SU769758A2 - Digital demodulator of frequency-modulated signals - Google Patents

Description

one

The invention relates to radio engineering and can be used to receive discrete information.

According to the main author. St. No. 545091 is known for a digital demodulator of frequency-modulated signals, comprising a series-connected reference oscillator, a first limiter and a frequency divider and a serially connected band-pass filter, a second limiter and a differentiating chain, as well as a lower frequency filter, connected to a coupling circuit, and a trigger circuit. , a unit for determining the working frequency band and a series-connected decipher, summator, key circuit and match unit, the output of which is connected to the low-pass filter and the differential The start-up circuit is connected via a start circuit to a frequency divider, the corresponding inputs of which are connected to a decryption unit and a frequency band detection unit, the output is connected to the control input of the key circuit, while the second output of the start circuit is connected to the corresponding inputs of the decoder and the operating bandwidth block 1 .

However, such a demodulator has low noise immunity.

The purpose of the invention is to increase accuracy.

For this purpose, in a digital demodulator of frequency-modulated signals, comprising a series-connected reference oscillator, a first op-taler and a frequency divider and a series-connected band-pass filter, a second limiter, and a differentiating chain,

10 as well as a low-pass filter connected to the decision circuit, and a start circuit, a block for determining the working frequency band and a successively connected decoder, adder, key circuit and

15, a comparison unit, the output of which is connected to a low-pass filter, and a differentiating chain, through a startup circuit, is connected to a frequency divider, the corresponding outputs of which are connected to a decoder and a frequency band determination unit, the output of which is connected to the control unit; the output of the start circuit soya diHeiH with the corresponding inputs of the decoder and the unit for determining the working frequency band; the control unit and the operational memory unit are entered, the output of the differentiating chain and the output of the first limiter through the control unit

30 is connected to the first input of the clock frequency divider, between the second input and the ADDITIONAL output of which the memory unit is turned on, the output of which is connected to the corresponding input of the control unit.

The drawing shows a structural electrical circuit of the demodulator.

The demodulator contains a reference generator 1, limiters 2, 3, a divider 4 frequencies, a band-pass filter 5, a differentiating chain 6, a low-pass filter 7, a decision circuit 8, a start circuit 9, a block 10 for determining the working frequency band, a decoder 11, an adder 12, key circuit 13, comparison unit 14, block 15 un, pa; events and operative memory block 16.

Works demodulator the following way.

The signals arriving at the input of the demodulator are filtered in bandpass filter 5 and are limited in limiter 3. The rectangular sequence of frequency-manipulated pulses from limiter 3 goes to differentiating chain 6. From the output of differentiating signal 6, short pulses corresponding to zero signal transitions, arrive at the start-up circuit 9 and block 15. The start-up circuit 9 generates pulses for the beginning of the division of the frequency of the reference oscillations of the divider 4 and the interrogation pulses from the signals with differentiating chain 6 And fratora and the block 10, the following periods with the frequency acting on the input signal. The frequency division start pulses immediately follow the polling pulse, and a divider 4 is set to the initial state, and the memory of block 16 is reset. The pulses coming from the differentiating chain 6 to block 15 coincide in time with the pulses of the beginning of the frequency division of the reference oscillations. The block 15, according to sipnals from the differentiating chain 6 and the block 16 times, allows the reference oscillations to pass from the reference generator 1 through the limiter 2 and the main input of the divider 4, if the block 16 has not recorded the transition signal of the divider 4 beyond the set threshold, and prohibits the flow of the reference fluctuations on the divider 4, if there was a record of the transition state of the divider 4 state over the set threshold in block 16.

After the impulse-beginning of the division, divider 4 begins to divide the frequency of the reference oscillations. The division process continues until the momentum of the millet is received, i.e. a period of time equal to the period of the frequency of the input signal.

If "at the input of the demodulator, a signal acts with a frequency that is in the working frequency band, then for the input signal, the divider is 4 P1p m the corresponding state. According to the polling pulse, block 10 generates a signal that opens the key circuit 13 and, therefore, the signal from the output of the decoder 11 through the adder 12 enters the processing in block 14, filter 7 and the decisive circuit 8. As a result of processing, the information parcel 1 or “O according to the frequency of the input signal.

If "at the input of the demodulator, a signal with a frequency higher than the highest frequency of the operating band is in effect, then the division time of the reference oscillations will be less than the previous one, and the state of divider 4 will not reach the allowed one, unit 10 will produce a signal that closes the key circuit 13. Thus The input signal will not be output in this case.

If at the input of the demodulator a signal acts with a frequency that is a multiple of times the operating frequencies, the division of the reference oscillations will take a longer time, the state of divider 4 will go beyond the threshold, which B will write the corresponding signal. In this case, the block 15 receives a signal prohibiting the supply of reference oscillations to the divider 4.

Divider 4 will maintain its state until the moment when the polling pulse has been generated. The block generator 10 and block 10 defines this state as forbidden and, therefore, demodulation of such a signal will not be produced.

In the proposed demodulator, in contrast to the known devices, the multiplicity errors are excluded.

As a result of their elimination, the accuracy of receiving discrete information in CONFERENCE is increased. The effects of powerful concentrated noise existing in overloaded wire and radio communication lines.

Claims (1)

1. USSR author's certificate No. 545091,. H 04L 27/10, 1974 (prototype).