Construction And Improvement Of A Broadband Ferrite Ferromagnetic Resonance Linewidth Measurement System

Microwave ferrite is widely used in electronic information systems in the fields of radar,communications,navigation,telemetry,and other fields due to its unique rotational magnetism.Ferromagnetic resonance(FMR)linewidth,as an important parameter characterizing the magnetic loss of gyromagnetic materials,has a decisive impact on the performance of microwave ferrite devices operating at or near a certain microwave frequency.With the continuous development of electronic information systems towards integration and high frequency,higher requirements are put forward for the high frequency characteristics of microwave ferrite.Therefore,it is required that the ferromagnetic resonance linewidth of all band gyromagnetic crystal materials be measurable and controllable.Currently,there is no complete theoretical system for measuring ferromagnetic loss of millimeter wave band microwave ferrite electromagnetic materials in the world.With the development of new materials and devices in millimeter wave band,there is an urgent need to achieve the measurement of ferromagnetic resonance linewidth in millimeter wave band at home and abroad.This thesis builds and improves a broadband ferrite ferromagnetic resonance linewidth measurement system based on the original research results of the research group.The test system is built based on the Vector Network Analyzer(VNA),and the ferromagnetic resonance linewidth measurement is performed using the principle of resonant cavity perturbation method.Based on Labview and Matlab,automated testing software and data processing software were written to automate the measurement process and improve measurement accuracy.When the measurement frequency is below 40 GHz,the traditional method of "loading through a dielectric rod" is used for sample loading.Five resonators suitable for different frequency bands are used to achieve ferrite FMR measurement in the 2 to 40 GHz frequency band;When the measurement frequency is above 40 GHz,a method of loading a sample through a dielectric sheet is proposed.After verifying the feasibility of this method,the measurable frequency of ferrite ferromagnetic resonance linewidth is successfully increased to 65.12 GHz;And four different systems of ferrite samples,YIG,Ni Cu Zn,Li Zn,Ba Ni Fe O,were prepared to verify the functionality of the measurement system.The ferromagnetic resonance linewidths of the four systems of ferrite samples were measured at 65.12 GHz,which were 214.67 Oe,537.24 Oe,722.56 Oe,and1645.34 Oe,respectively.Finally,a fast detachable waveguide structure for ferrite FMR measurement is proposed,which further improves the measurement convenience of the method of loading samples through dielectric plates and provides a theoretical basis for achieving higher frequency band ferrite FMR measurement.