UWB Bandpass Filters with Multi Notched Bands

Abstract

This paper presented ultra-wideband (UWB) bandpass filters with single or multi notched band(s) for the purpose of DAA: Detect and Avoid, to avoid the interference between the UWB radio system and the existing radio system. The filter is based on a novel UWB bandpass filter which consists a broadside-coupled microstrip-coplanar waveguide structure and exhibited its excellent ultra-wideband property, proposed by authors recently. The single and multi notched bands operation was implemented by integrating stub(s) in the broadside-coupled conductors. The resonance of each stub introduces a narrow rejection band in the UWB passband which then results in a single or multi notched band(s). Such UWB bandpass filter with notched band is useful and required in practical systems in order to avoid the interference between the UWB radio system and existing radio systems. The notched band can be easily designed to some specific frequency band(s) by tuning the length of the stub(s). Simulation, design, fabrication and measurement of the UWB bandpass filters with notched bands have been carried out mainly following FCC's spectrum mask. The proposed filters demonstrated both excellent ultra-wide bandwidth (from 2.8 GHz to 10.2 GHz) and rejection performance (> 50 dB at central frequencies for a single notched band, or 21 dB and 27 dB for triple bands), as well as good out-band performance better than the requirement of FCC's mask.