SU915220A1 - Regulator for automatic gain control - Google Patents

Description

The invention relates to radio engineering and can be used in the main receiving devices literal printing.

Known regulator for automatic gain control (AGC), containing a limiter and series-connected comparison unit with a threshold and drive [13.

However, the known device has insufficient noise immunity.

The purpose of the invention is to improve the noise immunity when receiving telegraph signals.

To do this, in the regulator for automatic gain control (AGC), containing a limiter and a series-connected comparison unit with a threshold and a drive, serially connected telegraph distortion meter and a digital-to-analog converter are connected between the limiter and the comparison unit with a threshold.

Figure 1 shows the structural electrical circuit of the regulator used in the radio; figure 2 - diagrams explaining the operation of the device.

The device contains a limiter; 1, made in the form of a trigger, drive 2, meter 3 telegraph

distortion, digital-to-analog converter (DAC) 4, block 5 comparison with

5 threshold, as well as the object of regulation, which includes the input and adjustable stages 6 and 7 of the receiver.

The device works as follows.

Yu. Figure 2a shows a random fragment of the information signal at the output of receiver limiter 1, and figure 26 shows the possible nature of the time dependence of the telegraph size. _ Noise distortion of the echo signal. This dependence is random, as it is determined by the level of the useful signal, the levels, the number and frequencies of the input ’noise at 20 and other factors.

On figv shows a diagram

signal * at the output of the DAC 4. The dotted line parallel to the time axis on FG. 2c, characterizes the level of telegraph distortion at which

²⁵ the block 5 of the comparison with the threshold is triggered.

With a negative potential at the output of block 5 (fig.2g), drive 2 produces an upward control voltage branch and an attenuation increase of 3

915220

four

distortions will fluctuate around its threshold value, and the control voltage of drive 2 and the degree of attenuation - around a certain value determined by the level of the useful signal, as well as the number, location on the frequency axis and the intensity of interference.

The signal at the input of the meter is 3 telegraph distortions, i.e. signal on. The output of receiver limiter 1 is a sequence of constant amplitude pulses with steep edges. Pulse distortion (edge, telegraph distortion) is determined by the ratio of signals and interference. When changing the gain of the adjustable stages 7 (using the AGC system), the amplitude at the output of the limiter 1 does not change, only the pulse duration changes (telegraph distortion).

Thus, the proposed device with any excess level of the useful signal in excess of that required to obtain the specified telegraph distortion will reduce the gain of the broadband path, i.e. increase the linearity of the receiver, which, in turn, will increase the tolerance of reception.

lichivaetsya (figd). With a positive potential at the output of block 5 (when telegraphic distortion exceeds the threshold level) the output voltage and the degree of attenuation decreases.

The phenomena described occur in the device when the control ring is open. When the AGC circuit is closed, the processes proceed differently. The further description of the processes corresponds to the case when the AGC circuit is closed, the value of the telegraph distortion at the initial moment of regulation is less than its threshold value. The level of the useful signal at the receiver input exceeds its threshold sensitivity, and the distortion of the useful signal is caused by interference of nonlinear origin. In this case, the drive 2 generates an ascending 20 branch of the control voltage, the attenuation increases, and the telegraph distortion (Fig. 2e) decreases as compared with the case corresponding to an open AGC ring. The reduction of distortions due to the varying degree of influence of attenuation on the useful signal and non-linear disturbances will continue until the signal level decreases to such an extent that its (signal) will begin to distort the receiver's own noises (signal level is comparable to the threshold receiver sensitivity), After that, the telegraph distortion with increasing attenuation will begin to increase. At that point in time, when the level of telegraphic distortion exceeds the limit value (Figure 2e, dashed line), unit 5 changes the polarity of the output voltage, drive 2 begins to generate a downward control voltage branch and attenuation begins to decrease. When telegraphic distortion decreases, block 5 will work again - the control voltage of drive 2 and the attenuation level will start to increase, etc.

As can be seen from Fig.2zh, in the steady state the value of the telegraph

Claims (1)

Claim 35 Regulator for automatic gain control (AGC), containing a limiter and a series-connected comparison unit with a threshold and a drive that differs from me in order to increase noise immunity when receiving telegraphic signals, series-connected telegraph meters are inserted between the limiter and the comparison unit with a threshold distortion and 45 digital-to-analog converter.