Abstract
A new method based on direct frequency conversion is developed for measuring complex reflection coefficient of microwave two-poles. The method is based on the use of quadrature synchronous detection of the signal branched by omnidirectional probe with subsequent quadrature processing of the detected signal components. Such approach makes it possible to solve measuring task by simultaneously analyzing both amplitude and phase distribution of the field in transmission line which leads to redundancy. In addition, the use of direct frequency conversion provides the detection linearity in considerably higher dynamic range of the levels of the signal forwarded from the transmission line. So, both of these factors can improve the measurement accuracy. The method is performed by excitation of probing harmonic microwave oscillation in transmission line and formation of reference microwave oscillation with the same frequency. The reference signal and the signal branched from the transmission line by omnidirectional mobile probe are fed to the inputs the quadrature synchronous detector. At its outputs, I and Q components of the detected signal are formed. By means of these components, the amplitude and phase field distribution in the trans-mission line is obtained. It is followed by calculation of module and phase estimations using the expressions presented in the paper. The measurement result is obtained as arithmetic average of these estimations. A mathematical model of the proposed method is developed. The relations for the module and phase of the complex reflection coefficient are derived based on the analysis of both the amplitude and phase distribution of electromagnetic field in the transmission line. The paper describes the experimental unit in the form of vector measuring line that implements the quadrature method of measurement. The experimental analysis of the amplitude and phase distribution of the field in microwave path is carried out for standard loads with different parameters. Based on the analysis results, the estimations of measured parameters are calculated and measurement errors are defined. It is shown that highprecision measuring instruments can be designed using the proposed method.
Highlights
A new method based on direct frequency conversion is developed for measuring complex reflection coefficient
The method is based on the use of quadrature synchronous detection
"Современные проблемы радиоэлектроники и телекоммуникаций (РТ-2016), Севастополь, 14–18 ноября 2016 г
Summary
На выходах БКО получаем амплитудное U l и фазовое l распределения поля в ОЛП. Из (25) следует, что положение нулей фазового распределения не зависит от значения модуля , а определяется только координатой х, т. Для этого сначала следует в качестве нагрузки подключить образцовый короткозамыкатель, аргумент ККО которого кз , и зафиксировать положение нулей фазового распределения l0kкз , которые в соответствии с (26) будут расположены в точках с координатами l0kкз k 2. Запишем выражения для определения модуля и аргумента ККО на основе анализа амплитудного распределения для рассматриваемого случая:. Где lU – смещение минимумов амплитудного распределения при подключении в качестве нагрузки ОЛП образцового короткозамыкателя. Далее представлены избранные результаты экспериментального определения амплитудного и фазового распределений поля в ОЛП и результаты измерения модуля и аргумента ККО двух образцовых мер на частоте f 1.5 ГГц 20 см. 2 представлены графики амплитудного и фазового распределений поля при подключении к линии передачи образцового короткозамыкателя. В статье исследован квадратурный метод измерения комплексных параметров микроволновых двухполюсников, основанный на использовании квадратурного синхронного детектирования ответвляемого НЗ сигнала с после-
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