SU1350827A1 - Synchronous filter - Google Patents

Abstract

The invention relates to radio engineering. The purpose of the invention is to increase the signal-to-noise ratio. The synchronous filter contains fr keys 2-5, 10-13 and 17-24, capacitors 6-9 and dispenser 14 pulses. When the synchronous filter is operating, each capacitor 6-9 is charged three times to different phases of the input signal, provided that all input signals and the control signal have an initial zero phase and are divided into four equal intervals. The goal is achieved by providing the possibility of suppressing a number of harmonics of the input signal by selecting the time points of an additional charge of capacitors 6-9. The order of charge of capacitors 6–9 and the qualitative assessment of the accumulation values on them of the table. 3 ill. 3 table. (L SO ate oo ti h ti. /

Description

one

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

The aim of the invention is to increase the signal-to-noise ratio.

FIG. 1 shows a structural electrical circuit of a synchronous filter; in fig. 2 - time diagram of voltages in a synchronous filter (a, b, c, d voltage at the input of the synchronous filter frequency f, 2f,

3ft,,; E, e, g, j.

voltage pulse distributor); on -fig. 3 - the spectrum and shape of the output signal with a frequency f,

The synchronous filter contains input resistor 1, input switches 2-5, capacitors 6-9, output switches 10-13, distributor 14 pulses, additional resistors 15 and 16, additional input switches 17-24.

Synchronous filter works as follows.

All input signals and the control signal have an initial zero phase and are divided into four equal intervals corresponding to the switching cycles; then each capacitor is charged three times in different phases of the input signal. This is ensured by the fact that the input keys of the main and additional branches connect each capacitor a maximum of three (not more than N) times to the input signal through the resistors for one period of the main selection frequency, but at different times (phases of the main frequency of the input signal) time Table 14, the order of charge of condensate capacitors and the qualitative assessment of the accumulation of charges on them, are given in Table. 1-3,

In the first variant, charge accumulation on capacitors is performed twice during the main oscillation period (Table 1). The charge estimation is performed by comparing the areas and polarities of the input signals synchronous with the corresponding charging cycles (Fig. 2).

From tab. As can be seen in Fig. 1, the passbands of the synchronous filter will be at frequencies f, and 3f (,. The amplitude spectrum and the output waveform for frequency fp are shown in Figs. Pros, b, respectively. The phase shift is in 1350827. 2

the input voltage is due to the difference in time between the accumulation and the reading of the signal.

In the second variant, the input signals pass through the proposed synchronous filter, provided that the times of connection of the capacitors for charge to the input signal correspond to the cycles of the table. 2, The capacitor charge is made twice during the main oscillation period.

From tab. 2 based on graphical output. Who analysis (Fig. 2) shows that

J5 input signals of frequency f, 3fo and 4fo do not pass through the synchronous filter to the output. At the output of the synchronous filter there is only one frequency 2f.

20 In the third embodiment, the capacitors are charged three times (N-1) during the period of the main oscillation (Fig. 2) at the times of connecting the capacitors to the input circuit.

25 respectively table. 3,

From tab. 3, it can be seen that in this case, signals of a frequency of .f, 30 2f, and 3f, are present at the output of the synchronous filter.

A synchronous filter allows you to accumulate signals on at least two capacitors at the same time and form a given frequency response by the formula

Nn - | 2. i, .j.

K (---- N) / ,, | :, /,

40

where j. is the minimum unit; i is the summation index; N is the number of capacitors on which the input signal is simultaneously accumulated; dN - phase shift; n is the harmonic number. Thus, by selecting the time points of the additional charge 50 of the capacitors, it is possible to suppress a number of harmonics of the input signal, which allows an increase in the signal-to-noise ratio,

Claims (1)

gg Formula A synchronous filter containing an input resistor, the output of which is connected to the combined inputs of N to N-N - | 2. i, .j. K (---- N) / ,, | :, /, where j. is the minimum unit; i is the summation index; N is the number of capacitors on which the input signal is simultaneously accumulated; dN - phase shift; n is the harmonic number. Thus, by choosing the time points of an additional charge of capacitors, it is possible to suppress a number of harmonics of the input signal, which allows an increase in the signal-to-noise ratio, The formula is A synchronous filter containing an input resistor, the output of which is connected to the combined inputs of N ce313 Drink, each of which consists of serially connected input and output keys, the connection point of which is connected via a capacitor to the common bus, and the outputs of the output keys are combined and are the output of the synchronous filter, as well as the pulse distributor, the outputs of which are connected to the control inputs corresponding keys, characterized in that, in order to increase the signal-to-noise ratio, N-1 resistors are inserted, the first terminals 6 7 which are connected and connected to the input of a synchronous filter, and NI additional input keys are entered into each of the N circuits, the outputs of which are combined and connected to the output of the input key, and the inputs are additional inputs of the circuits and connected to the other terminals of the corresponding additional N-1 resistors, at the same time, the control inputs of additional N-1 input keys are connected to the corresponding of the N outputs of the pulse distributor. Table 1 table 2 No Yes No No eleven t, t. it Table 3 There is there is no S 3fo A L G l1 / K / I fo fo fo Well FIG. 2 7 it ff 6 t, r f Compiled by Y. Chernyshov. Editor L. Gratilo. Tehred M-Khodanych CorrectorN. King Order 5298/57 Circulation 900 Subscription. VNIIPI USSR State Committee for inventions and discoveries 1 13035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, st. Project, 4