SU1392627A1 - Frequency telegraphy signal demodulator - Google Patents

Abstract

The invention relates to communication technology. The purpose of the invention is to improve noise immunity. The demodulator contains a phase detector 1, a low-pass filter 3, an adjustable oscillator (PG) 8. To increase the noise immunity, an amplitude comparator 4, a delay block 5, two polarity switches 2, 6 are introduced in the device, providing high-speed frequency tuning of the PG after for information manipulation of the demodulator input signal frequency. Introduction to the device of block 9 for the search and fixation of the phase mismatch in synchronous mode allows for high noise immunity. 1 hp f-ly., 1 ill.

Description

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H: u fipPTeHHR refers to a technique of communication and may use radio systems to receive frequency telegraphy signals.

The purpose of the invention is to increase the noise immunity of

The drawing shows a structural electrical circuit of the proposed demodulator.,

The demodulator contains a phase detector 1, a first polarity switch 2, a low pass filter 3, an amplitude comparator 4, a delay block 5, a second polar compressor 6, an adder 7, an adjustable oscillator 8, a phase mismatch search and fixation unit 9, the state is PI from the first ft of 10 low frequencies, the source 11 of the reference voltage, the amplitude comparator 12, the generator 13 of the counting pulses, the reversing counter 1A, the digital-analogue converter 15 and the second low pass filter 16,

The demodulator works as follows.

In the absence of a demodulator input signal, the Zero voltage is applied to the input of the block 9 for searching and fixing the phase mismatch, the reversible counter 14 is turned on in one direction, and the output of the block 9 forms a continuously repetitive linear voltage, which through the sugmator 7 modulates the frequency of the tunable generator 8 , thus performing a search for the input signal of the demodulator by frequency, c. The frequency range and the tuning rate of the tunable oscillator 8 are determined by the magnitude of the output voltage. voltage digital to analog converter 15 and the pulse repetition frequency from the output of the generator 13, respectively of

When a signal appears at the input 17 of the demodulator at the output of the phase detector 1, a beating voltage appears with a linearly variable frequency. Amplitude comparator 4 together with the switch 2 of the polarity rectifies f pulses with beats. the input and olor oscillations; the bmw beats stop at the output of 1 L f; t (1st detector detector) 1 and, respectively, Bev; H of the switch 2 polarity BO3nm (.) fi of the control terminal level (: , R inMfMiT exceeding this voltage above the threshold level specified by source 11 is stopped. - unidirectional counting down counter 14 stops the search mode and the demodulator enters the synchronous mode

A characteristic feature of this mode in the proposed device is the fixation of the phase mismatch at the inputs of the phase detector 1 at the level specified by the voltage from the output of source II, fixing of the initial frequency discrepancy between the reference and input oscillations at the level of L / 2, where l u) - the difference between the two possible values of the input signal of the demodulator of the torus

When manipulating the frequency of the input signal of a demodulator that is in synchronous operation, the difference of the total phases at the inputs of the phase detector 1 begins to change rapidly with time, which leads to a change in its output voltage in accordance with its discriminatory characteristic (for example, sinusoidal law). At the moment when this voltage passes through zero, the state of the logic output of the amplitude comparator 4 changes abruptly. Through the time interval determined by the delay unit 5, the polarity of the voltage at the output of the switch 6 polarity changes abruptly, which leads to a sharp shift in the frequency of the adjustable oscillator 8 by the value of L ijj, Ts, ej, the frequencies of the input and reference oscillations are combined. The delay of the signal of block 5 is chosen so that the oscillation frequency of the adjustable oscillator 8 coincides with the frequency of the input signal at a time corresponding to the polarity of the output of the switch 2 polarity and the reference voltage from the source code 1 1 o

After the termination of the described transients, the device is again in synchronous mode of operation, and an information frequency transfer of the demodulator signal is induced at the output 18 of the device 18.

The inertia of fights 1 and 10 was chosen. so that during the described transients

the voltages at their outputs practically did not change. This allows the device to maintain a synchronous mode of operation of the tunable generator 8 and, therefore, significantly reduce the time of transients when manipulating its frequency following the manipulation of the frequency of the input demodulator.

Claims (2)

Invention Formula 1 o A demodulator of frequency telegraphy signals containing a low-pass filter and a serially connected adjustable oscillator and a phase detector, the second input of which is the input of a demodulator of frequency telegraphy signals, characterized in that, in order to improve the noise immunity, the first polarity switches are connected in series , the block of the search and fixation of the phase mismatch and the adder, as well as the amplitude comparator, the delay unit and the second polarity switch, and the output of the phase detector is soy Dinene with the first inputs of the amplitude comparator and the first polarity switch, the second input of which is connected to the input of the delay unit and the output of the amplitude comparator, which is the output of the demodulator of the frequency telegraphy signals, the output of the polarity switchboard through a low-pass filter connected in series and the second polarity switch is connected to the second input of the adder, the output of which is connected to the input of the adjustable generator, the output of the delay unit is connected to the second input of the second polarity switch, the second input of the amplitude comparator , 2. A demodulator as claimed in claim 1, in which the phase mismatch search and fixing unit comprises a first low pass filter, the input of which is the input of the phase mismatch searching and fixing unit, amplitude comparator, reference voltage source , a generator of counting pulses, as well as a series-connected reversible counter, a digital-to-analog converter and a second low-pass filter, the output of which is the output of the block for searching and fixing the phase error, and the amplitude inputs of the comparative ra connected to outputs of the first low-pass filter and the reference voltage source respectively, the control input of the reversible counter connected to the output of the amplitude comparator and its counter input connected to vp {ode counting pulses of the generator