A compact dual-passband filter using multilayer structure

This paper reports a compact dual-passband filter by using multilayer liquid crystal polymer technology. The investigated filter consists of two resonators on the middle metal layer, which can be independently designed for the two passbands. To achieve a compact size, the resonator for the upper passband is embedded in the resonator for the lower passband. Cross coupling between input and output ports is adopted in the design to improve the selectivity of the reported filter. Experiment is carried on to verify the predicted results and a well agreement is obtained. The proposed filter has a compact size and can be easily designed with flexible dual-passband response. It is attractive for the multiple bands communication system.