Ultra-wideband (UWB) bandpass filter composed of asymmetric E-shaped electrodes for improved out-of-passband

Abstract

IntroductionSince the Federal Communication Commissions (FCC) adopted a First Report and Order in 2002 [1], the research of ultra-wideband (UWB) devices has been greatly accelerated in the microwave and millimeter-wave society, and high performance and compact UWB filters have been proposed. Based on a concept of a multiple-mode resonator, novel filters with an excellent passband and well-suppressed out-of-passband responses have been realized [2-4]. As another approach, a compact planar UWB bandpass filter with deep transmission zeros and a mild in-band group delay, was realized by using tightly coupled E-shaped electrodes [5], and useful design guidelines were reported [6]. Furthermore, a chip-loaded planar UWB bandpass filter was proposed in order to relax fabrication difficulties of developing extremely small gap between the electrodes (8μm, for instance) [7], which idea is useful when supercompact planar UWB filters are designed using the higher permittivity substrate. In this paper, a UWB bandpass filter composed of asymmetric E-shaped electrodes is proposed so as to improve insufficient out-of-passband responses. The basic behaviour of the filter is studied by FEM-based simulations and the results are verified by experiments.