MINIATURIZED MICROSTRIP BANDPASS FILTER USING COUPLED SCRLH ZEROTH-ORDER RESONATORS

摘要

A novel miniaturized microstrip bandpass filter (BPF) has been proposed by using coupled simplified composite right/left-handed (SCRLH) zeroth-order resonators (ZORs). The SCRLH ZOR consists of microstrip high/low-impedance short-line elements, grounded stub, and transmission line sections. Being one of the artificial metamaterials, the SCRLH ZOR resonates when the phase constant equals to zero. Compared with the conventional half-wavelength resonator, the superiority of the proposed ZOR mainly lies in its compact size. In addition, it is easy to tune the zeroth-order resonant frequency, thanks to its simple structure and easy fabrication. In this article, the performance and design of the novel ZOR is first studied in detail. Then, the ZOR is exploited to devise a three-order Chebyshev coupled microstrip BPF. Different coupling schemes are adopted, including interdigital capacitor coupling for the interstages and aperture-backed dual-finger parallel-coupled line structures at the terminals, thus, the specified coupling strengths can be conveniently satisfied. Finally, a prototype device filter operative at S-band is provided to illustrate the proposed techniques. Salient feature of the size reduction of the novel filter is achieved (more than 70%) when compared to a conventional structure.