SU396811A1 - FREQUENCY DISCRIMINATOR - Google Patents

Description

one

The present invention relates to frequency discriminators based on the lrinzine conversion of the frequency modulation of the input signal to the phase signal, followed by phase detection.

A frequency discriminator is known that contains a frequency modulation to phase converter, made in the form of a quartz filter, connected in parallel with an input line to the delay line and a phase detector, whose inputs are connected to the outputs of the quartz filter and the delay line.

The disadvantages of the known device include the inability to control the sensitivity and noise immunity of the discriminator at a constant operating frequency.

In order to eliminate this residual, the proposed multi-discriminator between the delay line and the phase detector includes a band-pass quartz filter covered by a negative feedback circuit consisting of a series-connected phase rotator and amplifier with adjustable gain factors.

The drawing shows the proposed frequency dnskra.minator. It contains a quartz filter /, a phase detector 2, a delay line 3, a band pass quartz filter 4, a phase shifter 5 and an amplifier 6 with an adjustable power factor}.

The device works as follows.

The input frequency-modulated signal enters a quartz filter / with a reference phase characteristic and input to the delay line 5. At the output of the quartz filter 1, the signal is shifted in phase and related to INITIAL} by an amount equal to the horizontal deviation of the frequency-modulated signal from its carrier. The signal from the output of the quartz filter / is fed to the phase detector 2. The delay line 3 serves to: create at the nominal frequency a quartz filter / phase shift equal to- (2n + 1)

t

where, 1, 2, ....

From the output of the delay line 3, the signal is fed to the input of the band-pass quartz filter 4. The nolos of the quartz filter 4 should be slightly wider than the band of filter 1.

In this case, it will not affect the size of the working band of the discriminator. Filter class 4 but attenuation (phase) should be lower compared to filter 1.

Phaser 5, together with broadband amplifier 6, provides a phase shift of the signal in the feedback circuit of the band-pass filter 4 equal to 180 °.

Do not change the gain of the amplifier 6 in the quartz feedback circuit

Filter 4 varies the slope of its phase response and frequency band, therefore, the sensitivity of the discriminator and its noise immunity change.

Since the detector characteristic of the discriminator is a function of i | i (a - p), where a is the phase characteristic of the quartz filter and p is the phase characteristic of the band pass crystal 4, its temperature and time stabilization is possible. To realize this possibility, it is necessary that the temperature coefficient of frequency and the aging of all the quartz resonators of the filters / and 4 are the same. This requirement can be approached by fulfilling all quartz resonators on a monoblock of quartz of the selected slice.

Subject invention

A frequency discriminator, containing a quartz filter connected in parallel at the input and whether there are delays, the outputs of which are connected to the inputs of the phase detector, characterized in that a band pass is switched on between the delay line and the phase detector to control the sensitivity and noise immunity of the discriminator. a quartz filter covered by a negative feedback circuit consisting of a series connected phase shifter and an amplifier with an adjustable gain factor.