RU2069862C1 - Method for determination of s-parameters - Google Patents

Abstract

FIELD: radio engineering. SUBSTANCE: invention may be used for determination of S-parameters of SHF equipment. While determining S parameters of SHF equipment one divides SHF signal into two parts: first one is fed to measured SHF equipment, low frequency signal passed or reflected from it is modulated by voltage of frequency Ω₂, second part of low-frequency signal is modulated by voltage of frequency Ω₁≠Ω₂, both components are summed up, difference frequency signal and signals with frequencies 2Ω₁ and 2Ω₂ are isolated and their amplitudes are measured. Sought-for S-parameters are found by amplitudes. EFFECT: expanded frequency range. 1 dwg

Description

 The invention relates to techniques for measurements at microwave frequencies and can be used to determine the S-parameters of microwave devices.

 The purpose of the invention is the expansion of the frequency range.

 The drawing shows a structural electrical diagram of a device that implements the proposed method.

 The device comprises a generator 1, a directional coupler 2 of the reference channel, a directional coupler 3 of the reflected wave of the measuring channel, a directional coupler 4 of the transmitted wave of the measuring channel, a measured four-terminal 5, the first and second matched loads 6 and 7, switch 8, the first and second amplitude modulators 9 and 10, mixer 11.

 Method A.S. Elizarova definition of S-parameters is implemented as follows.

The output signal of the generator 1 is divided using a directional coupler 2 into two parts, one of which is a reference signal, and the second is a measuring signal. In turn, the measuring signal, partially reflected from the measured four-terminal 5 and propagating through it, is converted into the output signals of the secondary channels of the directional couplers 3 and 4. These signals with the help of the switch 8 are alternately supplied together with the output signal of the reference channel to the mixer 11. In this case reference channel output signal modulated in amplitude with the first amplitude modulator 9, a low frequency voltage of frequency Ω _1, and the output signal selector 8 - voltage frequency Ω ₂ using a orogo amplitude modulator 10.

где α₁ и α₂ коэффициенты передачи детекторов амплитудно-фазового дискриминатора (АФД);
М₁ и M₂ коэффициенты амплитудной модуляции сигналов в опорном и измерительном каналах соответственно;
К₁.K₄ модули суммарных коэффициентов передачи каждого пути, по которому СВЧ сигнал от места разветвления опорного и измерительного каналов проходит к соответствующему детектору АФД;
E_o амплитуда поля в месте разветвления опорного и измерительного каналов;
K_yc1.K_yc4 коэффициенты усиления селективных усилителей напряжений U_1вых. U_4вых;

модуль и фаза измеряемого S-параметра;
Φ_н фазовый сдвиг, учитывающий неидентичность фазочастотных характеристик опорного и измерительного каналов;
Δ фазовый сдвиг, учитывающий несинфазность и неквадратурность деления сигналов в АФД.The output measuring signals can be written as follows:

where α ₁ and α ₂ transmission coefficients of the detectors of the amplitude-phase discriminator (AFD);
M ₁ and M _{2 the} coefficients of the amplitude modulation of the signals in the reference and measuring channels, respectively;
To ₁ .K ₄ modules of the total transmission coefficients of each path along which the microwave signal from the branching point of the reference and measuring channels passes to the corresponding AFD detector;
E _o the field amplitude at the branching of the reference and measuring channels;
K _yc1 .K _yc4 gains of selective voltage amplifiers U _1out . U _4out ;

module and phase of the measured S-parameter;
Φ _n phase shift, taking into account the non-identical phase-frequency characteristics of the reference and measuring channels;
Δ phase shift, taking into account the non-phase and non-squared signal division in the AFD.

и Φ_iк, зная только U_1вых, U_3вых и U_4вых. Отсюда следует, что АФД, который имеется в устройстве, реализующем способ (1), может быть заменен смесителем 11. Отпадает необходимость в квадратурном делении СВЧ сигнала, имеющем место в АФД, и применении для этой цели соответствующих гибридных соединений. Измерительный тракт анализатора цепей предельно упрощается.An additional measurement of U _4out allows _you to calculate

and Φ _iк , knowing only U _1out , U _3out and U _4out . It follows that the APD, which is available in the device that implements method (1), can be replaced by a mixer 11. There is no need for quadrature division of the microwave signal, which takes place in the APD, and the use of corresponding hybrid compounds for this purpose. The measuring path of the network analyzer is extremely simplified.

