Dual-Band Bandpass Filter Using Parallel Short-Ended Feed Scheme

In this letter, a compact dual-band (DB) bandpass filter based on parallel short-ended feed scheme is presented. Two sets of quarter-wavelength resonators operating at diverse frequencies are adopted to generate DB responses. A special feed scheme is proposed, which consists of two parallel short-ended strip branches. Each of them acts as a feed line of the respective resonator at one passband and a loading element at the other one. This scheme provides two independent transmission paths for RF signals. It is convenient to control the center frequencies of one passband, while the other's remains unchanged. Source-load coupling is also employed to create four transmission zeros close to the passband edges, resulting in high skirt-selectivity. To verify the proposed idea, a topology is demonstrated. The measured results exhibit good agreement with the full-wave simulation results.