SU1358069A1 - Self-tuning filter - Google Patents

Abstract

The invention relates to radio engineering. The purpose of the invention is to improve the accuracy of filtering signals with an unknown frequency. The self-tuning filter contains search generator 1, phase synchronous filter (SFF) 2, threshold elements 3 and 4, and element 5. At the moment of searching for a signal with an unknown frequency, the device provides for the possibility of suppressing noise. In the absence of a signal at the input, the noise does not pass to the output of a self-tuning filter. When a signal is captured, it passes to the output of the SFF 2. The goal is achieved by introducing the search generator 1 and element 5, and examples of the execution of generator 1 and SFF 2 are given. 1 Il. (L

Description

The invention relates to radio engineering and can be used to receive signals or interference with an unknown frequency, in particular, in the case of impulse and pulse-phase radar navigation systems.

The aim of the invention is to improve the accuracy of filtering signals with an unknown frequency.

The drawing shows a structural electrical circuit of a self-tuning filter,

The self-tuning filter contains search generator 1, phase synchronous filter 2j, first 3 and second 4 threshold elements, first AND 5 o element. Search generator 1 consists of 6 clock pulses generator, Egory element 7, counter 8, Phase synchronous filter 2 contains a generator made in the form of a frequency synthesizer 9, the first 10 and second 11 keys, the first 12 and second 13 low-pass filters, the third 14 and the fourth 15 keys, the adder 16, In addition, the self-tuning filter contains an HE element 17, the third 18 and the fourth 19 elements And,

The self-tuning filter works as follows.

At the initial time, the voltage at the outputs of the first 12 and second 13 low-pass filters synchronously to the phase filter 2 is zero. At the outputs of the first 3 and second 4 threshold elements, a high voltage level is transmitted, which is transmitted through the first And 5 element the input of the second element is And 7, thereby triggering the search generator 1. In this case, the clock pulses from the generator 6 through the open second element And 7 enter the counter 8, each time changing its state by one. At the same time, the frequency of the signal produced by the frequency counter 9 changes discretely with Leo's steps. The volume of the counter 8 is uniquely determined by the number M of tuning steps,

At the output of the frequency synthesizer 9, two digital sequences (meanders) are formed, shifted one relative to the other by a quarter of the period. The sequence from the common-mode output of the frequency synthesizer 9 is fed to the control inputs of the first

0

five

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25

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10 and third 14 keys and from the quadrature output - the second 11. And fourth 15 keys. Until the frequency of the synthesizer 9 is significantly different from the frequency of the input signal, the output voltage of the first 12 and second 13 low-pass filters remains close to zero. This is determined by the frequency response of the synchronous-phase filter 2, which has a narrow frequency band due to the appropriate choice of the time constant of the low-pass filters. At that moment: when the frequency synthesizer frequency 9 becomes equal to the frequency of the input signal at the filter outputs 12 and 13 a low frequency voltage appears that exceeds the threshold level at least in one of the threshold elements 3 and 4. In this case, a low level voltage appears at its output, which through the first element 5 enters the input orogo AND gate 7 is performed stop oscillator 1 search. In this case, the state of the counter corresponds to the code of the input signal frequency, With the output of the first 12 and second 13

30 low-pass filters signals are received respectively on the tr-eti key 14 (in-phase channel) and the fourth. key 15 (quad channel); In the adder 16, the signals are combined — from the in-phase and quadrature channel outputs (not shown). To suppress higher harmonics in the output signal spectrum at the output of the adder l6, the band pass can be turned on.

40 filter o

The self-tuning filter provides for the possibility of suppressing noise at the time of searching for a signal with an unknown frequency.

In the absence of a signal at input 5g, a high level of voltage is converted by an element NOT 17 to a low level, which blocks the third 18 and fourth 19 elements AND, the noise does not pass on. The output of the self adjusting filter When the signal is captured at least at one of the outputs frequency synchronous phase filter 2, a high voltage level appears, which the threshold elements 3 and 4 transform into a low voltage level. "This distance is converted by the element NOT 17 into a high voltage level, which, the third 18 and the fourth 19 elements and, connects the outputs of the frequency synthesizer to the third 14 and fourth 15, and the signal passes to the output of the synchronous-phase filter 2,

5 580694.

Claims (1)

Invention Formula A self-tuning filter containing a synchronous-phase filter and the first and second threshold elements connected to the outputs of the low-pass filters of the synchronous-phase filter, characterized in that, in order to understand the accuracy of filtering signals with an unknown frequency, the sequentially connected first element I was inserted, the inputs of which are connected to the outputs of the first and second threshold elements, and the search generator, the output of which is connected to the control input of the synchronous-phase filter generator. iO 15