SU411386A1 - - Google Patents

Description

PHASOMETER WITH FREQUENCY CONVERSION DEVICE

one

This invention relates to radio measurements and radio receivers.

Devices are known in which frequency conversion of input signals is used to transfer the phase shift between two input signals to a fixed intermediate frequency and switching (switching) of input signals is used. However, to achieve a positive effect, elimination of phase-frequency errors requires the use of switches capable of operating at high frequencies with a small high-frequency signal passing through a closed (open) key, in addition, the keys must have identical frequency-frequency characteristics in a wide frequency range of input signals.

The creation of such switches is very difficult in the range of 1-150 MHz, and the imperfection of the switch significantly reduces the measurement accuracy.

The aim of the invention is to eliminate frequency-phase and amplitude-phase errors. This is achieved by the fact that in the proposed device two auxiliary modulating oscillators are connected to the modulator of the frequency converter via a key, the low-pass filters of the converter device through limiting amplifiers and

the two-channel switch is connected to the phase indicator, and the output of the generator of switching pulses is connected to the control winding of the mentioned switches.

FIG. 1 shows a block diagram of the device; in fig. 2 - signal spectra.

The device contains mixers 1, 2, 3, adjustable local oscillator 4, control element 5, phase detector 6, reference generator of phase-automatic frequency control PLL 7, amplitude modulator 8, auxiliary modulating low frequency generator 9, low-pass filters 10 and I ,

a key 12, a second auxiliary modulating generator 13, a generator of switching pulses 14, amplifiers-limiters 15, 16, a key P, a phase indicator 18.

In the first half-cycle of switching, the switch 12 is in the position P yus (cur-f-mode), the mixers 1 and 2 are given the signals {Us, (coq + pF and f / cj ((Ac + p2) and the voltage of the local oscillator 4, amplitude modulated voltage

the frequency of the mode of the auxiliary modulating generator 9 (see Fig. 2, a). At the output of the mixers, after filtering the product of the conversion of frequencies bs and (south + mode.), We obtain the voltages Ui and f / 2, the frequency and phase of which

respectively equal.

(c - (ir + mod1) + i + +,

 2 + T, +, 4-. ,

c - (+ “mod,) + a + Aspc, +,

  + +. ,

where Yus is the frequency of the input signal; coh is the frequency of the heterodyne signal; (sos-sog) o) op. - frequency of the reference generator

PLL systems;

(Omod.- frequency modulating oscillator;

ff f2 - phase I and II channels; Dfs ,, Aspc2-amplitude-phase shifts of mixers 1 and 2, respectively;

A (ru "Dfu ,, - amplitude-phase shifts arising in amplifier x - limiters 15 and 16, respectively: 2 - frequency tuning filters

low frequencies 10 and 11.

The phase difference between the voltages Ui and t / 2, measured by phase indicator 18 in the first half-cycle of switching, is equal to

  (Pi +, +,) - (“P2 +. + (1)

In the second half-cycle of switching, the key 12 is in the position Pg, ace (coz + d) mod. D) (see Fig. 2.6), the voltage at the output of amplifiers 15 and 16 is equal to Ul and Uz, the frequency and phase of which are respectively from expressions

K + “Vmod,) Y) ,. - (pi + afs, +,

 d + d (pc, + asra,

("R +,) - BC - a + f with. h-, Q + D (pc, +. - 9g.

where Shmod.gr and Smodg + 2Q is the frequency of the second auxiliary modulating oscillator 13, 2Q more than the frequency mod.,

The phase difference between the voltage Ul and f / s, measured by the phase indicator in the second half-cycle of switching, is equal to

Wed: (D (pc. + Afy, - f i) - (, - ATU, - p.) (2)

Key 12 is periodically controlled by pulses from generator 14. The same generator controls key 17, which performs cross-switching of f / 2 and U signals at the phase indicator 18 input. In case of cross-switching with key 17, the resulting reading of the phase meter indicator is equal to the difference between the two readings of f1 and fps considering expressions (1) and (2) we get

Tizi (1 - P) - (1 - Ta).

where (f1-fg) is the measured phase difference between the voltages at the input of the phase meter.

In the proposed phase meter, switching is performed at a fixed low intermediate frequency at the phase indicator input, and the second switch operates at low constant frequencies of the modulating oscillators. Consequently, keys are subject to much less stringent requirements than in known devices.

Subject invention

A phase meter with a frequency converter and an automatic phase auto-adjusting device, characterized in that, in order to eliminate frequency-phase and amplitude-phase errors, two auxiliary modulating oscillators are connected to the modulator of the frequency converter via a key, the filters of the mixer of the converter device through amplifiers-limiters and the two-channel switch is connected to the phase indicator, and the output of the generator of switching pulses is connected to the control winding of the mentioned switches.

,) c - (((Won ° 3,) t,

L -. j (Mo8z and U.

with

CJf. s

one

 ShmsZ -

± zz: