SU1109867A1 - Frequency discriminator - Google Patents

Abstract

FREQUENCY DISCRIMINATOR auth. No. 980247, about so and so that, in order to increase noise immunity, the inputs of the frequency shift detection unit are connected respectively to the outputs of the threshold unit and the reference pulse generator through input 1, when this between the inverter output and the other input of the OR element is connected in series with the additional L-trigger, the third element AND and the pulse expander, and the B-input of the additional D-flip-flop is connected to the output of the reference pulse generator and another input of the third element I.

Description

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0t / t. / I 1 The invention relates to radio engineering and can be used in various automated radio devices. According to the main auth. No. 980247, a frequency discriminator is known comprising a series-connected gyromagnetic filter, an amplitude detector, a threshold unit, as well as a reference pulse generator connected via a fast tuning unit to the first tuning input of the gyromagnetic filter, a slow tuning unit connected to the second tuning input of the gyromagnetic filter, determining unit frequency shift, the inputs of which are connected respectively to the outputs of the threshold unit and the reference pulse generator, the frequency determination unit the wig is made in the form of a b-trigger, the outputs of which are connected to the inputs of the differential amplifier and the first inputs of two elements And, the second inputs of which are connected to the output of the counting pulse generator, the outputs of elements And are connected to the inputs of the reversible counter, and the output of the differential amplifier is connected to the input of the lower filter CO frequencies. However, the disadvantage of the known frequency discriminator, limiting its scope of use, is that correct frequency discrimination occurs only when one frequency is present in the capture band. When there are several frequencies in the capture band, for example, measures, a signal, spurious combinational frequencies or other interference, the discriminator does not work correctly and the signal at its output is no longer proportional to the frequency offset of the input useful signal, but proportional to the half sum of frequency offsets of the useful signal and the highest spurious frequency. The purpose of the invention is to improve noise immunity. The goal is achieved by the fact that in the frequency discriminator, which contains, respectively, a gyromagnetic filter, an amplitude detector, a threshold unit, and a reference pulse generator, connected through a fast tuning loop to the first tuning input of the gyromagnetic filter, is a slow tuning unit. 72 connected to the second tuning input of the gyromagnetic filter, a frequency shift detection unit, the inputs of which are connected respectively to the outputs of the threshold unit and the reference pulse generator, the frequency shift detection unit is made in the form of a T-trigger, the outputs of which are connected to the inputs of the differential amplifier and the first inputs of two elements And, the second inputs of which are connected to the output of the generator of counting pulses, the outputs of the elements And are connected to the inputs of the reversible counter, and the output of the differential amplifier with Connected to the input of the low-pass filter, the inputs of the frequency shift detection unit are connected respectively to the outputs of the threshold unit and the reference pulse generator through the input of the inverter and the element. OR, the inverter output and another input of the element OR are connected in series with an additional 1) trigger, the third the element And the pulse expander, and) the input of the additional b-trigger is connected to the output of the reference pulse generator and another input of the third element I. Figure 1 shows the structural electr Ceska diskriminatoraJ frequency diagram of the Figure 2 timing diagrams for explaining its operation. The frequency drive 5minator contains a gyromagnetic filter 1, a slow tuning block 2, a 3-beat tuning block 3, a reference pulse generator 4, an amplitude detector 5, a threshold block 6, an inverter 7, a frequency shift detecting block, execute the B-trigger 8 and an additional D trigger. 9, element OR 10, reversible counter 11, expander 12 pulses, differential amplifier 13, low-pass filter 14, oscillator 15 counting pulses, first, second and third elements AND 16-18. The frequency discriminator works as follows. The generator 4 - reference pulses generates a signal in the form of a meander (Fig.2a) and synchronizes the block 3 quick adjustment. The quick adjustment unit 3 with triangular bipolar pulses of current provides a linearly-sweeping gyromagnetic filter 1 (FIG. 26). The sweeping occurs on both sides of the center frequency fo of the frequency discriminator, the double sweep amplitude is equal to the capture band of the frequency discriminator. The intervals of the input frequency in the passband of the gyromagnetic filter 1 are selected by the amplitude detector 5 (Fig. 2c). Figure 2 shows the case when the input frequency f is useful; itfj and the frequency of interference. The signal from the amplitude detector arrives at the threshold unit 6, forming rectangular pulses whose leading edge captures the moments of frequency falling into the passband of the gyromagnetic filter 1 (let's call them pulses frequency detection), is fed to the input of the inverter 7. The pulse from the output of the inverter 7 is fed to the C inputs of D-flip-flops 8 and 9. Inverter 7 is used to form a flip of D-triggers on the falling edge of a frequency detection pulse, and m, dispose of the effect of this pulse width for clarity rabotychastotnogo discriminator. The pulses from the output of the inverter 7 (Fig. 2d), by their positive differences corresponding to the falling edges of the frequency detection pulses, set the additional i-trigger 9 to one in the fast sweep-up cycle (i.e., then, when on the D input of the D-trigger 9 the reference pulse is present) and the D-trigger 9 is set to zero in the down sweep step (Fig. 2e). The pulse from the output of the T-trigger 9 is fed to one input of the element And 18, to the other input of which receives a reference pulse from the generator 4. At the output of the element And 18 a pulse is formed (Fig. 2e), from the end of the action of the detection pulse