Из сопоставления (1), (3) и (4) с (5) (7) видно, что в (5) (7) принято α₁=α. Кроме того, различие K_yc1, K_yc1 и K_yc4 может быть сделано пренебрежимо малым за счет предварительной калибровки анализатора и на суть способа не влияет. Поэтому в выражениях (5) (7) фигурирует результирующий коэффициент передачи К_y аналоговой части устройства обработки и вычисления анализатора. Эта обработка производится по следующему алгоритму.The measurement of the amplitudes of the signals U _1out , U _3out and U _{4out is} accompanied in modern network analyzers by analog-to-digital conversion for subsequent calculation using the microprocessor of the values of S-parameters. The ADC input voltages are, as a rule, constant voltages obtained by synchronously detecting the signals U _1out , U _3out and U _4out . Therefore, we will operate with numerical data arrays corresponding to the following ADC input voltages:

From a comparison of (1), (3) and (4) with (5) (7), it can be seen that α ₁ = α is taken in (5) (7). In addition, the difference between K _yc1 , K _yc1 and K _yc4 can be made negligible due to preliminary calibration of the analyzer and does not affect the essence of the method. Therefore, in expressions (5) (7), the resulting transfer coefficient K _{y of the} analog part of the analyzer processing and computing device appears. This processing is performed according to the following algorithm.

2. Полученный массив (8) и исходный массив, соответствующий напряжению (5), позволяют сформировать два дополнительный массива

3. Если теперь разделить (10) на (9), то в соответствии с общеизвестным тригонометрическим соотношением

откуда сразу определяем

причем значение Φ_н известно по результатам предварительной калибровки анализатора. Необходимо обратить внимание на знак функции tg(Φ_iк+Φ_н)/2,, чтобы не допустить неоднозначности при вычислении Φ_iк. Наиболее простым способом является вычисление знака приращения напряжения (5) при переходе от одной частотной точки к другой в процессе качания частоты анализатора. Это вычисление осуществляется с помощью специальной подпрограммы и основано на однозначном соответствии знаков функций cosΦ и tgΦ/2..1. From the initial data arrays corresponding to the voltages (6) and (7), an auxiliary array is formed

2. The resulting array (8) and the initial array corresponding to the voltage (5) allow the formation of two additional arrays

3. If we now divide (10) by (9), then in accordance with the well-known trigonometric relation

from where we immediately determine

and the value of Φ _{n is} known from the results of preliminary calibration of the analyzer. It is necessary to pay attention to the sign of the function tg (Φ _iк + Φ _н ) / 2, in order to avoid ambiguity in the calculation of Φ _iк . The simplest way is to calculate the sign of the voltage increment (5) during the transition from one frequency point to another during the sweep of the analyzer frequency. This calculation is carried out using a special subprogram and is based on the unique correspondence of the signs of the functions cosΦ and tgΦ / 2 ..

еще один вспомогательный массив

5. Если теперь перемножить полученный массив (15) и исходный массив, соответствующий напряжению (5), получим массив данных, соответствующий сигналу (2). Действительно, массив (15) задает функцию (14), т.е. результат перемножения дает

Таким образом, получили массив данных (16), соответствующий квадратурному сигналу (2) и позволяющий вычислить

то стандартному алгоритму

причем знаменатель (17) известен по результатам предварительной калибровки анализатора.4. The data arrays (11) and (12) allow not only to calculate the argument of the measured S-parameter, but also to generate, using the well-known trigonometric relation

another helper array

5. If we now multiply the resulting array (15) and the original array corresponding to the voltage (5), we obtain the data array corresponding to the signal (2). Indeed, array (15) defines function (14), i.e. multiplication result gives

Thus, we obtained a data array (16) corresponding to the quadrature signal (2) and allowing us to calculate

then the standard algorithm

the denominator (17) is known from the results of preliminary calibration of the analyzer.

Claims (1)

The method for determining the S-parameter, which consists in dividing the continuous microwave signal into two parts, the first of which is fed to the measured four-terminal network, is modulated with a low-frequency voltage of frequency Ω ₁ , the transmitted or reflected signal from it, modulate the second part of a continuous signal with a low-frequency voltage of frequency of ₂ ≠ Ω ₁ , summarize both components, extract the signals of the difference or total frequency and measure their amplitude, measure the amplitudes of the signal with a frequency of 2Ω ₁ , which normalize the amplitude of the signals of the difference or mmar frequency, and by calculation determine the desired S-parameters, characterized in that, in order to expand the frequency range, an additional signal of frequency 2Ω _{2 is} isolated, its amplitude is measured, which is taken into account when determining the desired parameters.