SU1133658A2 - Synchronous filter - Google Patents

Abstract

SYNCHRONOUS FILTER St. 881988, about. in order to reduce intersymbol interference when receiving periodic and non-periodic pulses, a smoothing filter and a third key are inserted, connected in parallel and connected between the output of the first key and the common bus, the pulse counter and the element And connected to the second additional output of the control unit: and to the input of the pulse counter, as well as an additional key is inserted into each branch, connected in parallel with the switched key, with the output of the AND element It is single with the setup input of the pulse counter, with the control inputs of the second and third keys, and with the control inputs of the additional keys in each branch.

Description

The invention relates to radio engineering and can be used in frequency selection devices.

According to the main auth. No. 881988 is known a synchronous filter, containing a series-connected integrating circuit, an amplifier, a first key and N parallel branches, each of which consists of a series-connected capacitor and a switched key, and one terminals of the capacitors of all branches are combined, the second branches of the switched keys of all branches are connected to a common bus, as well as a second key, connected between the output of the integrating circuit and the point of connection of the capacitors, and a control unit, the control inputs of all switched branches connected to the control module's output outputs, and the control inputs of the first and second keys are connected to the first additional output of the control unit, and the control input of the first key directly, and the second through HtisepTop (1 j.

However, the known synchronous filter has a narrow bandwidth, has a high quality factor, which leads to the fact that when receiving non-periodic radio pulses (a sequence of pulses with high-frequency filling) the filter rings and the ringing time and separation of pulses becomes impossible, i.e. intersymbol interference appears Reducing intersymbol interference due to bandwidth expansion leads to poor filtering quality, and the synchronous filter loses its advantages over the others.

The goals of the invention are to reduce intersymbol interference when receiving periodic and non-periodic radio pulses.

The goal is achieved by the fact that a synchronous filter containing a series-connected integrating circuit, an amplifier, a first switch and N parallel branches, each of which consists of a series-connected capacitor and a switchable key, all of the terminals of the capacitors of all the branches being combined, the second terminals of the switched the keys of all branches are connected to the common bus, as well as the second key, connected between the output of the integrating circuit and the connection point of the capacitors, and the control unit, and the control inputs of the switched the keys of all branches are connected to the corresponding outputs of the control unit, and the control inputs of the first and second keys are connected to the first additional output of the control unit, and the control input of the first key is directly and the second through the inverter, a smoothing filter and a third key are additionally connected parallel and connected between the output of the first key and the common length, the series-connected counter and the element I, the other input of which is connected to the second additional output of the control unit and to the input m pulse counter, and in each branch introduced an additional key, a dial key is connected in parallel, the output of AND gate is connected to the adjusting input of a pulse counter, with the control inputs of the second and third keys and with the control inputs of the additional keys in each branch.

The drawing shows a structural electrical circuit of a synchronous filter.

The synchronous filter contains an integrating circuit 1, an amplifier 2, a first switch 3, a second switch 4, an inverter 5, N parallel branches, each of which consists of a capacitor 6-1, 6-2, ..., 6-N, switch key 7 -1, 7-2, ..., 7-N, control block 8, pulse counter 9, And 10 element, N additional keys 11-1, 1.1-2, .., 11-N, third key 12, as well as a smoothing filter 13.

Integrating circuit 1 may, for example, contain an input resistor and an integrating circuit capacitor connected between the input of the synchronous filter and the common bus, with the common point of the resistor and the capacitor of the integrating circuit being connected to the input of the amplifier 2.

Control unit 8 represents, for example, a sequentially coherent clock pulse generator and a ring pulse distributor. The frequency of the clock generator is N times the frequency of filling the radio pulses. The ring distributor has N outputs, as well as a second additional output from which an N-pulse is fed to the counter 9. The synchronous filter operates as follows. At time t; From the second output of the control unit 8, a pulse arrives at the control input of the switched key 7-1 of the i-th branch, opening this switched key 7-i for some time. In this case, the capacitor 6-i through the amplifier 2 and the open first key 3 receives a portion of the charge from the input signal through the input resistor of the integrating HfenH 1. At the end of the time ui, the switched key 7-i is closed and the charge circuit of the capacitor 6- is broken. The capacitor 6-i remembers the charge it received. At subsequent times tj. , and t-C, capacitors 6-i of other branches receive portions of charge from other parts of the signal period and also memorize them. After the period of the input signal, the considered capacitor 6-i is again connected to the input signal and receives a new portion of the charge, etc., i.e. capacitors 6-1 -6-N remember the received charge portions from separate parts of the input signal period. The same charge portions from all parts of the signal period receive only one integrator circuit capacitor 1 through the input resistor. At the i-th instant of time, the capacitor of the integrating circuit 1 receives a portion of the charge and through amplifier 2 and the open first switch 3 transfers it to the co-receiver 6-i (with open switched key 7-i). Then, the switched key 7-i is closed, the circuit of the capacitor 6-i is broken, and it stores the resulting charge. After the period of the input signal T, from the i -th time point, i.e. at the moment of time, the voltage across the capacitor of the integrating circuit 1 is not equal to that which was on it at the moment. -tj, since it received portions of charge from other parts of the signal period. But dp normal operation of the synchronous filter is necessary that the time until the circuit of the capacitor 6-i is broken, i.e. through the period of the input signal T, before the next switching-on of the capacitor 6-i, the charge on the capacitor of the integrating circuit 1 would be equal to the charge on the capacitor 6-1. Therefore, the charge on the air conditioner. Integrating circuit 1 before switching on the capacitor 6-i must be restored. For this, a second switch A is used, which is switched on for a short time, and the voltage from the capacitor. 6-i is transmitted to the capacitor of the integrating circuit 1. A similar process occurs when the remaining 6-1-6-N capacitors are switched on. At the same time, integrating circuit 1 operates as a combination of several synchronous filters. However, at the end of the input signal, the charge transfer process from the capacitors 6-i to the capacitor of the integrating circuit 1 and back continues for a long time due to the presence of a constant time input and output circuits of the synchronous filter. Therefore, at the output of a synchronous filter for a long time, there will be a gradually decreasing response to the terminating input signal and, if the duration of the pause. between adjacent radio pulses (input signals) is small, to separate these signals after the filter becomes impossible due to the ringing of the filter. The elimination of the ping of the filter is as follows. At the second additional output of the control unit 8, after each period of the input signal, a pulse appears, which is recorded in the counter 9. When the counter 9 is filled, the potential from its output goes to the first input of the And 10 element and after the next additional pulse from the second additional output of the block 8 control at the output of the element And 10 a pulse appears, which opens for a short time additional keys 11-1 to 11-N, second key 4 and third key 12, and also zeroed the counter 9. Capacitors 6-1 to 6-N, as well as the capacitor of the integrating circuit 1 at the same time, the response to the input signal at the output of fn. disappears. The filter is ready to receive the newly received input signal, and when a new radio pulse arrives, the process repeats I, I K, to the counter 9 is selected

Claims (1)

SYNCHRONOUS FILTER according to ed. 881988, about. It differs in that, in order to reduce intersymbol interference when receiving periodic and non-periodic radio pulses, a smoothing filter and a third key are introduced, connected in parallel and connected between the output of the first key and the common bus, the pulse counter and the element And, the other input of which is connected to the second additional output of the control unit and with the input of the pulse counter, as well as in each branch, an additional key is inserted, connected in parallel with the switched key, and the output of the element And connection n a mounting input pulse counter, to the control inputs of the second and third keys and to control inputs of the additional keys in each branch.