Microwave Measurement And Application Of BST Dielectric Properties At X-band

With the development of high-frequency and high-speed of the communications device, microwave dielectric materials have been widely used. At the same time, more and more attentions have been paid to the accurate measurement of the microwave performance of the high-k dielectric materials so that it can be applied for the design of the device.In this paper , the improved methods for microwave performance measurement of the dielectric permittivity and tuning properties of BaxSr1-xTiO3 (BST) were investigated and established at the microwave frequencies of X-band(especially at the main frequency of 10GHz). The microwave properties of BST ceramic and film were measured by the methods. The microwave phase shifting devices were designed and fabricated basing on the measurement results and their performances were also tested.First, the microwave resonance method combined with the non-resonance method is used for the measurement. They include cavity perturbation method, rectangular phase shifter method and coplanar waveguide method. The traditional cavity perturbation method was improved for the high permittivity and loss tangent measurement of the dielectric materials at X-band. The rectangular waveguide phase shifter was designed especially for the tuning properties measurement of the dielectric ceramic for the voltage can be easily put on. The 1/4 wavelength matching was designed to reduce the return loss during the testing process. The coplanar waveguide for TRL test method were improved for the use of BST film permittivity and tuning property measurement. The CPW devices were fabricated on the sputtered thin-film electrodes by lithography and they are tested at the same time. All the above methods constitute the test system for the dielectric and tuning properties measurement of the dielectric ceramic and film.Then, the combination of microwave network analyzer and the RF probe station were used for the measurement of the devices basing on the BST ceramic or film. And the material properties of BST were derived from the results of the devices performance. The analysis of the test errors caused by the test system, the devices and so on were taken into consideration to make the results more accuracy. The errors of the results were determined.Finally, the software of ADS was used for the simulation and design of BST coplanar waveguide phase shifter loading with inter-digital capacitor. The phase shift of 25 degrees per centimeter was got. And this finally determined the device requirement of the BST material and the how can the device can be improved.