SU586398A1 - Four-pole network group time lag meter - Google Patents

Description

10-1, the invention relates to radio measuring devices, in particular, to measuring group delay times of two-port networks. Measurement of the group time of four-pole delays with the sickness and the li of the high-frequency region is an urgent task of the radio meter. Limes are a measurer of the identity of the phase characteristics of quadrupoles in the field of primary materials, the contents of a sawtooth generator, a controlled oscillator, a frequency generator, a mixer, a quadripole under study, an amplitude detector, a phase detector and an indicator. In such a meter, the lack of frequency stability in the passband of the quadrupole under study leads to a decrease in resolution and makes it difficult to work with voltages whose frequencies change during the measurement process. In addition, the indicator operates in the frequency band, which leads to large dynamic errors. The purpose of the present invention is to eliminate frequency instability during operation of controlled oscillators in the frequency band while maintaining a constant difference between them and increasing measurement accuracy in the high frequency range, which is achieved by introducing into the phasor equalizer, its mouth (), onopHOJO generator n of the second control of the jiHCMoio gene) ator. The scheme of the proposed meter shown pa drawing. It contains a sawtooth voltage generator 1, controlled oscillators 2 and 3, mix 4, traced quadrupole 5, phase grapher 6, amplitude detector 7, reference generator 8, phase detector 9 and indicator 10. Voltage U (t) from generator output 1 is fed to the inputs of controlled oscillators 2 and 3, whose frequencies are modulated according to a linear law, as well as to one of the inputs of the indicator 10, in order to obtain a linear sweep on the screen of a CRT tube. Voltage Li Z7isin (Oi-fAoui (71 (01 from the generator 2 output and voltage Uz 62sin (B2 + Aci) 2 (0 HGO from the generator 3 output is fed to the inputs of the quadrupole 5 under study and the mixer 4. The difference between frequencies Ui and Uz, taken from controlled generators 2 and 3, remains constant at any time and is equal to Q uJi (02, since Ds (0 Aco2 (0 and therefore the output voltage of the two-port network being investigated is: output (): K + (); T () + iW +. + A «a ();

3: () + m. (D).

When Ati) i (t) (i) 2 (t) & (i) (t), THAT is provided by the phase-matching device 6, finding the nonlinearity of the phase characteristic in the passband of the quadripole under study reduces to measuring the phase difference Aff (t) (fi ( t) -fzGO between two low-frequency signals constant in frequency, and the group delay time of the studied quadrupole is equal to

. (0.

The frequency Q can be made sufficiently small compared with the frequencies i i and ω2.

From the output of the investigated quadrupole 5, the voltage (output is fed to the amplitude detector 7 to isolate the low-frequency envelope of the beating of the voltages Ui and Uz. With linear detection, the voltage on the load of the amplitude detector

t / Q (t) K Ul + Ul + 2Lf, Lf, sm (Qf + y - b)

This voltage is applied to one input of the phase detector 9, to the other input of which voltage is supplied from the output of the reference oscillator 8. The low frequency voltage taken from the phase detector 9 carries information about the nonlinearity of the phase characteristic of the quadrupole 5 under study at this frequency, t. e. at the given time. If an electron-beam tube is used as an indicator 10, then on the tube screen the beam will draw a dependence of Tz on the frequency m.

To maintain the frequency Q in the measurement process, the meter uses phase-matching device 6, to one input of which voltage is applied from the output of the mixer 4, and to the other input - voltage from the second output of the generator 8 of the reference voltage. From the output of the phase-matching device 6, this voltage is applied to one of the inputs of the controlled oscillator 2, which ensures the constant difference between the frequencies of the controlled oscillators.

Thus, the meter eliminates the frequency-phase errors of the indicator device while reducing the dynamic errors, which allows to increase the measurement accuracy.

In addition, the graduation of indicator 10 remains constant, since th const. As a result, the meter can operate in a wider frequency range and automatic mode.

Subject invention

The quadrupole delay group time meter, containing a sawtooth generator, connected to one of two generators, which are connected to the mixer inputs, an amplitude detector connected to a phase detector, the output of which is connected to an indicator, three terminals for connecting the four-pole network, one of which are connected to the input of an amplitude detector, and the other two are connected to the outputs of generators, characterized in that, in order to improve the measurement accuracy, to expand the frequency range and automation, it is equipped with a phase-equalizing device and a reference generator, while the sawtooth generator is connected to the input of the second generator, the mixer output is connected to one of the phase-equalizing device inputs, the other input of which is connected to the reference voltage generator, the phase-equalizing device output is connected to one from the generators, and the outputs of the amplitude detector and the reference voltage generator are connected to the input of the phase detector, the output of which is connected to the indicator.