Investigation Of Measurement For Microwave Electromagnetic Parameters Of Nanostructural Magnetic Thin Films By Cavity Perturbation Method

With the widespread use of microwave-absorbing materials in the field such as radar microwave stealth technology, electronic countermeasure, microwave communication and electromagnetic compatible, it becomes an important issue to research and develop microwave-absorbing materials for the demand above. FeCo-based alloy nano-granular films and nano-multilayer films are more accounted for their high permeability and high magnetic loss under microwave frequency to realize broadband absorbing of microwave. Therefore, the measurement of microwave electromagnetic parameters has become one of the leading research problems and hot spots of scientific tasks in the field of nanostructrual thin film characterization.After a series of electromagnetic parameters measurement methods of thin film were critically reviewed at home and abroad in this thesis, cavity perturbation method was ascertained the selection to make the simultaneous measurement of the real and imaginary components of permittivity and permeability for the film studied. The equations between the microwave permittivity and permeability of thin films and the resonance frequency and quality factor were determined by the cavity perturbation theory and Maxwell equations.Design principle of rectangular cavity measurement jig used at different frequency points was put forward in this paper. Under the guideline of principle, the self-design and self-made reflex rectangular cavities whose resonance frequencies are 2 GHz,4 GHz,6.5 GHz,10 GHz can be used for the requirements of attainable precision measurement.Hence, the automatic measurement systems used at different frequency points with GPIB bus mastering consisted of an Agilent 8722 ES Vector Network Analyzer, personal computer, the resonant cavities and an 82357 USB/GPIB cable were set up. Furthermore, automatic measurement software modularization program is developed extensively by virtual instrumentation. And then, the complex electromagnetic parameters of thin films were measured successfully by cavity perturbation method at different frequency points. The measurement results can describe the microwave properties of magnetic films more comprehensive. The resonant cavities were fabricated as prototype measurement fixtures with the help of Ansoft-HFSS. Fabrication results meet with the measurement results approximately. Furthermore, the process of the measurement is also simulated to testify correctness of the measurement method.A series of FeCo-based nanostructural thin films by magnetron sputtering in different substrate with micron scale in thickness were measured at different frequency points by our developed automatic system and obtained also the valuable results. Thus, an analysis of the main measurement factors on the currency of microwave properties is presented. The methods of reducing errors that result from these factors have improved the precision of the measurement.