SU970260A1 - Device for measuring phase delay of four-terminal network - Google Patents

Description

The invention relates to electrical measurements, in particular to measurements of parameters of quadrupoles, and can be used to measure the absolute value of the phase delay of an ultrasonic delay line for color television, where delay lines with a nominal value of 63943 + 2 are not used.

It is known a device that implements a method in which oscillations with a varying frequency and the number of phase-frequency control points are counted at the input of the tested quadrupole and at the reference channel. quadrupole characteristics 1.

The disadvantages of this device are the difficulty of implementing a stable oscillator tunable over a wide range, a speed of 1 frequency meter for fixing the frequencies of control points and an arithmetic logic device, and the measurement performance is low, because when the generator is tuned it takes time to set the generator modes at the new frequency.

It is also known a device for measuring an absolutelyEo value of a phase delay, comprising a generator

sinusoidal oscillations connected to the driver of the counting pulses ai with the first input of the switch. The switch output is connected to the first input of the phase delay meter within one period and to the input of the test quadrupole connected to the second input of the phase delay meter within

10 single periods to the second input of the period number meter. The counting input of this meter is connected to the output of the counting pulse generator and. pulse generator input. The device also contains an adder connected to the outputs of the phase delay meter within one period and a meter for the number of periods, and a control unit connected to the control inputs of the switch, a number-period meter and a phase delay meter within one period. In this case, the output of the pulse generator is connected to the first input of the meter

25 numbers of periods and with the second input of the commutator 2 J The disadvantage of the device is the low accuracy in measuring the number

30 periods, since the measurement of the number of periods is made on a pulsed signal, the delay of which is determined by the group propagation velocity, which differs from the phase velocity. The purpose of the invention is to improve the measurement accuracy. This goal is achieved by the fact that a device for measuring the phase delay of a quadrupole containing the input and output terminals for connecting the test quadrupole connected in series (generator, driver and pulse generator, switch, phase meter, period number meter, totalizer and control unit, outputs which are connected to the corresponding star of the switch, phase meter and gauge of the number of periods, the output of which is connected to the adder, the input and output terminals are connected to the phase meter, output The generator is connected to the input of the adder, the generator output is connected to the input terminal through a switch, and the output of the imager and output terminal are connected to the corresponding inputs of the number of periods, an adjustable delay unit is connected to the input of the switch, and inputs to the outputs of the pulse generator phase meter, line delay, the output of which is connected to the corresponding, the input of the meter for the adsl periods, and the input with the output of the heater of pulses. In FIG. 1 shows the block diagram of the proposed device; FIG. 2 is a timing diagram explaining the operation of the proposed device. A device for measuring the phase delay of a quadrupole contains a generator of 1 sinusoidal oscillations connected to a shaper of 2 counting pulses and to a first input 3 of a switch 4. A generator of sinusoidal oscillations is a generator with a quartz resonator. The shaper of countable pulses is an amplifier-limiter. The output of the switch 4 is connected to the input of the tested quadrupole 5 and to the first input b of the phase meter 7, which is a stroboscopic phase meter calibrated in units of time. A second input 8 of the phase meter 7 and a second input are connected to the output of the test quadrupole 5, p 9 meter 10, the number of periods, the counting input 11 of which is connected to the output of the generator 2 counting pulses and the input of the generator 12 pulses. The 10 period number meter contains a coincidence circuit (start-stop) and a pulse counter. Pulse generator 12 contains a synchronization circuit (counting pulse divider) and an output driver. The output of the pulse generator 12 is connected via the delay line 13 to the first input 14 of the meter 10, the number of periods, and through the adjustable delay unit 15 to the second input 16 of the switch 4. The adjustable delay unit can be, for example, a set of cables. Switched by electronic keys, and the control unit input is connected to the output of the phase delay meter within a period. An adder 17 entering the device is connected to the outputs of the phase meter 7 and the meter 10 of the number of periods. The control unit 18 controls the output to the control input of the meter 10, the number of periods, and the control S-, the input of the switch 4 and the control input of the phase meter 7. The control unit contains the master low-frequency generator (100-200 Hz) connected to the distributor of control signals. The device works as follows. On command from control unit 18, switch 4 connects the input of test quadripole 5 to the output of generator 1 of a sinusoidal signal, and the phase meter 7 measures the phase shift t between the input and input signal of the quadrupole. The code of the measured delay value within the period enters the control input of the variable delay unit 15 and reduces its delay by the value of t. The adjustable delay unit 15 and the delay line 13 are adjusted so that in the initial state, the signal is delayed by one period of the counting pulse. By the second command from the control unit, the switch 4 connects the input of the tested quadrupole through the adjustable delay unit 15 to the output of the pulse generator 12. According to the same command, the meter 10 of the number of periods counts the number (n) of counting pulses corresponding to the number of periods received by the meter during the time between the arrival at the first input 14 of the meter 10 and the number of pulse periods that passed through the delay line 13 from the output of the pulse generator (start pulse) and the pulse that came from the output of the tested quadrupole (stop pulse) to the second input 9 meter of the number of periods. From the phase meter within period 7 and meter 10 of the number of periods, measurement result codes are fed to the adder. The result of measuring the absolute value of the phase delay at the output of the adder is presented in the form f pT. t. Figure 2 shows the temporary rpavMi that explain the operation of the device. The first diagram shows the oscillograms of the output and output signals of the tested quadrupole when measuring the phase delay within the period Point O is the beginning of the reference, and point 0 is the end of the reference. The time interval between the points O and O is the time of the absolute phase delay of the tested four pole Tf. In this case, two periods of sinusoidal voltage (n-2) are laid in this interval; and another part of the period t. 2T + t. The second diagram shows the input and output signals of the tested quadrupole when determining an integer number of periods of a sinusoidal signal that fit into the interval of the absolute phase delay of the test four four-terminal. It can be seen from the diagram that §, the time interval between the input and output pulses (between the points O and J) fit three whole periods of sinusoidal voltage, i.e. The number of periods is not determined correctly. This noTjpMy occurs that the group phase v (j. Signal propagation speeds are not the same (vrp UV), and the number of periods for the phase delay is determined by a pulse signal that propagates through the tested quadrupole with a group velocity lower than the phase one. For most quadrupoles (in particular, for color television delay lines) the following conditions are fulfilled: Chrffg-- where t is the absolute group delay time; Cj. is the absolute phase delay time. The value of bt can take any value from O to T depending on the individual properties of the test quadrupole. (If conditions fail, you can lower the frequency of the sinusoidal signal.) From the diagram in Figure 2, we have iT +% p Cf ut + t + At and

the period number meter for this case will record the number of periods equal to 3..

Claims (2)

1.Ultraso, nic delay Line. National technical report, 1972, v.l8, No. 4 2. Pavlov V.A. Analysis of the method of co-trol of the delay time of ultrasonic lines on the sample. - Questions of radio electronics, ser. OT, 1971, issue 10, p.112. t . g niT- ti