JPH0416006A - Distortion compensation control method for common amplifier - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a predistortion method which is a method of compensating for intermodulation distortion generated in a common amplifier that simultaneously inputs and amplifies multi-frequency signals using a distortion compensation circuit. This paper relates to a distortion compensation control method using the method.

(Prior art and its problems) A predistortion method is one of the nonlinear distortion compensation techniques for compensating for odd-order intermodulation distortion, which is a problem in common amplifiers that simultaneously input and amplify multi-frequency signals. In this method, a distortion compensation circuit is provided in front of the common amplifier,
The intermodulation distortion contained in the output of the common amplifier is controlled by the distortion output detected from the output of the common amplifier by controlling the amplitude and phase (hereinafter referred to as control amount) of the odd-order distortion added by the distortion compensation circuit. This is a method of removing components.

In the distortion compensation control in the above predistortion method, conventionally, in order to quickly search for the control amount corresponding to the minimum value of the intermodulation distortion (hereinafter referred to as distortion output) of the common amplifier, which is the controlled amount, the maximum A known method is to update the control amount using the gradient method.

However, control using the maximum slope method is effective in cases where the distortion output changes slowly and in a relatively negative manner with respect to changes in the control amount, as in the example of the distortion output characteristics shown by the broken line (■) in Figure 1. The actual distortion output characteristics are not uniform with respect to changes in the control amount, as shown by the solid line in the figure.
Changes are small in most areas, and in many cases the minimum point is at the bottom of a valley of steep change.

FIG. 2 shows an example of actual measurement, in which the phase is used as a parameter.

Under these conditions of actual distortion output characteristics, if control is performed using only the conventional maximum slope method described above, the direction in which to search for the minimum point will not be determined in areas with little change, and the amount of change in the control amount ( Since the update width) also becomes extremely small, it does not converge to the minimum point, causing control to stagnate.

On the other hand, in a steep valley where the change is extremely large, the change in the control amount becomes very large (the change exceeds the minimum point at the bottom of the valley), and the control convergence time is repeated. This may cause stability problems.

(Object of the Invention) The present invention provides a distortion compensation control method for a common amplifier that eliminates problems of control stagnation and instability that occur in the conventional method in distortion compensation control in the predistortion method. or purpose.

(Structure and operation of the invention) [Structure] FIG. 3 is a diagram showing an example of a structure for implementing the distortion compensation control method according to the present invention.

1 is a distortion compensation circuit for compensating the distorted output included in the output of the common amplifier; 11 is a delay circuit that delays the input wave by a predetermined time; and 12 is a compensation injected to compensate for the distorted output using the bridistortion method. This is a distortion generation circuit that generates distortion waves for use. Note that the delay time of the delay circuit 11 is set to match the time required to generate the compensation distorted wave.

] 3 is a combiner that combines an input wave and a compensation distorted wave, 2 is a common amplifier that amplifies multiple frequencies simultaneously, 3 is a distortion checker circuit that detects the distorted output included in the output of the common amplifier 2, and 4 is a detection circuit. a distortion determination circuit that compares and determines whether the distorted output is larger or smaller than a predetermined threshold; 5 is a distortion control that controls the control amount of the compensation distorted wave generated by the distortion generation circuit according to the determination output of the distortion determination circuit; It is a circuit.

[Effect]

A distortion detection circuit 3 detects the distortion output included in the output of the common amplifier 2, and inputs it to a distortion determination circuit 4 and a distortion control circuit 5.

The distortion control circuit 5 receives the information from the distortion determination circuit 4 and the information from the distortion detection circuit 3, and performs distortion generation circuit 120 restriction so that the distortion output detected from the output of the common amplifier 2 is minimized. .

FIG. 4 is a schematic flowchart of the processing of the distortion control circuit 5. In the figure, 41 to 47 are step numbers.

Step number 41 is an initial process in which an initial value of the control amount at the start of control is determined.

If the distortion detection circuit 3 detects a distortion output larger than or equal to a predetermined distortion determination threshold at the start of distortion control, the control amount is roughly changed in all directions of the control region, and the distortion output obtained from the distortion detection circuit 3 is Among them, the control amount that provides the minimum distortion output is set as an initial value (initial control amount). That is, by roughly scanning the entire control region, it is possible to roughly estimate where the point where the distortion output is minimum exists, and avoid stagnation in control.

42 is a distortion specific force detection process, in which the distortion output is extracted from the output of the common amplifier 2 and the next step is a threshold value judgment process 43
In order to execute this, the signal is simultaneously supplied to the distortion determination circuit 4.

43 is a distortion output value determination process in which the distortion determination circuit 4 compares the distortion output obtained in the distortion output detection process with a distortion determination threshold value.

