JPH01278109A - Automatic output level control system - Google Patents

Abstract

PURPOSE:To improve convergence properties for control by approximating the control voltage-output power characteristics of a power amplifier with a straight line to define the characteristics to be stored in a P-V table. CONSTITUTION:A CPU 12 reads the control voltage shown in the digital value out of a P-V table 19 in accordance with the digital value showing the output power set via a serial port 17 and applies said control voltage to a power amplifier 11 via a I/O register 18 and a D/A converter 14. Thus the amplifier 11 amplifies the main signal and produces the output. Then the characteristics defined by approximating the outside of a control range of the actual control voltage-output power characteristics with a straight line obtained by extending the characteristics inside the control range is set to the table 19. As a result, the control convergence properties are constant even in case the output voltage of the amplifier 11 is kept at a point near the saturated part of the control voltage-output power characteristics close to the upper limit value of the control range. Thus it is possible to improve the control accuracy and to shorten the converging time.

Description

[Detailed Description of the Invention] [Summary] Regarding the automatic output level control method used when automatically controlling the output level of a power amplifier, an error equivalent to the error between the set value and the detected value in the output is controlled. In order to improve the convergence of control by making it possible to obtain the voltage, we created a P-■ table that stores the control voltage vs. output power characteristics of the power amplifier and the characteristics of the output power vs. output detection voltage of the power amplifier. ■-P table stored in the table, and the P-P table is stored in
■The output power is set by comparing the output power read from the V-P table with the set value and correcting the control voltage corresponding to the output detection voltage when the control voltage read from the table is applied to the power amplifier. In the automatic output level control method of a power amplifier that converges to a value of P
-Characteristics stored in the V table for power amplifier control voltage-
It is constructed by approximating the output power characteristics with a straight line.

[Industrial application field]

The present invention relates to an automatic output level control method used to automatically control the output level of a power amplifier, and more particularly to an automatic output level control method that can speed up convergence to a set value.

For example, in a device that uses a power amplifier, the output power of the power amplifier easily changes with fluctuations in external conditions such as ambient temperature, so automatic output level control (ALC) is used to keep the output power constant.

In such an automatic output level control method, it is necessary that the control convergence time is short and the control accuracy is high.

[Conventional technology]

FIG. 3 shows a conventional automatic output level control system, and exemplifies a case where it is constructed using a central processing unit (CPU) and a ROM table for converting control voltage and output power.

In FIG. 3, when setting the output power of the power amplifier 11, an output power setting signal t-CPU 12 consisting of a digital value is supplied from the outside. The CPU 12 uses the ROM table 13 to convert the set output power value into a control voltage consisting of a digital value. A digital-to-analog (D/A) converter 14 converts this value into an analog value and supplies it to the power amplifier 11 as a control voltage. The power amplifier 11 amplifies the main signal according to this control voltage and generates output power. The detector 15 detects the output of the power amplifier 11 and generates an analog voltage output according to the output power. An analog-to-digital (A/D) converter 16 converts this value into a digital value and provides it to the CPU 12.

The CPU 12 uses a table separately stored in the ROM table 13 to read the output power value from the output detection voltage. The CPU 12 compares the read power value (detected value) with the set power value (target value), and corrects the control voltage value given to the power amplifier 11 according to the difference. By repeatedly performing such control, the output power of the power amplifier 11 converges to the target value.

In this case, the ROM table 13 contains the value of the actual control voltage-output power characteristic curve for generating the control voltage for the power amplifier 11, and the bait of the output power-output detection voltage characteristic curve for reading the output power of the power amplifier 11. Stored.

Fig. 4 shows an example of a control voltage-output power characteristic curve of a power amplifier. Within the control range, the control voltage-output power characteristic is almost linear, but outside the control range (
It has been shown that saturation characteristics occur at the upper limit).

