SU489200A1 - Automatic gain control device - Google Patents

Description

This invention relates to radio and may be used in professional radio receivers. A device for automatic gain control is known, which contains an adjustable path that includes a discrete attenuator, the control inputs of which are connected to the corresponding outputs of a control voltage converter. However, the known device has not enough high accuracy, stability, and not enough wide dynamic range of adjustment. The purpose of the invention is to increase accuracy, stability and expansion of the dynamic range of adjustment. This is achieved by introducing a smooth attenuator into the regulated path, the control input of which is connected to an additional output of a control voltage converter made in the form of series-connected AND differential amplifiers, where I is the number of stages of the discrete attenuator, and the second input of each differential amplifier is connected with the first through a discriminator level with an additional output, which is one of the main outputs of said converter. The drawing shows a functional1 — the scheme of the device for automatic gain control (AGC) contains an adjustable path 1 with discrete attenuator 2 and a smooth attenuator 3, i control voltage converter 4, consisting of discriminators 5, 6: And 7, made according to the scheme of non-symmetric trigger, and are connected in series by the jibix differential amplifiers 8, 9 and JO The output of the adjustable path 1 is connected to the input of the converter and the control voltage via a serially connected AGC detector 11 and an AGC filter 12. The control inputs of the diffle attenuator 2 are connected to the main outputs of the converter 4 of the control voltage by the additional outputs of the discriminator 5, 6, Level 7). In each differential amplifier 8, 9 and 10, the first input is connected to the input, and the second input to the output of the discriminators 5, 6, and 7 up-g is, respectively. An additional output of the control voltage converter 4 (the output of the differential amplifier 10 is connected to the control input of the smooth

attenuator 3.

The device works as follows. .

The change in the output voltage of the regulated path 1 within the allowable limits corresponds to the exchanged control voltage at the output of the AGC filter 12 (the input of the control voltage converter 4) from zero to the highest value.

The voltage at each output of any discriminator 5, 6, or 7 takes two fixed values depending on its state, with the output voltage connected to the input of the differential amplifier 8, 9, 10, respectively,: in the initial (unworked state is zero, and in the driven state - half the maximum value of the control voltage at the output of the AGC filter 12. The voltage of the main outputs, control voltage converter 4 (at the additional outputs of discriminators 5, 6. and 7) are Acheni, in which the inclusion of the discrete attenuator U steps occurs only in the activated combination of dis: to iminators;

In the absence of a control voltage at the output of the AGC filter 12, the discriminators 5, 6 and 7 are in the initial state, the voltages at the inputs and outputs of the differential amplifiers 8, 9 and 1 are even zero, therefore, the adjustable path 1 has the highest gain .

When a control voltage is applied to the output of the AGC filter, it is amplified by series-connected differential amplifiers 8, 9 and 10, with each amplifier subtracting the voltage supplied from level 5, 6 and 7 to the second input from the control voltage applied to the first input, and the differential voltage gain 2 times. The amplified control voltage from the auxiliary output of the control voltage converter 4 is supplied to the control input of the main attenuator 3, the transmission coefficient of which, and, consequently, ps.

regulated tract 1 diminution. When the control voltage at the output of the AGC filter reaches the following value: when the coil voltage at the input of the discriminator level 7 and in the first input of the differential amplifier 10 is equal to half the maximum value of this control voltage, the discriminator level 7 activates, turning on the corresponding level discrete attenuator, and will output a voltage of 10 to the second input of the differential amplifier, equal to half the highest control voltage at the output of the AGC filter 12. The output voltage is the differential th amplifier 10 falls to zero and AEO (IRC 34; ent smooth transmission attenuator 3 increases abruptly to the initial value When this gain controlled path 1 before and after actuation of the discriminator 7 omenta same level..

With a further increase in the control voltage at the output of the AGC filter 12, the voltage on the differential amplifier 10 will increase from zero to the highest value of the control: Shego voltage at the output of the AGC filter, at which the voltage at the discriminator input reaches the voltage level married srabatan. A discriminator level 6 will work, causing the corresponding level of discrete attenuator 2 to turn on, the voltage at the output of the differential amplifier r 9 will be reduced to zero, the discriminator 7 level will be reset to its original state, the discrete attenuator stage 2 will be turned off and the voltage will decrease ;; control on the control of the input of the smooth attenuator down to zero. A further increase in the control voltage at the output of the AGC filter 12 will lead to an increase in the voltage at the control input of the Avalan attenuator 3 from zero to the highest value of the control voltage at the output of the AGC filter 12, with a rotor; It is obvious that the discriminator 7 of the level will be triggered and the corresponding step of the discrete attenuator 2 will be activated. Similarly, the device operates with a further increase in the control voltage at the output of the AGC filter 12. When its maximum value is reached, all the level discriminators will be in the activated state, the voltage on the control input of the soft attenuator 3 will be equal to the maximum control voltage at the output of the AGC filter 12 and, smoothly, the gain of the controlled

Truck A and 1 will have the least termination:

Decreasing the control voltage at the output of the AGC filter 12, the voltage at the control input; soft attenuator 3 will decrease, increasing the gain of the regulated path 1 until the discriminator of the i-level returns to the initial state, {OFF the associated attenuator stage 2 and outputting the voltage 10 to the input of the differential amplifier 10 (equal to zero, which leads to an increase in the voltage at the control input of the plasma attenuator 3 to a value equal to the higher value of the control voltage | Neither the AGC filter output 12. A further decrease in the control voltage will lead to su discriminator b. level to the initial state and work; Niyu discriminator 7 level, etc. until | discriminators 5, 6 and 7 I level go to the initial state, I and the voltage at the control input of the smooth Attenuator 3 will not become zero, which corresponds to the greatest gain of the adjustable path 1 and zero voltage at the output of the AGC filter 12.

Thus, when the control voltage on the output of the AGC filter 12 changes from zero to the highest value of and; on: the revolution, the voltage at the control input of the soft attenuator 3 changes within the same range as many times as gtr. the gain of the adjustable path 1 varies monoHITHO within selected limits.

Subject invention

An automatic gain control device containing an adjustable path includes a discrete attenuator, the control inputs of which are connected to the corresponding outputs of the control voltage converter, characterized in that, with a whole increase in the accuracy, stability and expansion of the dynamic range of the control, entered into the regulated path: a smooth attenuator, the control input of the kojtoporo is connected to the auxiliary output of the control converter 1, made in the form of a successive connector nennyh it- differential Wuxi | lnteley, where n - the number of discrete steps;. Nogo attenuator, said second input of each differential amplifier is connected to the first through the discriminator level s; an additional output, which is one of the main outputs of the said transducer.

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