useful frequency. in a sweep stroke up to the end of this beat. The pulse from the output of the element And 18 is fed to the input of the expander 12 pulses, which forms the output pulse two times wider than the input, this output pulse goes to one input of the SHSh 10 element, to the other input of which the reference pulse comes from the output of the generator 4. Pulse to output the element OR to (fig.2zh) enters

-INVERSE L-trigger 8, pa: fsshap cfd transfer to unit filled with a pulse of detection of a useful frequency and protecting it from spurious

overshoot to zero by impulses of external interference. In the sweep cycle downstream of the pulse from the output of the element OR IO, the D-flip-flop 8 is set to zero by the trailing edge of the detection of the useful frequency. The pulses at the direct output of the trigger 8, the duration of which is proportional to the frequency shift of the useful frequency relative to the upper one.

the boundaries of the capture band are shown

on figs. The duration of the pulses at the inverse output of the T5 flip-flop 8 is proportional to the frequency offset of the useful frequency relative to the lower boundary of the capture band. The pulses from the outputs of the D-trigger 8 are fed to the inputs of the differential amplifier 13, the output of which produces a two-sided signal (Fig. 2i). Average value

This bipolar signal, proportional to the difference in pulse durations from the outputs of the TI trigger 8, is highlighted after filtering this signal by the low-pass filter 14. it

the average value is proportional to the shift of the useful frequency relative to the center frequency, and there is the analog output signal of the frequency discriminator (Fig. 2k). Digital output

frequency discriminator signal

formed similarly. The pulses from the output of the t-trigger 8 are filled with counting pulses using a generator of 15 counting pulses and two elements AND

16 and 1.7 and are fed to the inputs of the reversible counter 11. The output binary number is proportional to the difference of the durations of the output pulses of the L-trigger 8, i.e. in proportion

the frequency shift of the input signal relative to the center frequency, and is the output digital signal of the frequency discriminator.

The technical and economic effect of the proposed frequency discriminator is that it allows for automatic tuning of the frequency of the generators, subject to the existence of lateral interference in the capture band, while the known is not operational under these conditions.

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Claims (1)

FREQUENCY DISCRIMINATOR P 980247, characterized in that, in order to increase the noise immunity, the inputs of the frequency shift detection unit are connected respectively to the outputs of the threshold block and the reference pulse generator through the inputted inverter and OR element, while between the inverter output and the other input of the OR element are included in series-connected additional I) -trigger, third element And and a pulse expander, and the D-input of the additional D-trigger connected to the output of the reference pulse generator and another input of the third element I. 1109867 1