[Problem to be solved by the invention]

The control voltage-output power characteristic curve used in the conventional automatic output level control system has a saturation characteristic as shown in FIG. Therefore, when the output power is outside the control range (saturation region), the error in the control voltage becomes larger than the error between the set value and the output value (detected value), resulting in poor convergence to the set value. .

Figure 5 explains the error in the control voltage in the conventional system. = Assuming that the output value of the power amplifier for a certain output power setting value is the value shown in the figure, the output power of the power amplifier - output detection voltage characteristic curve B The error in the output detection voltage read from is Δv1. On the other hand, the error ΔV in the control voltage corresponding to the output value at this time is read from the control voltage - output power setting value, but since the characteristic person exhibits saturation characteristics, the error Δv2 is predicted from the error Δv1 in the output detection voltage. Things get bigger.

The present invention aims to solve the problems of the prior art, and sets a straight line within the control range to the outside of the control range as the control voltage-output power characteristic in a ROM table to determine the output power. The purpose is to improve the convergence of control by adjusting K so that an error equivalent to the error between the set value and the detected value is obtained in the control voltage.

[Means to solve the problem]

The automatic output level control method of the present invention, as shown in the embodiment of FIG. v-p table 20 storing
P- in response to the externally set output power.
The control voltage read from the V table 19 is applied to the power amplifier, and the output power read from the V-P table is compared with the set value corresponding to the output detection voltage at this time, and the control voltage to be applied to the power amplifier is determined according to the error. In an automatic output level control method for a power amplifier that converges the output power to a set value by controlling to correct it, the control voltage of the power amplifier -
The output power characteristic is approximated by a straight line.

[Effect]

In the power amplifier automatic output level control system, P-
The power amplifier is provided with a V table and a v-P table, and a control voltage read from the P-■ table is applied to the power amplifier in accordance with the output power set from the outside, and the control voltage is applied to the power amplifier in accordance with the output detection voltage of the power amplifier at this time. Control is performed to converge the output power to the set value by comparing the output power read from the P table with the set value and correcting the control voltage according to the error.

Conventionally, the P-■ table stores the power amplifier's control voltage-output power characteristics, and the v-p table stores the power amplifier's output power-output detection voltage characteristics. The control voltage-output power characteristic exhibits a saturation characteristic outside the control range, and the error in the control voltage is as large as the error between the set value and the detected value in the output, so that control convergence during corrective operation is delayed.

In the automatic output level control method of the present invention, the characteristics stored in the PV table are a straight line approximation of the control voltage-output power characteristics of the power amplifier, so the error is equivalent to the error between the set value and detected value in the output. is obtained at the control voltage, the control convergence is improved.

Figure 6 shows an example of a ROM table curve with an extended linear range.The actual curve of control voltage-output power characteristics shows saturation characteristics outside the control range, but the ROM table curve shows saturation characteristics outside the control range. It is shown that the curve is also determined to be a straight line.

By doing so, the error in the control voltage is reduced even when the detected output value is outside the control range. Therefore, it is easy to converge to the set value, and the convergence time in automatic output level control can be shortened.

〔Example〕

FIG. 1 shows an embodiment of the automatic output level control system of the present invention, in which the same parts as in FIG. 3 are designated by the same numbers, and 17 is a serial port for inputting control signals from the outside. , 18 is the power amplifier 11 side and the CPU 12
The I10 register inputs and outputs signals between the power amplifier 11 and the power amplifier 11.
-v table, 20 is a v-P table storing output power-output detection voltage characteristics of the power amplifier 11, and 21 is a comparator.

Further, FIG. 2 is a diagram explaining the operation in the embodiment of FIG. 1.

In FIG. 1, the CPU 12 reads the control voltage 'tP-■ table 19 consisting of digital values in accordance with the digital value indicating the output power set from the outside through the serial port 17, and outputs the D/P through the I10 register 18.
A converter 14 is provided. The D/A converter 14 converts this value into an analog value and supplies it to the power amplifier 11 as a control voltage, whereby the power amplifier 11 amplifies the raw signal and generates an output. In FIG. 2, (a) shows the initial value of the output power set in the power amplifier 11 in this way.

