LTCC Wideband Bandstop Filter With Controllable Bandwidth Using Internal Coupling

A compact low temperature co-fired ceramic (LTCC) bandstop filter (BSF) with controllable bandwidth is presented in this paper. Compared with the conventional method, the internal coupling between resonators is introduced in the structure to split one zero into two, namely transmission zeros pair (TZP). Then the bandwidth is flexibly controlled by adjusting the internal coupling strength. Besides, multiple transmission poles (TPs) are generated to enhance the roll off while maintaining the stopband performance. For demonstration, a LTCC wideband BSF is implemented and measured. Both TZP and multiple TPs are observed with compact circuit size. Good agreement between the simulated and measured results verifies the proposed method.