Double Magic T And Double-crystal Detector-based Multi-state Reflectometer

The technology development of microwave measurement is be closely linked with the development of microwave devices, furthermore microwave measurements with high precise and speediness always depend on the research and exploitation of precise devices. Six-port measurement technology based on powers is a kind of effective method which is able to precisely measure the reflection coefficients of microwave units. At the same time this technology can be widely applied in many domains, such as microwave measurement, security detection, industrial detection, and so on. Therefore, the six-port measurement technology has been focused on by many researchers in many countries since it was proposed, and has become one of the most important tools for microwave measurement. Speaking from comprehensive meaning, study on multi-state reflectometer composed of double magic-Ts, which is based on six-port principle, to some extent has use value and practical significance, for this device equipped with computer and interface circuit can collect and process data with automation, and it can measure with half-automation measurement and automation measurement the microwave parameters of microwave units, such as complex reflection coefficients, and so on.In the first three chapters this paper expounds fundamental things, such as the realistic significance of six-port measurement technology, research status in quo about this work at present, tasks I have done, mathematics knowledge used in this process, fundamental theories and overview of this technology. In the forthchapter this paper expounds the correction methods of diode detectors, when signal is little three power-indicating ways- voltage values detected by diode detectors just being used as powers, the method of power-attenuating correction, and the method of straight correction - are mentioned and compared, the conclusion derived from comparison is that when signal is little and voltage values detected by diode detectors are just used as powers, error range caused by this will be so little to be accepted, at the same time the paper highlights the method of straight correction as the most ideal correction method of diode detectors. In the last two chapters this paper expounds designing scheme of multi-state, methods of system calibration and results of practical measurement. As to the designing scheme of multi-state reflectometer, the paper expounds components of very part and corresponding circuits. In the sixth chapter, based on both the absolute power method and the relative power method suggested by six-port theories, the paper deduces the corresponding methods to be accommodated to the multi-state reflectometer. while based on the calibration methods above, two power-indicating ways - power method and diode-detector corrected online - are applied to practical measurement, at the same time practical measurements are executed for proof-test under different frequencies, at last geometry interpretation of calibration method is applied to elementary research on the relative location relationship of state circles, and a parameter to evaluate measurement data is pointed out.Emphases of the paper's content are rendered as below:1. the multi-state reflectometer is composed of the common microwave devices(including Magic-T, diode detector, matched load, changeable short device, and so on) in the lab, with the help of computer data are processed, and microwave measurements and data analyses are performed with more automation, speediness and ease to operate. The precisions of measurement dataare much high, and much measurement data with reference value are collected, so the paper can be regarded as a handbook for engineering and technology persons.2. The multi-state reflectometer uses diode detectors as power indicators displacing powers, and ensures that precisions of results with diode detectors are much less than those of results with powers. As to the correction methods of diode detectors, this paper has made comparatively systematic and overall research, compared and analyzed power-attenuated correction method and straight correction method to effectively improve the simplicity and exactness of correction and system calibration.3. As for multi-state and six-port circuitry constructed by double magic-Ts, practical measurements are performed under different frequencies within working frequency scope of double magic-Ts, law of changing precision are researched under matched frequency and other frequencies of magic-Ts. The conclusion that the measurement precision of this system will be close to or even reach the ideal performance indices of six-port measurement system has been made.4. Based on absolute power method and relative power method suggested by six-port theories, this paper deduced the corresponding methods to suit the multi-state reflectometer. At the same time in the relative power method, though presumption that some system constants keep fixedness when system state will be changed is made, the measurement precision is obviously better than those of the relative power method.5. Based on the geometry interpretation of six-port measurement technology, this paper has analyzed the self character of multi-state reflectometer constructed by double magic-T through the location relationship of statecircles. At the same time based on position relationship of centers of state circles, this paper introduces an evaluating parameter for measurement data, which enables us to effectively evaluate measurement data to ensure high precision of system measurement.Innovations of the paper are rendered as below:1. Online correction method of critical detector is used, practical measurements are performed with multi-state reflectometer constructed by double Magic-Ts, the precisions of measurement results are much high.2. the absolute power method and the relative power method are reduced to suit the multi-state reflectometer in accordance with many kinds of system calibration methods, based on the geometry interpretation of calibration methods a datum-evaluating parameter is provided.Some shortcomings can also be found in this paper, such as just two system calibration methods, just the changeable short device used as a tested load, and no other practical measurement involved.