RU1786601C - Method of determination of frequencies of natural oscillations of coil ends of stator winding of electric machine - Google Patents

Abstract

Usage: receiving frequency-manipulated signals in transmission systems of discrete information. SUMMARY OF THE INVENTION: the receiver comprises mixers 1 and 2, a high-frequency oscillator 3, a phase shifter 4, low-pass filters 5 and 6, limiters 7 and 8. a decision block 9, a decoder 10, 1, an analyzer 11 for the presence of a signal. An increase in noise immunity is achieved by protecting against errors of the first kind due to the prohibition of decoding the output signal commands in the absence of a signal, a frequency-manipulated information carrier stream at the input. The receiver may be characterized by the presence of a signal analyzer 11. 1 s.p. f-ly, 3 silt,

Description

ate

WITH

XI 00 Oh Oh 00 Oh

The invention relates to communications and can be used in discrete information transmission systems for receiving frequency-shifted (FMN) signals, for example, in call systems.

A FMN signal receiver is known, comprising a high frequency (HF) mixer, a high frequency controlled oscillator, a low frequency (LF) generator, a delay line, a first low-pass filter (LPF), a frequency conversion unit, a phase discriminator, a second low-pass filter and a limiter.

In the known receiver, if the frequency of the RF generator is unstable, in order to ensure the operability of the receiver of the FMN signals, it is necessary to expand the bandwidth of the first low-pass filter, which will lead to a decrease in the signal-to-noise ratio at the input of the phase discriminator and, therefore, to a decrease in the noise immunity of the known receiver of FMN signals.

The closest in technical essence to the claimed is the receiver of the FSK signals, containing two mixers, a phase shifter, an RF generator. two filters, two limiters, a deciding unit and a decoder. The first inputs of the mixers are interconnected and made by the input of the receiver, the output of the RF generator is connected to the second inputs of the mixers, and directly to one of them and through the phase shifter, the output of each mixer is connected to the input of the corresponding low-pass filter, the outputs of which are connected to the inputs of the corresponding limiters, the inputs of the deciding unit are connected to the outputs of the limiters, the output of the deciding unit is connected to the input of the decoder, the output of which is made by the output of the receiver.

A disadvantage of the known FMK signal receiver is low noise immunity due to the lack of protection of the receiver from errors of the first kind (false alarm) when an erroneous decision is made whether there is a signal that arises as a result. that noise is taken as a signal.

The aim of the invention is to increase the noise immunity of the known receiver of FSK signals by introducing protection from errors of the first kind by prohibiting the decoder from decrypting the output signal of the decision block in the absence of a signal, which is frequency-manipulated by the information stream of the carrier at the receiver input.

The goal is achieved in that the receiver is frequency-shift keyed

signal comprising a first mixer, the first input of which is the input of the receiver and connected to the first input of the second mixer, to the second input of which

the output of the phase shifter is connected, the input of which is connected to the output of the high-frequency generator and to the second input of the first mixer, the output of which and the output of the second mixer are connected respectively to

0 inputs of the first and second low-pass filters, the outputs of which are connected respectively to the inputs of the first and second limiters, the outputs of which are connected to the inputs of the deciding unit, the first output of which is connected to the first input of the decoder, a signal presence analyzer, the first, second and third inputs and the output of which is connected respectively to the outputs of the first and second limiters, with

0 by the second output of the decision block and with the second input of the decoder, the output of which is the output of the receiver.

In addition, the signal analyzer contains series-connected

5. a sign control unit, a phase comparator, a low-pass filter, a comparison unit and a key unit, the second input of which is connected to the first input of the sign control unit, whose second input and second input

0, the phase comparator are respectively the first and second inputs of the analyzer, the third input and output of which are the first input of the sign control unit and the output of the key unit, respectively.

