SU1125556A1 - Device for measuring complex reflectance - Google Patents

Abstract

A DEVICE FOR MEASURING A COMPLEX REFLECTION RATIO, containing in series a first frequency synthesizer, a measuring probe section with a detector, a key and a power meter, characterized in that, in order to improve the measurement accuracy and expand the frequency range, a directional coupler is introduced, a second frequency synthesizer synchronizing the generator and the time master unit, while the output of the clock generator is connected to the inputs of the first and second frequency synthesizers and the time master unit a, the output of which is connected to the control input of the key, the input arm of the directional coupler is connected to the output arm of the measuring probe section, the output arm Q is the input for connecting the bipolar circuit under study, and the secondary arm is connected to the output of the second frequency synthesizer. Mh

Description

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The invention relates to radio metering technology and can be used to measure impedances at high and ultrahigh frequencies.

A device for measuring a complex reflection coefficient is known, which comprises a measuring generator connected to the measuring section and one or several communication probes lj,

The disadvantage of the device is low measurement accuracy.

The closest to the invention to the technical nature is a device for measuring the complex reflection coefficient, comprising a series-connected first frequency synthesizer, a measuring probe section with a key detector and a power meter 2.

The poorness of the known device are low measurement accuracy and a narrow frequency range.

. The purpose of the invention is to improve the measurement accuracy and frequency range spread.

The goal is achieved by the fact that a directional coupler, a second frequency synthesizer, a clock generator and a time reference unit are entered into the device for measuring the complex reflection coefficient, which contains the first frequency synthesizer connected in series, the measuring probe section with the detector, the KEY and the power meter, while the synchronizing generator is connected to the input of the first and second frequency synthesizers by the time of the master unit, the output of which is connected to the key control input, in The battery shoulder directional coupler is connected to the measuring probe vyhodnm shoulder section, an output port is input pfin connecting investigated two-pole and the secondary shoulder, connected to the output of the second frequency synthesizer.

The drawing shows a structural electrical circuit of the device for measuring the complex reflection coefficient.

The device contains the first synthesizer 1 frequency, measuring probe section 2 with a detector, power meter 3, directional coupler

And, the second frequency synthesizer 5, the key 6, the time setting unit 7, the synchronization generator 8, the two-terminal 9 under investigation, the computer 10.

The device works as follows.

The signals of the first and second synthesizers. Frequencies 1 and 5 are coherent, but differ by units or fractions of Hz. The signal of the first frequency synthesizer 1 is fed to the measuring probe section 2 with a detector. The signal of the second frequency synthesizer 5 is fed to the secondary arm of the directional coupler 4 and, reflected from the two-pole circuit 9 being studied, passes into the measuring probe section from the opposite side. The coherence of synthesizers 1 and 5 frequencies is provided by synchronization from the sigronizing generator 8. In addition, from the synchronizing generator 8, the signal is applied for a time to the specifying unit 7, generating rectangular pulses for opening the key 6. Due to the coherence of the signals of the first and second synthesizers 1 and 5, In the end section, which acts as an adder, a standing wave arises, similar to a standing wave in the measuring probe line. However, due to the inequality of frequencies, the wave shifts relative to the plane of the communication probe at a frequency equal to the frequency difference between the first and second synthesizers 1 and 5 frequencies.

Thus, by applying pulses with a frequency of a multiple and a higher difference frequency of the first and second synthesizers 1 and 5 frequencies, it is possible to measure the amplitude of the shifting standing wave in the measuring probe section, 2. In fact, a number of power measurements are crawling, equivalent to a power measurement with a multi-probe section. With the help of a computer 10, you can process the measurement result. The number of measurements for the period of the standing wave can be chosen arbitrarily,. The time of the period of the standing wave passing through the plane of the probe is CONNECTED to the period of the difference frequency of the frequency synthesizers. The duration of the pulse arriving from the time of the master block 7 on the key 6 is regulated. And much less than the period (period, difference frequency of the first and second synthesizers 1 and 5 frequencies).

