SU597985A1 - Arrangement for automatic phase tuning of measuring transducer intermediate frequency - Google Patents

Description

adjustable gain, the second input of which is connected to the output of the phase detector, and the output of this amplifier is connected to the input of the low-pass filter. In FIG. Figure 1 shows the structural electrical circuit of the device proposed; Fig. 2 shows the voltage dependencies of the phase difference (a is the output voltage of the main phase detector 7; b is the output voltage of the additional phase detector 8; c is the output voltage of the nonlinear element 10 g, the output voltage of the device);

The intermediate-frequency phase-locked loop device of the transducer contains mixer 1, amplifier 2 with adjustable gain, adjustable oscillator 3, low-frequency filter 4, reference generator 5, intermediate-frequency amplifier 6, main 7 and additional 8 phase detectors, EO phase shifter 9, nonlinear element ten.

The device works as follows.

The output voltage of the intermediate frequency through the amplifier b is fed to the input of the basic phase detector 7 and the additional phase detector 8, and the other inputs of the phase detectors 7 and 8 receive the voltage of the reference frequency from the reference generator 5, and the auxiliary phase detector 8 is supplied through The 90 phase shifter 9. The output voltage of the main phase detector 7 (Fig. 2a) is an error signal of the PLL system and is fed through amplifier 2 to the low-pass filter 4 to control the frequency of the tunable generator. torus 3. The output voltage of the additional phase ectopa 8 (Fig. 26) is supplied to the nonlinear element 10, which distorts the shape of the output signal, so that its effect on the regulating input of the amplifier 2 is the transmission coefficient in the region (2ts-h1) 1 where p l, 2,3,4..i, more than an order of magnitude greater than the transfer coefficient in the 2-nit region (Fig. 2c).

Thus, the dependence of the output voltage of the device on the phase difference of the intermediate frequency signal and the reference oscillator 5, which is the formed phase characteristic P (/), has a sawtooth character (Fig. 2d), with one of the slopes (negative) much steeper than the other.

Since when j, co „and oo„ with where 60pr is the intermediate frequency, ij c the frequency of the input signal, c the frequency of the tunable generator.

The working 1 cell is at different slopes of the phase characteristic and, moreover, in the real circuit there is a delay in the feedback circuit, it is possible to choose such a ratio of the slope of the slopes of the characteristics that when operating on a slope with a small slope, the system will stably be in the state synchronism. And if the working point gets into another area, parasitic oscillations will arise in the system, which will rebuild the adjusted generator 3 like a search effect, until the working point moves into an area with a small steepness, where the capture will occur.

So for a system with an integrating filter, the condition must be met to ensure stability.

Yaw)

where a is the retention band, t "is the delay time in the circuit of the circuit connection, PCP)

slope of the slope of the phase characteristic. At the same time, for a steep slope, this condition is not fulfilled, therefore, the conversion will occur according to one of the selected

algorithms 60 „p - co - 60 rjr-r or“

which guarantees the uniqueness of the transfer of phase shift at an intermediate frequency.

Claims (2)

1. Automation of radio measurements, ed. V.P. Balashov, Sov. radio, M., p. 322-323. 2. Shahgild V.V., Lovkhov A.A., Phase locked loop systems, Link, M., 1972, p. 27.