New approach for configuring a parallel-planar dual-band bandpass filter by employing multilayered LTCC technologies

This paper describes a new approach for configuring a parallel-planar dual-band bandpass filter (DBPF) by employing multilayered low temperature co-fired ceramic (LTCC) technologies. This approach achieves the required frequency responses for the parallel-planar DBPF while retaining flexibility in selecting two center passband frequencies without the need for precise alignment between resonators in the filter packaging, which was required in a previously proposed parallel-planar DBPF. A cavity is implemented in the LTCC to avoid degradation in the unloaded Q-factors of the resonators. Evaluation results based on the frequency responses of 90 fabricated samples using a 0.8-/2.3-GHz band BPF show that there is only a slight deviation in the frequency responses of the parallel-planar DBPF.