Research And Design Of Measuring Device Of Complex Permeability Of Magnetic Film At High Frequency

The use of magnetic thin film materials for the fabrication of high frequency and microwave devices is a hot topic in recent years.Magnetic thin film materials can operate in the frequency range of several MHz to tens of GHz.The use of magnetic thin film materials can greatly improve the performance of components and reduce the volume of components.At the same time,magnetic thin film devices are easier to be integrated with integrated circuit processes.Therefore,the research of magnetic thin film devices has attracted the attention of the industries.The permeability of ferromagnetic thin film materials is a very important parameter for designing and developing RF components such as inductors,resonators,transformers,and circulators.In order to accurately design the above devices,it is necessary to accurately measure the permeability of the magnetic film at high frequencies.In light of this,there is a need to study equipments for measuring the permeability of magnetic thin films that can be able to function at high frequencies.So far,the permeability measurement techniques have been classified into two main groups.The first one is utilizing the magnetic flux variations in the pick-up coil impulsed by an external electromagnetic field.The second method is utilizing transmission line perturbation including microstrip,coplanar waveguide and coaxial transmission line.This thesis has carried on relevant research and design to the measurement device that the above-mentioned two kinds of measuring techniques has produced,the main content includes three major parts:Firstly,the test fixture of the short circuit microstrip line method is introduced.The calculation formula of the complex permeability of the corresponding fixture is deduced from the transmission line theory and the equivalent impedance method.The fixtures were simulated with HFSS to study the effects of various dimensions of the fixture.Then,the dimensions were modeled and determined,and the permeability was calculated using simulation data to verify the effectiveness of the fixture.The corresponding test fixture were processed,put the 33 nm NiFe thin film into the test fixture,and its permeability was calculated.Then,the dual-coil model composed of traveling wave drive coils is introduced first,and a traveling wave drive coil that meets the actual requirements is designed.Afterwards,a variety of combinations of induction coils and output structures were studied.Finally,a combination of a minimal loop induction coil structure and a microstrip line output was used.This combination has high sensitivity in both low and high frequency bands,and reduces the difficulty of design,processing,and assembly.After using the simulation data to calculate the permeability to verify the effectiveness of the fixture,the corresponding physical objects were processed.It was used to measure the 2500 nm Ni Fe film,and the permeability of the Ni Fe film was calculated.Finally,the structure of the shielded loop induction coil is studied and designed,and how it can counteract the influence of the electric field is analyzed.The problem of high signal-to-noise ratio at low frequency band and small size of induction coil in the test of the simple loop induction coil is improved,so that the lowest measurable frequency can reach several tens of MHz.