The detector 15 detects the output of the power amplifier 11 and generates a detection voltage consisting of an analog voltage corresponding to the output power. It is given to the CPU 12. The CPU 12 uses this value to obtain the output power read value from the v-P table 20. V-P table addition is 5th
It has a linear characteristic similar to the characteristic B shown in the figure.
Assume that the output power reading value shown in (a') is thereby obtained.

The CPU 12 compares the read output power value with the set output power value, corrects the control voltage according to the error, and resets the output power value. In this case, the reset value (b) is the set output power value. 1- (C), then Cb) = (C)+
O determined by calculating ((c)-(a'))i By repeatedly performing such control, the output power of the power amplifier 11 converges to the set value (c).

In FIG. 1, the comparator 21 is provided to control the output level of the power amplifier 11 only when the power amplifier 11 is generating an output by comparing the output of the detector 15 with a predetermined level. ing.

The automatic output level control method shown in Figure 1 performs control to gradually reduce the difference between the output power setting value (,) and the output power initial value (,), but in reality, the difference between the output power setting value (,) and the output power initial value (,) is Control is performed based on the difference between the value (C) and the output power reading value (a'). The reading) value (a') and the initial value (,) generally have different values near the upper limit of the control range, but the control voltage error ΔV corresponding to l(a') - (a)1 is small. The better the control accuracy and the better the convergence.

In Figure 2, A shows the control voltage-output power characteristics when the actual characteristics are set as a P-V table, and C shows the control voltage-output power characteristics when linearly approximated characteristics are set as the P-V table. The voltage error ΔV is smaller than the control voltage error Δv2 in case A.

In the method of the present invention, a characteristic is set in the P-■ table 19, as explained in FIG. .

Therefore, even if the output power of the power amplifier 11 is near the saturation point of the control voltage-output power characteristic near the upper limit of the control range, the convergence of the control does not change, and therefore the control accuracy can be improved and the convergence time can be shortened. become.

〔Effect of the invention〕

As explained above, according to the present invention, when automatically controlling the output level of a power amplifier, etc., the relationship between the control voltage and the output value is approximated by a straight line. In some cases, it is possible to speed up the convergence to the set value, and it is also possible to improve control accuracy.

Note that the control method of the present invention is not limited to automatically controlling the output level of a power amplifier, but is generally applicable to control systems that perform feedback operations, regardless of the type of controlled object.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram explaining the operation of the embodiment of FIG. 1, FIG. 3 is a diagram showing a conventional automatic output level setting method, and FIG. Figure 5 is a diagram showing an example of the control voltage-output power characteristic of a power amplifier. Figure 5 is a diagram explaining the control voltage error in the conventional method. Figure 6 is a diagram showing an example of a ROM table curve with an extended linear range. . 11... Power amplifier... Central processing unit (CPU) 14... Digital to analog (D/A) converter 15
...Detector 16...Analog-digital (A, /D) converter 17
... Serial port 18 ... I10 register 19 ... P-■ table 20 ... v-P tape player 21 ... comparator Figure 1 showing the actual crime I1 of the present invention Figure 12: Central processing unit (CPU) Conventional automatic output level setting method 18:, 2 T Figure 3 System (1) Voltage Control voltage of power amplifier - Whistle diagram 4 showing an example of the output power characteristic curve

Claims (1)

[Claims] P-V storing control voltage-output power characteristics of a power amplifier
A table (19) and a V-P table (20) storing the characteristics of output power vs. output detection voltage of the power amplifier.
- V-P corresponding to the output detection voltage when the control voltage read from the V table (19) is applied to the power amplifier.
In an automatic output level control method for a power amplifier that converges the output power to the set value by comparing the output power read from the table (20) with the set value and correcting the control voltage, the P-V table (19) ) is a straight line approximation of the control voltage-output power characteristic of a power amplifier.