Ultra Wideband Ferromagnetic Resonance Linewidth Measurement System Based On Coplanar Waveguide

Under the background of the rapid rise of information technology,the working frequency of major passive devices and circuit systems has gradually shifted to a higher range.In microwave and millimeter wave band,ferromagnetic materials,including magnetic films and microwave ferrite,have been widely used in many fields.Such as magnetic sensor chip,Magnetoresistive Rrandom Aaccess Mmemory(MRAM)chip,Low Temperature Co-fired Ceramic(LTCC)magnetic material belt,etc.However,with the increase of frequency,the quality of ferromagnet must be improved accordingly,such as low losses,low radiations,strong anti-interference and so on.Among them,the microscopic process of ferromagnetic material loss is mostly characterized by ferromagnetic resonance(FMR);The macroscopic manifestation is ferromagnetic resonance linewidth(?H)Parameter,which is used to directly measure the magnetic loss of magnetic materials.Therefore,it is of great significance to accurately measure the ferromagnetic resonance linewidth of ferromagnetic materials.The current measure methods are mostly transmission line perturbation methods,including resonant cavity method and planar transmission line,the former has a higher quality factor and the latter has a larger test range.In addition,the former can only be measured at a single point frequency,and as the test frequency rises to the millimeter waveband,the waveguide transmission line itself and the fabrication of the sample become difficult.Therefore,based on the framework of VNA-GCPW(Vector Network Analyzers-Grounded Coplanar Waveguide),this thesis independently designs,builds and finally realizes a set of FMR highly automated test system in the range of 5 GHz-67 GHz.The main work and achievements are as follows:1.Based on the test requirements,a grounded coplanar waveguide for in-plane and out of plane ferromagnetic resonance linewidth test is simulated and fabricated to ensure that it has low insertion loss in the range of 67 GHz to ensure that the ferromagnet can fully resonate.At the same time,the wiring mode is adjusted to ensure that the ferromagnet can resonate under the action of two magnetic fields.Based on the grounded coplanar waveguide,a set of mechanical fixture is designed to fix the waveguide,coaxial line and Hall probe.The design of the fixture enables the waveguide to rotate 360 degrees,so as to realize two different ways of testing in-plane and out of plane.2.Through Lab VIEW language,the serial communication between computer and vector network,power supply and Hall probe is established,and a set of test software is written to realize the automation of test and data processing.The automation of testing relies on computer preset parameters and local commands to form instructions and instruments for signal reception and transmission.The automation of data processing mainly includes two aspects: one is the de embedding algorithm,which is realized by successively testing the scattering parameters of no-load grounded coplanar waveguide and loaded grounded coplanar waveguide,as well as the algorithm in the software;The second is Lorentz fitting,which automatically imports the data into origin and completes the fitting after the test is completed through the joint operation of Lab VIEW and origin.After the automatic test system is built,good absorption curves are obtained through different samples tests.Finally,the field distribution of GCPW transmission line structure and the potential test feasibility range are studied.