Dual-band bandpass filter using embedded short-circuited resonators in the open-loop c-shape resonator

This paper presents a planar dual-band bandpass filter based on a novel embedded resonator concept. The proposed filter employs four sets of resonators embedded inside the conventional open loop resonator to generate two passband responses without affecting the filter´s size. Two pairs of embedded resonators are electromagnetically cross coupled to generate the required passbands. The proposed technique provides sufficient degree of freedom to control the centre frequency and bandwidth of the two passbands. The four transmission zeros created between the passbands results in high skirt selectivity, sharp frequency cut-off, high isolation and low passband insertion-loss. The proposed technique was verified practically, and the design methodology and experimental results are presented.