedy for this, one of the pre-distortion nonlinear distortion compensation circuits is a common amplifier that compensates for the third-order intermodulation distortion, and when power is turned on or when the temperature inside the device changes, or periodically, The input signal is amplified by switching to two pilot signals having different frequencies within the band, and a third-order distortion component due to the two-wave pilot signal is detected, and the amplifier is shifted so as to cancel the third-order distortion component. After adjusting the amount of phase and the amount of attenuation (amplification), the input signal side is switched again to amplify the multi-frequency input signal (IEEE T).
rans. Veh. Technol. , Vol. VT-
34, no. 4, pp. 169-177, Nov. 19
85).

Another is a self-adjustable feedforward amplifier (SAFF-A: Self-Adjustin).
g Feed-Forward Amplifier)
It is a common amplifier that compensates for all intermodulation distortion and noise by self-adjustment. This circuit includes an error detection loop and an error elimination loop, detects a distortion component other than the input signal in an error detection loop including a main amplifier which is a compensation target amplifier, and converts the detected distortion component (error component) to an auxiliary amplifier. (Amplifier), which is configured to amplify an error component and then combine it with a multi-frequency input signal in the opposite phase to cancel the error component. Equipped with a pilot transmitter and its receiver to minimize the detection distortion after injection (Nojima, Narahashi: Ultra-low distortion multi-frequency common amplifier for mobile communication, IEICE Technical Report, v
ol. 90. No. 57, RCS90-4).

FIG. 3 is a block diagram of a conventional self-adjustable feedforward amplifier and a frequency spectrum of a main part. In the figure, 1 is a distributor for distributing an input signal, 2 is a variable phaser, 3 is a variable attenuator, 4 is a main amplifier, 5 is a delay line, 6 is a distribution combiner, 7 is a variable phaser, and 8 is variable. Attenuator, 9 is an error amplifier, 10 is a delay line, 11 is a combiner, 1
5 is a directional coupler for injecting a pilot signal from a pilot signal generator (P-SG) 16, 17 is a directional coupler for extracting a pilot signal, and 18 is a pilot signal receiving and distorting the pilot signal. It is a pilot receiver (P-Rx) that detects the level of a component. First, the basic operation when there is no pilot signal will be described. The multi-frequency input signal is input to the terminal a of the distributor 1 via the directional coupler 15, and is output from the terminal c. The multi-frequency signal output from the terminal c is amplified by the main amplifier 4 via the variable phase shifter 2 and the variable attenuator 3. The output includes a distortion (error) component generated at the time of amplification, and is input to the a terminal and the d terminal of the distributor / synthesizer 6 and the b terminal of the synthesizer 11 via the delay line 10. This 1a → 1c → 2-4 → 6a → 6d → 10
→ Let X be the route to 11b. On the other hand, the multi-frequency input signal output from the d terminal of the distributor 1 is input to the b terminal of the combining / distributing device 6 via the delay line 5 and becomes an inverted-phase signal with inverted polarity to be combined with the input signal from the a terminal. Is done. As a result, a distortion component is extracted and output from the terminal c. The distortion component output from the terminal c is amplified by the error amplifier 9 via the directional coupling 17, the variable phase shifter 7, and the variable attenuator 8, and is input to the terminal a of the synthesizer 11. This 1a → 1d → 5 → 6b
The route from → 6c → 17 → 7 to 9 → 11a is defined as Y.

The combiner 11 reverses the polarity of the signal containing the distortion component input to the terminal b via the path X and the signal of the distortion component input to the terminal a of the combiner 11 via the path Y. The distortion component is canceled by synthesis, and a multi-frequency common amplified signal with little distortion is output from the terminal c. That is, the route 1a → 1c → 2
→ 3 → 4 → 6a → signal and route 1a → 1d → 5 →
The signal passing through 6b is adjusted in time by the delay line 5, the variable phase shifter 2 and the variable attenuator 3 are adjusted, the input signal is canceled by the combining / distribution by the combining / distributing unit 6, and the distortion component is extracted from 6c. And a signal passing through the route 6d → 10 → 11b,
The signal passing through the route 6c → 7 → 8 → 9 → 11a and the delay line 1
The delay time is adjusted to 0, the variable phase shifter 7 and the variable attenuator 8 are adjusted, and the combiner 11 combines the phases in opposite phases to cancel out the distortion component and output a multi-frequency amplified signal with distortion compensation from 11c.

Next, a case where a pilot signal is injected into an input signal of two frequencies will be described. The frequency spectrum of each unit shown in FIG. 3 is represented by including the polarity with the horizontal axis representing the frequency and the vertical axis representing the level. When the pilot signal p is injected from the pilot signal generator 16 into the two-frequency input signal input to the directional coupler 15, the signal input to the terminal a of the distributor 1 has a frequency spectrum indicated by 1a. When this signal reaches 6a via paths 1c → 2-4, it becomes a frequency spectrum indicated by 6a to which a distortion component is added. Similarly, the spectrum becomes like 6b, 6d, 6c, 11a, 11c. In this case, the signal of the terminal 6c is extracted by the directional coupler 17 and the pilot signal receiver 18
Then, if the level is detected, and the variable phase shifter 2 and the variable attenuator 3 are adjusted so that the detection level is minimized, the distortion detection loop can be adjusted. The distortion detection loop is 1a →
1c → 2 to 4 → 6a → 6b → 5 → 1d → 1a For reference, FIG. 4 shows the improvement amount of distortion compensation by the amplitude deviation and the phase deviation (excerpted from RCS90-4 ultra-low distortion multi-frequency common amplifier for mobile communication).

