Research On Measurement System Of Ferromagnetic Resonance Linewidth By Shorted Microstrip Line Method

Microwave ferrite devices are widely used in modern communication field, the measurement of performance parameters of ferrite materials is becoming more and more important. The purpose of this paper is to realize the broadband measurement of the ferromagnetic resonance linewidth. Based on the analysis of traditional measurement method and broadband measurement permeability method, a shorted microstrip line is used as a test fixture and measurement system is built by vector network analyer. The ferromagnetic resonance linewidth ?H? of rectangular yttrium iron garnet(YIG) ferrite samples is measured by this measurement system.Based on the transmission line equation and the Maxwell equation, the expressions of S parameters and the equivalent complex permeability ?e are derived. By the method mentioned above, the ?H?=??/? is obtained, where ?? is the full-width at half-maximum(FWHM) for the peak in the imaginary part of complex permeability at resonance. The initial size of shorted microstrip line fixture is designed by the principle of impedance matching, and the size is simulated and optimized by Ansoft-HFSS. Finally, in order to achieve a convenient measurement, the man-machine interative visual graphical interface is complied with Labview.YIG ferrite samples with 0.24 mm thickness are measured in the frequency range of 0.01-5 GHz. It is shown that when the static magnetic field 2120 Oe is applied, the test results ?H? is 57.26 Oe which is basically consistent with the simulation results 57.02 Oe. It also analyzes the influence factors on the measurement results. The calibration surface of vector network analyzer is extends to the microstrip line port, which can avoid the fixture internally generated size resonance effect resonance frequency discrimination. The sample surface after polishing, the surface pits decreased, and ?H? is smaller than before polishing. The molding pressure of sample is greater, the smaller ?H?. The thickness of sample is thicker, the smaller ?H?.A shorted microstrip line method can implement a broadband measurement by sweep frequency and measurement device is fast, easy to operate because the test sample can be easily prepared. This method is also suitable for larger size samples with narrow linewidth, and realize the measurement of rectangular sample at low frequency.