SU1059694A1 - Device for demodulation of phase-shift keyed signals - Google Patents

Abstract

DEVICE for demodulating FSK signals, comprising a counter and a serially coupled bandpass filter, a pulse shaper and a shift register, a second input and vUhod which soodiyeny respectively yield of the reference oscillator and to the first input of the adder, characterized in that, in order to increase noise immunity, into it, a decoder and a regenerator are entered, the inputs of which are connected to the outputs of the shift register and the adder, the second input of which is connected to the output of the pulse former and to the first the second input of the counter, to the second input of which the Output of the reference frequency generator is connected, and the outputs of the counter are connected to the inputs of the decoder, the output of which is connected to the third input of the adder. (Ls

Description

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The invention relates to telecommunication technology and can be used in voice telegraph equipment. A known detector of frequency-manipulated (FM) signals, containing successively connected pulse formers and a counting trigger, as well as two calibrators and a logic unit, while the inputs of the first and second calibrators are connected, respectively, with the forward and inverse inputs of the counting trigger and the corresponding inputs of the logic block ij. However, in this detector prevails in the received information, which, in turn, causes the occurrence of errors in synchronization. This leads to an increase in the probability of errors in the receiving information. The closest to the present invention is a device for demodulating frequency-manipulated signals with a counter and serially connected bandpass filter, a pulse shaper and a shift register, a second input and an output which are connected respectively to the output of the reference frequency generator and to the first input of the adder 2. However, the known The device has a low noise immunity. The purpose of the invention is to improve noise immunity; This goal is achieved in that a device for demodulating frequency-manipulated signals comprising a counter and a successor .fio are connected by a band-pass filter, a pulse driver and. the shift register, the second input and output of which are connected respectively to the field., the generator of the reference frequency and the first input of the adder, entered the decoder and the regenerator, the inputs of which are connected to the outputs of the register of the shift and adder. the second input of which is connected to the output form of the pulse body and to the first input of the counter, to the second input of which the output of the reference frequency generator is connected, and the outputs of the counter are connected to the inputs of the decoder, the output of which is connected to the third input. adder. FIG. Figure 1 shows the structural electrical circuit of the device proposed; FIG. 2 is a plot of stresses that exemplify his work. A device for demodulating frequency-manipulated signals contains a band-pass filter 1, a driver of 2 pulses, a generator 3 of the reference frequency, a shift register 4. counter 5, the decoder 6, the adder 7 and the regenerator 8. The device operates as follows. - The frequency-manipulated signal corresponding to the transmitted information (Fig. 2a, e) and received from the communication canapa is limited by spectrum to filter 1 filter 1 (Fig. 26, g) and is fed to the input of the imaging unit 2 pulses., Producing short pulses moments of the transition frequency-manipulated (FM) signal through the zero level (figv, h). The pulse from the output of the driver 2 pulses is fed to the first input of the shift register 4 and is advanced by the clock pulses of the reference frequency generator 3 received at the second input of the shift register 4. The number of cascades of the shift register 4 is chosen equal to KQ (this ensures a delay of pulses by time, 5 T - 0.5 Tg, where TH and Tg are periods of the lower and upper frequency characteristics, respectively, where K is determined by the number of reference frequency pulses. Simultaneously with Key 4 of the shift impulse from the output of the imaging unit 2 impulses arrives at the second input on the day of 1mator 7, increasing the state of the latter by 1. Each impulse that passed the register 4 of the shift arrives at the second input of the regenerator 8. Regenerator 8 at the moment of arrival of the impulse analysis The state of adder 7 (- impulse l and Fig. 2i - impulse 2). If the state of adder 7 is equal to one, which corresponds to the reception of the period of the FM signal, the duration of which is greater than T, then the regenerator 8 makes a decision to receive information of positive polarity (Fig. 2d, k). If the state of adder 7 is greater than one (fig, 2d is pulse 3 and fig, 2i is pulse 4), which corresponds to the reception of a period whose duration is less than T, then the regenerator 8 decides on receiving negative information polarity (fig, 2d, k), after analysis by the regenerator 7 adder state pulse passing the shift register 4 ,, decreases state cyisiMaTOpa 7 per unit. At the initial, instant, the state of the adder 7 can be arbitrary, not corresponding to the number of pulses currently in the shift register. In this case, the nd linearity of the received information by the regenerator 8 is not determined correctly. To eliminate the possibility of improper razots, counter 5 and

decoder 6. Counter 5 measures the duration of the FM-si-nala period, expressed by the number of clock cycles of generator 3. For this, the pulses from the output of the driver 2 pulses arrive at the second input of counter 5 and set it to the zero state, and the incoming at the first input of counter 5 clock pulses of oscillator 3 increase its state. When the duration of the FM signal period is greater than Td, the state of counter 5 exceeds the number of K o and there are no pulses in shift register 4. The decoder 6, which is tuned to the number KO, selects this state of the counter 5 and generates a pulse, which sets the adder 7 to the zero state on the 3rd input. In the distance. Our counter 5 and the decoder do not affect the operation of the device.

Thus, the use of the proposed device for demodulating FM signals in comparison with the known one allows reducing the synchronization error of the parcels due to the redistribution (alignment) of the edge distortions that arise when the edges of the received information are restored, which, in turn, increases the noise immunity of the received information.

In particular, tests at a speed of 1200 bps showed that the KO I-IO error rate of the proposed device was obtained when the difference between signal levels and noise was 5 dB.

5 less than the known device.

Thus, using the invention in a voice wiring apparatus can significantly improve the noise immunity of received information.

Claims (1)

DEVICE FOR DEMODULATION OF FREQUENCY-MANIPULATED SIGNALS, comprising a counter and a series-connected bandpass filter, a pulse shaper and a shift register, the second input and input of which are connected respectively to the output of the reference frequency generator and to the first input of the adder, which differs in that, in order to increase the noise immunity , into it, a decoder and a regenerator are introduced, the inputs of which are connected to the outputs of the shift register and the adder, the second input of which is connected to the output of the pulse shaper and to the first input ohm meter to the second input of which is connected to the output of the reference oscillator, and the counter outputs are connected to inputs of the decoder which output is connected to the third input of the adder. i to © Fig. 7 SL C 1SP> ί