Investigation on Asymmetric Parallel-coupled CPW for λ/4 Bandpass Filters with Broad Rejection Band

Abstract

Asymmetric parallel-coupled coplanar waveguide (CPW) is originally characterized here as an equivalent unified K-inverter network. On a basis of our developed self-calibrated method of moments (MoM), the relevant network parameters are extracted to explicitly demonstrate the frequency-dependent coupling behavior with the 1st zero coupling at the λ/2 length of overlapped section. By differentiating the coupled spaces and overlapped lengths, the two CPW coupling structures are dissimilarly constructed and utilized as the input/output excitation of a λ/4 CPW bandpass filter. Through allocating the two unequal zeros towards the spurious harmonic around 3λ/4, an improved two-stage λ/4 CPW filter is designed at 5.0GHz. Optimized results achieve broad rejection band, ranging from 5.8GHz beyond 18.0GHz, as verified by the ADS simulation. © 2004, The Institute of Electronics, Information and Communication Engineers. All rights reserved.