A new method for tapered open-ended coaxial line probe in determining relative complex permittivity at radio and microwave frequencies

The measurement of complex permittivity of dielectric materials using coaxial line reflection methods at radio and microwave frequencies is of great interest. Peoples in basic and applied research areas as well as those in industry have an increasing requirement on the knowledge of the dielectric properties of materials. Based on coaxial line reflection methods, different probes employing various sizes and shapes are supposed and investigated[1]. Some of these methods have certain high requests on the configurations of the test samples. The dielectric properties of air and other materials are different and reflected microwaves are so sensitive to the dielectric properties of the materials under test that any small gap between samples and probes will cause measurement errors. The difficulties in preparing the samples lie in the necessity of precise cutting and machining. This cause researchers to find new probes which are easy to produce, have low requests on the preparation of samples and have tight contact between probes and samples[2∼4].