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.