[0007]

However, in the case of the former pre-distortion type, since the input signal is switched to the calibration pilot signal and inputted, there is a problem that the communication service during that period is interrupted. Also,
In the case of the latter self-adjustment type feedforward amplifier, if the frequency of the pilot signal to be injected to adjust the distortion detection loop is within the band, the intermodulation distortion of the multi-frequency input signal can be adjusted during operation. Cannot accurately detect the pilot signal. Therefore, when the injection level of the pilot signal is increased, a spurious response appears in the output signal. Therefore, the frequency of the pilot signal is set to a frequency outside the band. However, the difference between the transmission characteristics outside the band of the amplifier, that is, the phase characteristics and the attenuation characteristics with the characteristics within the band increases as the frequency band is separated, so that the out-of-band frequency is set as close to the band as possible. There is a disadvantage that the optimal adjustment of the compensation amount cannot be performed. Moreover, a filter is required to remove spurious signals generated by the pilot signal,
This hinders miniaturization and cost reduction.

An object of the present invention is to provide a highly stable self-adjustable feed-forward multi-frequency common amplifier in which the adjustment of the distortion detection loop is always performed stably without using a pilot signal for adjusting the amount of distortion compensation. To provide.

[0009]

SUMMARY OF THE INVENTION A multi-frequency common amplifier according to the present invention comprises a first divider for distributing an input signal, a first variable phase shifter having a first output terminal connected to one of the output terminals of the first divider. The signal passing through the variable attenuator and the main amplifier and the signal passing through the first delay line from the other output terminal are subjected to reverse-phase synthesis by a combiner / distributor to detect and output a distortion component generated in the main amplifier. A distortion detection loop, a signal of a distortion component that has passed through a second variable phase shifter, a second variable attenuator, and an error amplifier from one output terminal of the combiner / distributor, and a second delay line from the other output terminal. A multi-frequency common amplifier based on feedforward distortion compensation comprising an error removal loop that removes the distortion component by outputting a multi-frequency amplification signal by performing a reverse phase synthesis of the signal including the passed distortion component with a combiner to remove the distortion component. Input signal before the distributor A second divider for branching and outputting a signal; a detector for detecting an output of the second divider and outputting input signal information; and a second divider between the combining divider and the second variable phase shifter. A third divider that is inserted and branches and outputs a distortion component output output from the combiner / divider; a fourth divider that distributes and outputs the output of the third divider to at least two or more; A plurality of rectifiers having different sensitivities for respectively rectifying and outputting the two or more outputs from the fourth distributor; detecting an input signal level from input signal information from the detector; The first of the distortion detection loops so that the outputs from the plurality of rectifiers are minimized.
And a control circuit for controlling the value of the first variable attenuator.

[0010]

FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, reference numerals 1 to 11 are the same as those of the conventional circuit of FIG. 19 and 20 are distributors, 21 is a detector, 22 is a distributor, 23 is a rectifier, 24 is an amplifying rectifier having an amplifying and rectifying function, and 25 is a control circuit. FIG. 2 shows the frequency spectrum at the terminals 6a, 6b, 6c of the combiner / splitter 6 of FIG. 1, the vertical axis represents the level (dB), and the horizontal axis represents the frequency. The operation of the present invention will be described with reference to FIGS. First, the case where the input level is the maximum will be described. The thick line 6c in FIG. 2 indicates when the variable phase shifter 2 and the variable attenuator 3 have been adjusted to the best values, and the dotted line indicates when the adjustment has deviated. The output of the terminal 6 c is partially extracted by the distributor 20, further distributed by the distributor 22, and input to the rectifier 23 and the amplification rectifier 24. When the rectifier 23 is in the state indicated by the dotted line in the state 6c of FIG. 2A, the rectified voltage of the rectifier 23 is high (however, the rectifier 23 is in a linear state), and the voltage is input to the control circuit 25. The control circuit 25 operates the variable phase shifter 2 and the variable attenuator 3 so that the voltage of the rectifier 23 decreases. In this case, the minimum value is substantially a solid line 6c in FIG.
Therefore, the distortion component can be extracted by sufficiently suppressing the input wave. Even if the input wave reaches the level of the solid line, the error amplifier 9
There is no problem in the cancellation in the loop, since no distortion is caused by this. In this example, 30 dB is suppressed. Therefore, the fluctuation of the output when canceling in the loop is extremely small. For example, if the ratio between the same component as the input frequency in the spectrum of 11b and the same component as the input frequency in the spectrum of 11a is different by 30 dB, the output fluctuation is extremely small at worst as shown in the following equation.

