Tm Mode Of Ceramic Dielectric Duplexer

Since the 1990s, the demand for high-performance microwave filters and diplexers for both handset and base station applications has significantly increased for the rapid expansion of mobile communications. At the same time, the requirement for the performance of filters and diplexers is getting stricter, not only on excellent frequency selectivity, but also on their size, weight, temperature characteristics and cost.Due to a major breakthrough in ceramic material technology in the 1980s, people got interest in dielectric resonators and dielectric resonators filters which could be applied in a wide variety of microwave circuit configurations and their subsystems. So a number of new high dielectric constant materials with high quality factor and low temperature coefficients were developed. Especially, the ceramic dielectric duplexers applied to the RF front-end of base station have obtained more attention for their higher Q value, lower temperature coefficient and smaller volume, which is gradually applied to actual projects.The basic concepts of filter design and ceramic resonator theories are introduced in this paper, and a ceramic duplexer which works in the TM mode and can be used in the WCDMA system is designed. With the combination of theory and simulation, the physical dimension of the duplexer are given and the real product is produced. After tuning and testing, the performance of the duplexer can satisfy the design specification, and has obvious advantage compared with the coaxial cavity filter. Finally, some methods can be used to improve the performance of the duplexer were given.