| Summary: | 碩士 === 華梵大學 === 電子工程學系碩士班 === 93 === ABSTACT
The purpose of this thesis is on "the design of six-port reflectometers suitable for using in the automatic impedance matching circuit". It is well known that this reflectometer can accurately calculate the reflection coefficient of the device under test(DUT) by simply using the measured microwave powers. The traditional reflectometer uses more microwave power to do the reflection coefficient measurement job. Therefore, there is less transmitting to DUT. This type of reflectometer is not suitable to corporate with tunable impedance matching circuits to form a high efficiency automatic impedance matching circuit.
Several six-port reflectometers, which have appeared in documents, are modified in this thesis to meet the research purpose requirement. These six-port reflectometers include: (1) the network made by a coupler and four quadrature hybrids, (2) the network made by a coupler and four quadrature hybrids and a T power divider, (3) the network made by a symmetrical five-port ring structure and a coupler, (4) the network built from three couple lines. The computer optimization method is used to calibrate these reflectometers. The system constants of these reflectometers are successfully obtained from calibration. Simulation shows that all these four reflectometers can get satisfactory measurement results.
This research has successfully combined the six port network and power measurement equipments to form an automatic reflectometer. By using the personal computer(PC) to read the output power data from measurement requirements, the reflectometer can automatically calibrate the system constants. These constants are used to automatically calculate the reflection coefficient of DUT. Experimental results verify that the four reflectometers all can measure the accurate reflection coefficient in the designed frequency band. They are all suitable for constructing the automatic impedance matching circuit. Comparisons between these four reflectometers are also made according to experimental results in the thesis.
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