SU1626329A1 - Automatic gain control device - Google Patents

Abstract

The invention relates to radio engineering and can be used in receiving and transmitting devices. The aim of the invention is to improve the accuracy. The automatic adjustment device contains an adjustable quadrupole 1, a high-frequency amplifier 2, an amplitude detector 3, a two-threshold comparator 4, a switch 5, a reversing counter 6, a decoder 7, a code conversion unit 8 from n to unitary, a block of 9 optocouplers, a 10-clock generator, a block 11 variable resistors, a block of 12 transistor switches, a source of voltage 13, an inverter, signal emitters, first and second resistors and photodetectors. Use of block 9 of the optocoupler as an element of galvanic isolation and isolate ovannogo voltage source 13 is used to control supply unit 12, transistor switches, avoids the base currents of transistor switches controlled quadripole circuit upravpeni 1 February yl. (Ls

Description

o you

| 0

s

.go

I4d

FIA.1

The invention relates to radio engineering and can be applied in receiving and transmitting devices.

The aim of the invention is to improve the accuracy.

FIG. Figure 1 shows the electrical structure of the automatic gain control device; in fig. 2 is the electrical circuit diagram of some blocks of the automatic gain control device.

The automatic gain control device contains an adjustable quadrupole 1, a high-frequency amplifier 2, an amplitude detector 3, a two-threshold comparator A, a switch 5, a reversible counter 6, a decoder 7, a code conversion unit 8 from n to unitary, a block 9 op topar 10 clock generator, a variable resistor unit 11, a transistor switch unit 12, a voltage source 13, an inverter 14, light emitters 15, first resistors 16, photodetectors 17, and second resistors 18.

The device works as follows

In the initial state, the signal from the output of the regulated quadrupole 1 through the high-frequency amplifier 2 is fed to the input of the amplitude detector 3 and after detection in the form of a constant voltage is fed to the input of the two-threshold comparator 4. With the value of the adjustable signal Ug Ho (Ho2 and Xgl are the reference voltages a two-threshold comparator 4) the signal d -I opens switch 5 and connects the generator 10 clock pulses to the addition input of the reversible counter 6. As a result, the reversible counter b is filled in proportion to the time the existence of Ug Xoa values. The number of pulses arriving at the reversal counter 6, in the form of a binary code at its output, is fed to the decoder 7. In the initial state, all its outputs have a positive potential, which being converted in the code 1 conversion unit 8 from n to unitary, excites LEDs optocoupler unit 9 and captures the photodetector 17 (phototransistor) in the saturation mode. As a result, current from the positive pole of the voltage source 13 flows through said photodetectors and their resistors 18. Consequently, in the saturated state, the photodetectors 1, by their low resistance, shunt the base-emitter junctions of the transistor switches of the block 12, as a result of which the latter remain closed and control

the signal does not go to the adjustable quadrupole 1.

As soon as the binary code (as mentioned above) arrives at the input of the decoder 7 from its output, the number of which corresponds to the incoming number, the potential command (in our case, a logical zero, log O) goes to one of the inputs of the conversion unit 8. Invert the log twice. ABOUT

0 interrupts the drive mode of the LED of the corresponding optocoupler of block 9, with the result that the photodetector (phototransistor) of this optocoupler is brought out of saturation mode, switches to a high resistance state and stops shunting the base-emitter section of the transistor switch of the block 12. Control voltage of block 13 now acts between the base and the emitter of the transistor

0 key, providing current saturation of this key and putting it into the Open state. The specified current is closed in an autonomous circuit formed between the positive and negative poles.

5 sources 13 voltages. This makes it possible to realize isolation between the collector and base currents of the transistor switch, as a result of which the magnitude of the transmission coefficient of the regulated quadrupole

0 is set only by the collector current of the key, while the base current does not fall on the control input of the adjustable quadrupole, which leads to an increase in the control accuracy.

5 Upon receipt of a fourfold one

binary code 0001 decoder 7 generates a signal log. About to the first input of block 8. From the output of the lower bit of block 8, the signal log. 1 is fed to the input of the inverter 14,

0 again converted to a signal log. O. As a result of the excitation of light by the emitter 15 of the corresponding optocoupler of block 9, the optocouplers stop and the photodetector 17 goes out of saturation mode, the transition to the mode

5 cutoffs. The corresponding key of the transistor switch unit 12 is opened, providing a predetermined sampling of the control current of the adjustable quadrupole 1.

If the input of the decoder 7 enters

0 code 0010, then from its second output to the input of the second bit of conversion unit 8, the signal O is received instead of 1 in the initial state. The specified dvadzhy signal is inverted in the form of a log. Oh comes on

5, the input of the optocoupler unit 9, in connection with which the excitation of the light emitter 15 of this optocoupler stops, the photodetector 17 switches to a high resistance mode, and therefore a transistor switch of the second sampling opens. Through the open key, the current enters the load. The amount of current switched by each key is adjusted using resistors of a block of 11 variable resistors. At the same time, the signal O from the output of the inverter 14 interrupts the excitation of the opto-pair corresponding to the light emitter 15, in connection with which, similarly to the previously described, the transistor switch of the first sampling turns on.

Thus, the current of both keys flows through the load. The magnitude of the current of both switches is determined by the resistors of the block 11 and the voltage from the bias source Eo

The voltage source 13 can be made on the basis of a constant-voltage converter into a constant as a serial connection of a constant-voltage-to-AC converter, a transformer, a rectifier and a filter, where the transformer plays the role of an isolating element.

Claims (1)

Claims An automatic gain control device comprising a series-connected adjustable quadrupole, to the control input of which is connected an output of a transistor switch unit, a high-frequency amplifier, an amplitude detector, and a two-threshold comparator, a series-connected reversible counter, a decoder, and a code 1 conversion unit from n to unitary, serially connected clock generator and switch, the control input of which is connected to the output of a two-threshold computer Ator, and first and second outputs are connected to inputs of the addition and subtracting a reversible counter as well as a block of variable resistors, some of the resistor outputs are combined and are the input for supplying the bias voltage, and other resistor terminals, which are outputs of the variable resistor block, are connected to the collectors of transistors of the transistor switches, the emitters of which are combined and the output of the transistor switch unit, wherein the inputs of the presetting of the reversible counter are inputs for supplying an installation code, characterized in that, in order to improve accuracy, it is entered by an inverter, an optocoupler unit, and a voltage source, the output of the first discrete block of the conversion code 1 from n to unitary is connected via an inverter, and the outputs of the remaining discretes are connected directly to the inputs of the optocoupler unit, the outputs of which are connected to the control inputs of the transistor switch unit, This optocoupler unit is made in the form of light emitters, some of the outputs of which are the inputs of the optocoupler unit, while others are connected through the first resistors to the common bus of photodetectors, the first conclusions of which are the outputs of the The optocoupler and the second resistors, each of which is connected to the first output of the corresponding photodetector by one output, and their other outputs are one of the power inputs of the optocoupler unit, the second outputs of the photodetectors are another input power supply of the optocoupler unit, also connected to the output of the transistor switch unit, and the outputs of the voltage source are connected to the power inputs of the optocoupler unit I