SU489088A1 - Group lag time meter - Google Patents

Description

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The invention relates to a rational and measuring technique and can be used in the development of gauge group time meters (ayavyvany (GVZ) of two-port networks from paths with geographically separated VHOCOM and OWLER.

There is a known group lag time meter, which contains a test signal generator, a measuring frequency generator, the output of which is connected to one of the amplitude modulator inputs and one of the receiver inputs, the other input of which is connected to the four pole pole.

Due to the fact that the parameters of the modulator elements of a known meter group are complex and depend on the level of the modulating voltage, along with amplitude modulation, there is an additional parasitic phase modulation. . When passing an amplitude-modulated signal with spurious phase modulation, through a quadrupole, the amplitude-frequency characteristic (AFC) of which

non-uniform, i.e. the steepness of the frequency response is not equal to O, there is a transformation of the parasitic phase modulation into an additional amplitude modulation with a frequency equal to the measuring frequency L. 1) aza pgi-. The extra amplitude pitch is arbitrary and depends only on the properties of the measured quadrupole. As a result, there are significant errors in the measurement of the GZZ of three-pole with uneven frequency response.

The purpose of the invention is to improve the measurement accuracy by reducing the level of parasitic phase modulation.

This is because the group time meter contains an amplitude limiter, a phase detector and a phase shifter, the output of which is connected to another input of the amplitude modulator, the output of which through the amplitude limiter is connected to one of the inputs of the detector, the other input of which is input phase shifter connected to the test generator output

. signal, and the output of the phase detector is coupled to the control input of the phase shifter.

The drawing shows a functional diagram of the meter. The proposed meter contains a test signal generator 1, the output of which is connected to the input of the amplitude modulator 2. Another input of the amplitude modulator is connected to the generator 3 of the measuring frequency. The output of the amplitude modulator is branched into two channels - measuring and reference. A measuring quadrupole 4 is included in the measuring channel. The measuring and reference channels are connected to the inputs of receiver 5. The output of the amplitude modulator 2 is also connected via amplitude limiter 6 to one input of the phase detector 7, the other input of which is connected to the output of the test signal generator 1 and the output A phase detector 7 is connected to a control input of a phase shifter 8 connected between a test signal generator i and an amplitude modulator 2.

The meter group is as follows

in a way. The high-frequency signal of the generator J. of the test signal through the phase shifter 8 is fed to an amplitude modulator 2, where it is modulated by the voltage of the generator 3 of the measuring frequency. fJbicoKoiacTOTHbie amplitude-modulated Hbie c p lgely from the measuring and reference channels arrive at the inputs of receiver 5, in which the phase difference between the envelopes of the measuring and reference channels is detected and measured. Difference; The phases of the envelopes are a measure of the GDT of the measured quadrupole 4. In this case, the rise of the parasitic phase modulation resulting from a change in the complex parameters of the modulator 2 could lead to significant errors in the measurement of the GDT of the quadriple with uneven frequency response. To reduce the effect of parasitic phase modulation, stenals with

the output of the amplitude module 1-ora 2 enters the amplitude limiter b, in which the amplitude limit occurs, i.e. the signal input to the phase detector 7 is a signal with a frequency equal to the generator frequency I of the test signal and additional parasitic phase modulation. It can be written as

and l i m {Wot- -u {psmnt)

where I is the amplitude of the limited signal; D (- deviation of phase modulation,

arising in the amplitude modulator 2:

L - measuring frequency; Wg - test frequency.

The other input of the phase detector 7 as a reference signal receives a signal from the generator 1 of the test signal. It is written as

Output voltage of the phase detector 7

will be proportional to the phase difference of these signals and can be written as

where Cf - ko1 / 3 Kfd-L 9 Sin-fit

transmission efficiency of the phase detector 7.

The amplitude limiter 6 operates in a very small dynamic range and does not introduce phase distortion. The output signal of the phase detector 7 as a control signal is fed to the control input of the phase shifter 8 connected between the test signal generator 1 and the amplitude modulator 2. The control voltage of the phase detector 7 will affect the phase shifter 8 so that the voltage phase difference At the inputs of the phase detector, the detector was constant and dependent on the specific phase detector circuit and thereby connects the phases of the voltage of the test signal generator and its output (amplitude modulated voltage Stator, t. (. The magnitude of the phase modulation deviation at the output of the DC modulator will be O. The accuracy of maintaining the phase difference depends on the sensitivity of the phase shifter 8, the control voltage gain V, j and is limited

about

system stability. Accuracy of maintaining a constant phase difference can be achieved in the order of hundredths of a degree, and the magnitude of the phase deviation becomes negligibly small, not affecting the accuracy of the GDT measurement. This reduces the measurement error of the GDZ four-port system with uneven frequency response, which is almost all radio engineering circuits.

Subject invention

The group time meter is a generator containing a test signal generator, a measuring frequency generator, the output of which is connected to one of the amplitude modulator inputs, the output of which is connected to the quadrupole input and one of the receiver inputs, the other input of which is connected to the quadripole output, different in order to increase the measurement accuracy by decreasing the level of parasitic phase modulation, it contains an amplitude limiter, a phase detector and a phase shifter, the output of which n drugn1 with input amplitude modulator the output of which through the amplitude limiter is coupled to one input of the phase detector, another input of which the input and the phase shifter connected to the output of the test signal generator and the output of the phase detector is coupled to a control input of phase shifter.

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