RU1800390C - Method of measuring reflection factor - Google Patents

Abstract

The invention relates to radio engineering, in particular to a technique for measuring the reflection coefficient of various radio materials in a wide frequency band of the microwave range. SUMMARY OF THE INVENTION: the method is based on irradiating the test and reference samples with a swinging frequency signal, measuring at each frequency the amplitudes of the signals reflected by these samples, normalizing the amplitude of the signal reflected by the test sample by the amplitude of the signal reflected by the reference sample, and multiplying by the reflection coefficient of the reference sample, in addition, at each frequency, the phases of the signals reflected by both samples are measured, subtracted from the phase value of the signal reflected by the test sample, equal to the phase difference of the signal reflected by the reference sample and the phase of the reflection coefficient of the reference sample, the quadrature components of the signal with the corrected phase reflected by the test sample are formed, averaged over the frequency range equal to the ratio of the center frequency of the interval to the difference in the electrical path lengths at the central frequency, transmitted by the useful and interfering signal, and the amplitude and phase of the desired reflection coefficient are calculated. AND

Description

The invention relates to radio engineering, in particular to a technique for measuring the reflection coefficient of various radio materials in a wide frequency band of the microwave range. First of all, the invention can be used to measure the reflectance from local areas of radiolucent materials.

The purpose of the invention is to improve accuracy.

The application of this method can significantly reduce the influence of signals reflected from extraneous scatterers, and thereby increase the measurement accuracy

reflectance from the test sample over the entire frequency band.

The measurement of reflection coefficient by this method is carried out as follows.

First, the amplitude Ae and the phase c / b of the signal reflected from the reference sample installed at the place where the test sample will then be placed and having the corresponding shape (the phase is measured with respect to the phase of the reference signal) are measured at each frequency. Find the value of D (f, intended to adjust the phase of the signal reflected by the test sample, equal to

00

oh oh

CA) H O

the difference of the phase re and the known phase of the reflection coefficient of the reference sample

Dre re - pkos

Next, the amplitude Ac and the phase of the signal reflected by the test sample are measured. At each frequency, the pc phase is corrected by subtracting the value from it

fs pc -

The quadrature components are formed from the amplitudes and corrected phases of the received signal

Vk Ac COS p sc,; Vc Ac Sin (r ck

The quadrature components Vk and Vc are averaged over the frequency range A f equal to the ratio of the center frequency f of the interval to the difference in the electric path lengths A L at the frequency f traveled by the useful and interference signals

1

f + Af / 2

-DT I V / k d f

AT f-Af / 2 1 f + Af / 2

znr Iv / cdf

LT f-Af / 2

Note that the interval A f may or may not coincide with the swing band in which the reflection coefficient is determined, in particular, it may be substantially less than it.

Then, using the values of Vk and Vc, the amplitude q and the phase p of the desired reflection coefficient at the frequency f

„VvЈ + vi n

q Ae Q9 p arctg

where q3 is the known reflection coefficient of the reference sample.

This method of measuring reflection coefficient is implemented, for example, using a device whose structural diagram is shown in Fig. 1.

The device consists of a generator of oscillating frequency 1, first 2 and second 3 directional couplers, antenna 4, ampliometer 5, correction unit 6, memory unit 7, quadrature component unit 8, integrator unit 9, calculator 10, recorder 11 and control unit 12. The number 13 designates the test sample, and the digital 14 indicates the constant diffuser.

The device operates as follows.

The signal from the oscillating frequency generator 1, passing through the first 2 and second 3 directional couplers, is fed to

antenna 4 and is radiated. The emitted signal falls on the test sample 13 and partially falls on an extraneous diffuser (to measure the signal reflected by the reference sample, it is installed in place of the test sample). The signal received by antenna 4, due to reflections, passes through the second directional coupler 3 to the first input of the ampliometer 5. At the same time, the first directional coupler 2 branches out part of the signal of the oscillating frequency generator 1 to the second input of the ampliometer 5, forming a reference signal. Measured in an amplitude meter 5 amplitudes and

the phases of the signal through the correction block 6 are supplied to the block of quadrature components 8. In the correction block 6, the phase is corrected by the correction signal coming from the memory block 7. The correction signal is accumulated when measuring reflections from the reference sample. In particular, a metal sample for which q3 1, r.oe -

in block 8, quadrature components are formed from the amplitudes and corrected phases of the received signal, which are averaged (integrated) in the block of integrators 9. The integrator unit 9 is connected to a calculator 10, in which the amplitude and phase of the reflection coefficient at each given point f of the frequency sweep are calculated from the results of averaging the quadrature components. In block

and the found reflection coefficient values are recorded. The synchronization of the blocks of this device is carried out by the control unit 12. This method allows

increase the accuracy of measurement of reflection coefficient values and thereby expand the dynamic range of its measured values.

Claims (1)

The claims A method for measuring the reflection coefficient of radio material based on irradiating the test and reference samples with a swinging frequency signal, measuring at each frequency the amplitudes of the signals reflected by the tested Ac and the reference Ae samples, normalizing the amplitude of the signal reflected by the test sample by the amplitude of the signal reflected by the reference sample, and multiplying on the reflection coefficient of the reference sample de, characterized in that, in order to improve accuracy, in addition, at each frequency, the phases of the signals reflected obtained by the test pc and the reference samples, subtract from the phase value of the signal reflected by the test sample, the value equal to the phase difference of the signal reflected by the reference sample and the phase of the reflection coefficient of the reference sample, form the quadrature components of the signal with the corrected phase reflected by the test sample, averaged them in the frequency range A f equal to the ratio of the center frequency f of the interval to the difference of the electric path lengths L L at the frequency f traveled by the useful and interfering signals, and the amplitude q and the phase p of the desired reflection coefficient is determined by the formulas q VVi + V§ qa: Vc p arc tg, Where Vk 1 f + Af / 2  -TGT- / Ac COS pc - (( iA T g L / o f - Af / 2 f + Af / 2 Vc  -T-f- / Ac Sin pc - ((-) d f; T f-Af / 2 Af + ЈT