Implementation of UWB BPF with modularised design based on SQR and DCR

Abstract

Two ultra-wideband (UWB) bandpass filter (BPF) with fractional bandwidths of 30% (1.2 GHz) and 52% (2.5 GHz) are developed and named as UWB BPFs I and II, respectively. Two novel generation approaches of resonant mode (RM) are first presented and analysed, which are named as synchronous-quasi-resonance (SQR) and double-curved-route (DCR), assisting in generating more RMs with the same prototype. First, an admittance prototype and its equivalent network are proposed to realise an UWB with multi-RMs and transmission zeros (TZs), whose detailed generation mechanisms are discussed. Then, two UWB BPFs are implemented employing the same prototype and design procedures. Their distinct characteristics of frequency response show that the one employing SQR and DCR can generate three more in-band RMs and one more TZ in high rejection band over another, which leads to a 1.3 GHz wider bandwidth and 1.0 GHz more harmonic suppression. Finally, a modularised design model is proposed to build the UWB or multi-band filters requiring arbitrary numbers of RMs and TZs.