Study Of Spin Wave Linewidth Measurement System Of Microwave Ferrite Materials

The microwave ferrite materials (MWFM), which has been developed for morethan50years, are widely used in electronic devices. The power capacity of ferrite-basedhigh-power applications for radar system, such as circulators and phase shifters workingunder the condition of constant magnetization, is limited by the onset of first orderinstability. When the power value exceeds the threshold, the nonlinear excitation of spinwave under high power will take away the electromagnetic field energy. So themeasurement of spin wave linewidth is important to the design of high power devicesand ferrite materials’ research, though the cost of high power microwave source andrelated devices is very high. Therefore it’s helpful to setup an economy measurementsystem with wide range.In this thesis, I’ve studied the internal and foreign testing technology of the spinwave linewidth. After comparing a lot of testing methods, considering the systemrequirements, the final selection is the power inject into resonant cavity under parallelpump method. The test fixture is TE104mode rectangular cavity, through whichmeasures high power threshold level of spin wave nonlinear excitation, then spin wavelinewidth can be determined. The common method is using non-tunable cavity,adjusting the source to achieve resonance, then tuning the power level to search thestarting point of pulse distortion in order to determine the threshold level. In this system,the source frequency is fixed, the resonant cavity is tuned to the state of resonation, thepower is changed by the attenuator, and the static magnetic field is tuned to determinethe starting of distortion.This thesis, firstly, analyzed the mechanism of the nonlinear excitation of spinwave theory, and deduced the testing principle. Based on that, I designed andmanufactured a resonant cavity whose working frequency is tunable between9362±50MHz. Then I developed the key microwave devices of the testing system, such ashigh directivity directional coupler,0~40dB continuous tunable precision attenuator.According to the testing principle, I studied the high-power microwave sourcetechnology, and put forward the technology index of the source. Then I integrated subsystems, set up a high-power injection resonant cavity of testing spin wave linewidthof microwave ferrite polycrystalline material measurement system at room temperature.Finally, the sample is tested using the system, and the test results agree well with thestandard data. And the range of system error is provided by analyzing the influences tothe system, which caused by each error source.