JPH04127704A - Digital agc circuit - Google Patents

Abstract

PURPOSE:To improve precision for an output signal level by adding a register for setting the kind of an input signal and a means to correct an average value for the absolute value of the input signal corresponding to the kind. CONSTITUTION:The mode of the input signal is set from the outside to a mode setting register 106. Corresponding to the kind of the input signal to be set to this register 106, a correcting value is inputted from a correcting value controller 107 to a multiplier 103. Since the output of the multiplier 103 is made equivalent to the root of the power average value of the input signal by this multiplication, the output of a multiplier 104 can be defined as proper gain for setting the square average value of the output signal at a desired standard value. Thus, the precision for the output signal level can be improved with simple configuration.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a digital AGC circuit, and for example, to a digital AGC circuit for keeping the average level of a digitally expressed signal constant.

[Conventional technology]

An example of the configuration of the most basic conventional AGC circuit is shown in FIG. Conventionally, in the configuration as shown in FIG. 2, the output of the register 305 is initialized, the value thereof is input to the multiplier 301 and becomes the gain for the input signal, and the output of the multiplier 301 becomes the output signal. This output signal is divided into two by a squarer 302 and an averager 303.
A root mean value is calculated, and the root mean square value is subtracted from a predetermined set value by a subtractor 304. The output from the subtracter 304 is sent to the adder 30 as an error signal.
6 is added to the contents of the register 305 and input to the multiplier 301 as a new gain. By repeating the above operations, the error between the root mean square value of the output signal and the set value becomes "0", and as a result, the power level of the output signal is maintained at -χ.

[Problem to be solved by the invention]

However, in the above conventional example, when the input signal's power range increases, the number of times the gain is updated until the output voltage converges to the set value increases dramatically, resulting in a very long time. There was a problem with this. In order to solve the above problem, the configuration shown in FIG. 3, which does not use a feedback loop, can be considered. In the operation of the circuit shown in FIG. 3, the average value α of the absolute values of the input signal is calculated by the absolute value unit 201 and the averager 202. Then, by dividing a certain set value by this calculated value using the divider 203 and inputting the quotient to the multiplier 204 and using it as the gain of the input signal, it is possible to maintain the level of the output signal at a constant value. This is the solution. However, the purpose of the AGC circuit is to maintain the square root value of the output signal at the set value, and the configuration shown in FIG. 3 operates to maintain the average value of the absolute values at the set value. Therefore, it was inevitable that errors would occur in the output level. Generally speaking, if the root mean square value is represented by 2 and the average absolute value is represented by vl, then J">IVI. As a result, the value of the divisor of the divider 203 shown in FIG. is smaller than the square root. Therefore, the divider 203
The output, that is, the gain with respect to the human input signal becomes large, and as a result, the output signal becomes larger than the desired value. The disadvantage is that the error increases as the amount of change in the amplitude of the input signal increases.

[Means to solve the problem]

The present invention was made for the purpose of solving the above-mentioned problems, and includes the following configuration as one means for solving the above-mentioned problems. That is, a calculation means for calculating the average value of the absolute values of input signals, a setting means for externally setting the type of input signal, and a calculation means calculated by the calculation means according to the type of input signal set in the setting means. a correction means for correcting the average value of the absolute values to a root mean square value, a division means for dividing a specific set value by the correction value corrected by the correction means, and a quotient of the division result by the division means. and a multiplication means for multiplying the input signal by the input signal.

[Effect]

In the above configuration, in the AGC circuit which divides a desired set value by the average value of the absolute values of the input signal and uses the quotient as the gain, the mode of the input signal is set according to the register externally set and the set mote. By correcting the calculated average absolute value to match the square root of its root mean square value, the gain convergence time is shortened and the accuracy is improved.

【Example】

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram of a digital AGC circuit according to an embodiment of the present invention. In FIG. 1, 101 is an absolute value unit for taking the absolute value of the human input signal, and the output of the absolute value unit 101 is the averager 1.
02 and its average value is calculated. Averager 1
The output of 02 is connected to one input of multiplier 103. The output of the correction value controller 107 is connected to the other input of the multiplier 103, and the output of the mote setting register 106 is connected to the input of the correction value controller 107. The mode of the input signal is set in the mote setting register 106 from the outside. The output of the multiplier 103 is connected to the divisor input of the divider 104, and the square root of the root mean square value of the desired output signal level is input to the dividend input of the divider 104 as a set value. The output of the divider 104 is connected to one input of a multiplier 105, the input signal from the other input of the multiplier 105 is connected, and the output of the multiplier 105 becomes an output signal. The operation of this embodiment having the above configuration will be described below. First, the type of input signal is set in the mode setting register 106. The correction value controller 107 determines the correction value according to the type of this input signal. This correction value is determined by the amplitude characteristics of the input signal, and the input signal with a large amplitude change has a large correction value. For example, when the input signal is a sine wave, the correction value is as follows. This correction value “1.11” is input to the multiplier 103. Note that this value can also be applied to FSX modulated input signals. That is, even when a code corresponding to a sine wave or FSX modulated wave is set in the mode setting register 106, the correction value controller 107 sets the correction value "1.11" to the multiplier 10.
3 is input. In addition, in the case of PSK modulated waves, the correction value becomes larger,
In the case of a CAM modulated wave, the value becomes even larger. For example, in the case of a PSK modulated wave according to CCITT Recommendation V, 27ter, the correction value is approximately 1.15, and QAM according to ■, 29
The correction value in the case of a modulated wave is a little over 12. That is, the above-mentioned correction value corresponding to the type of human input signal set in the register 106 is input from the correction value controller 107 to the multiplier 103. As a result of this multiplication, the output of the multiplier 103 becomes equivalent to the square root of the mean square value of the input signal.
The output can have an appropriate gain to bring the mean square value of the output signal to the desired standard value. Also, the multiplier 103 in FIG. 1 is deleted and the divider 104 is
Directly input the average value of the absolute values of the input signal into the divisor input of
A similar operation is also possible with a configuration in which the correction value controller 107 switches the set value of the dividend input of the divider 104 according to the correction value. As explained above, according to this embodiment, the type of input signal is applied to the AGC circuit whose gain is the quotient of the square root of the root mean square value of the desired output signal divided by the average absolute value of the input signal. The accuracy of the output signal level is improved by adding a register for setting and a means for correcting the average value of the absolute values of the input signal depending on the type of the register.

【Effect of the invention】

As described above, according to the present invention, it is possible to provide a digital AGC circuit with a simple configuration and improved accuracy in output signal level.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a digital AGC circuit according to an embodiment of the present invention, Fig. 2 is a circuit diagram of a conventional digital AGC circuit, and Fig. 3 is a diagram showing another example of a circuit diagram of a conventional AGC circuit. It is. In the figure, 101, 201... Absolute value unit, 102, 202
．． 303...Averaging device, 103, 105, 204.3
01... Multiplier, 104, 203... Divider, 10
6...Mode setting register, 107...Correction value controller, 302...Squaring unit. Patent Applicant: Canon Co., Ltd. Fig.

Claims (1)

[Claims] a calculation means for calculating the average value of the absolute values of input signals; a setting means for externally setting the type of the input signal; and an absolute value calculated by the calculation means according to the type of input signal set in the setting means. A correction means for correcting the average value of the values to a root mean square value, a division means for dividing a specific set value by the correction value corrected by the correction means, and a quotient of the division result by the division means and input. A digital AGC circuit comprising multiplication means for multiplying signals.