5 The constructive implementation of the receiver of the FSK signals according to the invention with the introduction of a signal presence analyzer made it possible to increase the noise immunity of the receiver, since decryption of the video signal

0 of the block by the decoder and the formation of the output signal of the receiver is carried out only in the presence of a frequency-manipulated information stream carrier at its input. Then regardless of structure

5 of the modulating digital stream, the signals at the inputs of the phase comparator in the signal analyzer mainly have a constant phase shift of 90 °, which changes for a short time, not exceeding

0 period of the frequency of deviation, at the time of changing the sign of the information package to the opposite. In this case, the output signal of the phase comparator, filtered by a low-pass filter, exceeds the comparison threshold of the comparison circuit and holds the key circuit in the open state, passing through it the video signal of the decoding unit to the decoder input. In the absence of a carrier signal and the presence of only a noise signal at the receiver input, the output signal of the decision unit does not pass to the decoder, since the phase shift of the signals at the inputs of the phase comparator changes randomly. Then the output signal of the phase comparator, filtered by a low-pass filter, below the comparison threshold and the comparison circuit keep the key circuit closed, without passing through it the video signal of the decoding unit to the decoder input. This provides protection against errors of the first kind (false alarm), since the false commands (false alarms) that are acquired by the deciding unit from the noise signal do not enter the command decoder.

In FIG. 1 is a structural functional diagram of a claimed receiver of FSK signals; in FIG. 2 is a structural functional diagram of a signal presence analyzer in a receiver; in FIG. 3 timing diagrams illustrating the operation of the receiver in a particular embodiment.

The receiver of the FSK signals contains the first 1 and second 2 mixers, an RF generator 3, a phase shifter 4, a first 5 and a second 6 low-pass filters (low-pass filters), the first 7 and second 8 limiters, a deciding unit 9, a decoder 10 and a signal presence analyzer 11 (see Fig. 1). The first input of the first mixer

I is the input of the receiver and is connected to the first input of the second mixer 2, to the second input of which the output of the phase shifter 4 is connected, the input of which is connected to the output of the RF generator 3 and to the second input of the first mixer 1, the output of which and the output of the second mixer 2 are connected respectively to the inputs of the first 5 and second 6 low-pass filters, the outputs of which are connected respectively to the inputs of the first 7 and second 8 limiters, the outputs of which are connected to the inputs of the deciding unit 9, the first output of which is connected to the first input of the decoder 10, and the first, second and third inputs and output of the analyzer

II, the presence of a signal is connected respectively to the outputs of the first 7 and second 8 limiters, with the second output of the deciding unit 9 and the second input of the decoder 10, the output of which is the output of the receiver.

The decision unit 9 comprises a phase detector 12 and a clock synchronization unit 13 (see Fig. 2).

The first input of the phase detector 12 is made by the first input of the decision block 9, and the second input of the phase detector 12 is the second input of the decision block 9. The output of the phase detector 12 is connected to the input of the clock synchronization block 13 and is made the second output of the decision block 9, the output of the clock block 13 synchronization is performed by the first output of the decision block 9.

The signal presence analyzer 11 comprises a phase comparator 14, a sign control unit 15, a low-pass filter 16, a comparison unit 17 and a key unit 18 (see Fig. 2).

The second input of the key unit 18 is connected to the first input of the control unit by the sign 15, the second input of which and the second input of the phase comparator 14 are respectively the first and second inputs of the analyzer, the third input and output of which are the first input of the control unit by the sign 15 and the output of the key unit eighteen.

The receiver of the FSK signals operates as follows.

The RF generator 3 (see Fig. 1) produces a signal of the following form

Si (t) COs ((Wrt + pg), (1)

where Ok is the frequency of the signal of the generator 3;

(rg is the initial phase of the signal of the generator 3.

The signal Si (t) oT of the RF generator 3 is fed to the input of the phase shifter 4, the output of which receives the signal Si1 (t) shifted by 90 ° with respect to the signal Si (t) of the form

Sl (t) -sin ("rt + (pg).. (2)

The signals Si1 (t) from the output of the phase shifter 4 and Si (t) from the output of the RF generator 3 are respectively supplied to the second inputs of the second 2 and first 1 mixers, the first input of which receives the received signal of the form

S2 (t) cos (wv, t H- ai t + p2}, (3) where co0 is the central frequency of the received signal;

a - ti depending on what is transmitted:

logical 1 or

rg is the initial phase of the received FSK signal;

Asod 2; rAfg - frequency of deviation of the received signal.

At the outputs of the first 5 and second 6 low-pass filters, which serve to suppress high-frequency conversion products, taking into account the assumption (signals ik and pi

S3 (t) cos (aj Awgt),

$ 4 (t) sin (ai Aftjg t) (4)

As a result, at the output of the first 5 and second 6 filters at, i.e. if logical 1 is received, the signals Sj (t) and (t) will have the form

S3,, 1 (t) cos Awgt

84 1 (t) sin Awgt .. (5)