[0011]

## EQU1 ## 20 log (1 ± 0.0316 (−30 dB value))
= ± 0.27dB

Next, when the input level is low, FIG.
(B). The state when the input level is lower by 20 dB than in the case of the above (A) is shown. Distributor 2
2 is rectified by the rectifier 23, but a normal rectifier can only provide a dynamic range of about 30 to 40 dB. Therefore, as shown by 6c in FIG. It can only be detected up to the level. However, the error amplifier 9 of the error elimination loop generates little distortion up to the input of the level (ii) and does not cause any particular problem. However, the level difference of the same spectrum component as that of the input waves 6a and 6c in FIG. 2B is small (10 dB in this example), and finally the combiner 1 of the error elimination loop is used.
When the distortion component is canceled by 1, the level ratio is the same,
The level fluctuation of the output wave becomes large. For example, 10
The following equation is obtained by combining signals of different dB.

[0013]

## EQU2 ## 20 log (1 ± 0.316 (−10 dB value)) =
Therefore, suppression of the same frequency component as the input wave of (B) 6c requires about 30 dB as shown by the solid line. Therefore, when the output of the rectifier 23 becomes small and becomes a certain value or less, the output of the amplification rectifier 24 is monitored, and the variable phase shifter 2 and the variable attenuator 3 are controlled by the control circuit 25 so that the voltage becomes minimum. Controlled by. Although the above description has been made for the case of two-wave input for simplicity, the number of input channels is 0 in a normal case.
~ N waves. Therefore, when the number of channels is large, control is performed so that the entire output level becomes small. In the present invention, two rectifiers and only one detector are provided for an automobile telephone system. However, in order to further cope with a low input, a rectifier and a detector may be added by a similar circuit configuration.

The control circuit 25 sends the optimal data stored in advance to the variable phase shifter 2 and the variable attenuator 3 when the initial power is turned on. Further, during the operation, if the input wave disappears, the detection becomes impossible. Therefore, the optimum update data is always sent out and stored to prepare for the input electric field “present”. The input electric field information is branched by the distributor 19 and detected by the detector 21.
The signal is input to the control circuit 25 and the input level is determined. In order to operate the present circuit when it changes from the optimum value due to temperature change and aging, threshold values are set in the rectifiers 23 and 24 corresponding to the input levels, respectively, and are used as judgment levels. Therefore, the threshold level of the rectifier 24 is determined for each input level, and control is performed so as to be equal to or lower than the threshold level. In the example of FIG. 2, the threshold level of the rectifier 23 is set to the level (ii) of (A) 6c so that the input electric field can be adjusted to be high or low, and the amplifying rectifier 24 can set the level of (B) 6c. (iii) (the input electric field is medium or low), and (B) the level of 6c (iv) (the input electric field M
IN). This threshold level may be further subdivided or may be set continuously.

[0015]

As described above in detail, the distortion detection loop monitors the level of the entire band with the distortion detection output without using the pilot signal and is controlled so that the distortion becomes the minimum value. Thus, stable distortion compensation can be maintained without generating a spurious response.

[Brief description of the drawings]

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

FIG. 2 is a frequency spectrum of a main part of FIG.

FIG. 3 is a circuit diagram of a conventional circuit and a frequency spectrum of a main part.

FIG. 4 is an explanatory diagram of a distortion improvement amount.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Divider 2,7 Variable phase shifter 3,8 Variable attenuator 4 Main amplifier 5,10 Delay line 6 Synthetic distributor 9 Error amplifier 11 Synthesizer 15,17 Directional coupler 16 Pilot signal generator 18 Pilot signal receiver 19, 20, 22 Distributor 21 Detector 23 Rectifier 24 Amplification Rectifier 25 Control Circuit

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-83407 (JP, A) JP-A-4-156704 (JP, A) JP-A-4-190393 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H03F 1/30-1/40

Claims (1)

(57) [Claims] A first splitter for splitting an input signal, and a first variable phase shifter connected to one output terminal of the first splitter.
A signal that has passed through the first variable attenuator and main amplifier and a signal that has passed through the first delay line from the other output terminal are out-of-phase combined by a combiner / distributor to detect a distortion component generated in the main amplifier. A distortion detection loop to be output, a signal of a distortion component that has passed through a second variable phase shifter, a second variable attenuator, and an error amplifier from one output terminal of the combiner / distributor, and a second signal from the other output terminal.
Multi-frequency common amplifier based on feed-forward distortion compensation comprising an error elimination loop that removes the distortion component and outputs a multi-frequency amplified signal by synthesizing the signal containing the distortion component through the delay line in reverse phase with a combiner. , A second divider inserted before the first divider and branching and outputting an input signal; a detector for detecting an output of the second divider and outputting input signal information; A third divider inserted between the combiner / divider and the second variable phase shifter for branching and outputting a distortion component output output from the combiner / divider; A fourth divider for dividing and outputting at least two or more, a plurality of rectifiers having different sensitivities for respectively rectifying and outputting the two or more outputs from the fourth divider, and Detects input signal level from input signal information A control circuit for controlling the values of the first variable phase shifter and the first variable attenuator of the distortion detection loop so that the output from the plurality of rectifiers is minimized according to the input signal level. Characteristic multi-frequency common amplifier.