If the distortion output obtained by the initial control amount is smaller than the threshold value, the process proceeds to fine control processing 44, and if it is equal to or greater, the process proceeds to coarse control process 45. In other words, if the distortion output due to the initial control amount is greater than or equal to the distortion determination threshold, it is determined that the change in distortion output relative to the control amount is in a small region (see Figure 1), and the control amount is updated to a larger value. Increase stopping speed.

In addition, if the distortion output due to the initial control amount is smaller than the distortion determination threshold, it is determined that the current control amount or distortion output is at a steep valley, and the distortion output is determined by performing more detailed control. Converge the control without exceeding the minimum point of .

Reference numeral 44 denotes a fine control process in which the update range of the control amount is made small and fine control is performed, and fine control is performed by one of the following methods.

(1) A fixed width update is performed in which the control amount is updated in the direction of decreasing the distortion output by a certain small fixed value, and the control amount is updated using the maximum slope method.

(2) Select a small value for the update slope coefficient (described later).

However, the update width δ of the control amount by the maximum slope method is generally given by the following equation.

δ=K・ΔD Here, K: Update slope coefficient ΔD: Amount of change in distortion output due to previous control.

45 is a coarse control process in which the control amount is updated in a predetermined large fixed value width. Regardless of the magnitude of the change in distortion output relative to the control amount, the control amount is updated relatively to increase the processing speed.

46 is a static value checking process for the distortion output, in which the end condition of the rough control in step 45 is detected and judged, and if a static value is detected, the process moves to fine control in step 44; if not detected, the process returns to step 42. and continue.

Similar to step 46, 47 is a pressure detection process for the termination condition of the close control in step 44, and if the strain output remains the same, the process is terminated; otherwise, the process returns to step 43 to continue.

(Effects of the Invention) As described in detail above, according to the present invention, it is possible to avoid control stagnation by automatically setting the initial control amount, and to set the predetermined distortion determination threshold and the initial control amount. By changing the method of updating the control amount depending on the magnitude relationship with the distortion output by There is.

[Brief explanation of drawings]

Fig. 1 is a side view of distortion output characteristics with respect to the control amount, Fig. 2 is a side view of actual measurement of distortion output characteristics with respect to the control amount, Fig. 3 is an example of a configuration of distortion compensation control implementing the present invention, and Fig. 4 is the main 3 is a flowchart of a distortion compensation control method according to the invention. 1... Distortion compensation circuit, 11... Delay circuit, 1
2...Distortion generation circuit, 13...Synthesizer, 2...
・Common amplifier, 3...distortion detection circuit, 4...
Distortion determination circuit, 5...Distortion image production circuit, 41-47...
・Step number.

Claims (2)

[Claims] (1) Distortion compensation inserted at the front stage of the common amplifier using the distortion output detected from the output of the common amplifier to remove odd-order intermodulation distortion included in the output of the common amplifier that amplifies multi-frequency signals. In a common amplifier distortion compensation control method using a predistortion method that controls the amplitude and phase control amount of odd-order distortion added in a circuit, the control amount is coarsely adjusted over the entire control region before starting distortion compensation control. The control amount that provides the minimum distortion output among the distortion outputs obtained by changing the distortion output is set as the initial control amount, and the distortion output detected by the initial control amount is compared with a predetermined threshold value to determine the distortion. When the output is greater than or equal to the threshold, coarse control is repeatedly performed to update the control amount in a direction in which the distortion output decreases within a predetermined fixed value range until a static value of the distortion output is detected. , when the distortion output detected by the initial control amount is smaller than the threshold value or when the stationary value is detected, the distortion output is decreased by a fixed value smaller than the width of the predetermined fixed value. A distortion compensation control method for a common amplifier, in which detailed control of updating the control amount by small fixed width updating and updating using a maximum slope method is repeated until the distortion output is stopped. (2) Distortion compensation inserted at the front stage of the common amplifier using the distortion output detected from the output of the common amplifier to remove odd-order intermodulation distortion included in the output of the common amplifier that amplifies multi-frequency signals. In a common amplifier distortion compensation control method using a predistortion method that controls the amplitude and phase control amount of odd-order distortion added in a circuit, the control amount is roughly varied over the entire control region before starting distortion compensation control. The control amount that yields the minimum distortion output among the distortion outputs obtained by the control is set as an initial control amount, and the distortion output detected by the initial control amount is compared with a predetermined threshold value to determine the distortion output. is greater than or equal to the threshold, repeating coarse control to update the control amount in the direction of decreasing the distortion output within a predetermined fixed value range until a static value of the distortion output is detected; When the distortion output detected by the initial control amount is smaller than the threshold value or when the stagnant value is detected, the control amount is updated by the update slope coefficient, and dense control is performed until the distortion output remains the same. Distortion compensation control method for a common amplifier in a repetitive manner.