Free-space Test Methods For Microwave Dielectric Materials

Microwave dielectric materials have been widely used in the information and communication domain. Because of that knowing the dielectric materials'microwave characteristics is the most important factor in applications, it is very significant to measure the electromagnetic parameters of medium materials. Though the materials have been discovered since last century, many problems about such kind of complex medium still left for research. Recently, with the advancement of modern measurement, the improvement of the calculate quality, and the development of hyper-synthesis techniques and polymer engineering, many difficult problems can be solved successfully.In this paper, measurement techniques of both rigidity and soft medium materials have been systemic researched. Corresponding measurement has been proposed and many problems on dielectric materials'measurement, such as phase shift ambiguity problem, instability problem and so on, have been solved. The main research work includes:1. Through analyses of the correlative measurement technology and consideration of the characteristic of the measured materials, the free-space measurement method is established and the physical models are built. The transmission properties of electromagnetic wave in free-space are discussed, basing on Maxwell formulae and the constitutive relations of medium materials. The measured materials are regarded as two-port networks and through theory analysis, the relations between material parameters of medium and S-parameters are formulated.2. Free-space measurement system is established after theory analysis, and the calibration kits used in this system are fabricated. The TRL calibration technique and the time-domain gating feature of the network analyzer are used to eliminate the effects of undesirable multiple reflections. Automatic test software is complied to control the measurement system and calculate material parameters.3. Material samples are tested by this system and software in the frequency rang of 8-12 GHz. Finally, uncertainty has been analyzed and advanced methods for test...