The signal from the first synthesizer 1 frequency is U, V, 5in (y,), the signal from the second synthesizer 5 frequency is equal to Oj-Al ginCu i - Oil J then in the measuring probe section 2 the sum of two signals,

, n, 5iniu, t49) tV.2 rx5in a32 + (iL4Cpxl.,

where Gx is the modulus of the coefficient, the reflection from the two-terminal 9 under study;

Qx is the phase of the reflection coefficient from the two-port circuit under study 9.

 Under the condition of linear conversion: no frequencies are detected by the detector of the measuring probe section 2; the 3 power meter during each measurement captures the power

"1- With tGh 2 -t gtGh (9- -KHK where K is the transfer coefficient of the probes

connection, matching device and detector.

For various, we obtain a system of nonlinear equations of type (1) with four unknowns Vjf, Tjj j q) j ().

K values; Q; ut are determined before measurement, i.e. when calibrated, and memorized. By solving the required number of systems of equations of type (T), the total coefficient is determined.

reflection of G and its phase cpc. We present a rationale for obtaining a positive effect. The difference frequency between the first and second synthesizers 1 and 5 frequencies: iF depends on the discreteness of the frequencies of the frequency synthesizers, its smallest value can be 0.01 Hz. The frequency of the pulses applied to the time of the master unit 7 should be four times greater than iF, since This is equivalent to the use of a four-probe sensor when the power meter detects four times the power level (amplitudes of the standing wave) shifted relative to each other by i / 4, i.e. 90 °. For example, at a frequency of uF of 100 Hz, the phases of two coherent Sigdals change among themselves by 360 over time. If pulses with a 1/410 spacing interval are applied from the time of the master unit 7, then at the output of switch 6, four pulses will periodically lose, the amplitudes of which are proportional to the amplitudes of the standing wave in a single-probe measuring section, measured at 90 ° intervals, i.e. . D / 4. The error of setting the time interval of the time of the master block 7 is equal to the error with which the distance / 4 is determined, in a multi-probe sensor, between the communication probes. We estimate this error. The instability of the synchronization generator 8, for which the frequency and time standard is equal to io. where f {, is the frequency of 1 MHz or 5 MHz. Therefore, the instability of the frequency of the pulses of opening the key 6 is defined as

f 5-1P .. Phase pulse instability

40 36010 0.0018. Between the frequencies of coherent frequency synthesizers or oscillators covered by a phase-locked loop, the soup {their ratio is (0 for instability due to oscillator phase noise and having order 3. where f is 10 x i (v .J i.f, is the operating frequency of the oscillators.

Thus, the phase instability, causing the uneven displacement of the standing wave in a single probe measuring section 2

 2

 GHz, uq) +0.0021 Total error A (J uS + utp 0.005

When using four-probe sensors, the distance between the probes can be held no better than +0.2 mm, which is + 12- at a frequency of 20 GHz.

Thus, the amplitude of the standing wave curve in a single-probe measuring section, provided it is offset by the frequency difference of the frequency synthesizers, can practically be measured through any phase resolution no worse than 0.005. At a frequency of 20 GHz, With the use of four-probe sensors, this error will be +12 at the same frequencies

The frequency range has no practical limitation, since it is near 511255566

the displacement of the standing wave is determined by the amount of equation (1)

It is only the difference frequency syn-increase depending on the accuracy

frequency testers, or generators, measurements.

covered by the FAL ring 4. To single-zone- Application of the standard modern measuring instrument and special 5-meter measuring equipment

No requirements are imposed, since in the device, which provides for working errors, caused by the reflection in the set with other devices

MI from its entry and exit, exclude-through digital printing, allows automatization during calibration. Create a measurement and calibration process.

Claims (1)

A DEVICE FOR MEASURING AN INTEGRAL REFLECTOR COEFFICIENT, containing a first frequency synthesizer connected in series, a measuring probe section with a detector, a key and a power meter, characterized in that, in order to increase the measurement accuracy and expand the frequency range, a directional coupler and a second frequency synthesizer are introduced , a synchronizing generator and a timing unit, while the output of the synchronizing generator is connected to the inputs of the first and second frequency synthesizers and the timing unit, output One of which is connected to the control input of the key, the input arm of the directional coupler is connected to the output arm of the measuring probe section, the output arm g is the input for connecting the studied two-terminal device, and the secondary arm is connected to the output of the second frequency synthesizer. SO _nu 1125556>