Cascaded Coupled Line Filter With Reconfigurable Bandwidths Using LCP Multilayer Circuit Technology

This paper presents a new design method for reconfigurable coupled line filters. The main aim is to develop an analytical design procedure for designing this type of reconfigurable filter with any orders and bandwidths. The new design procedure allows not only making the design easy, but also increasing the passband performance by eliminating the impedance transformers needed for matching purposes used in previous filters. A reconfigurable bandpass filter of this type is designed that can switch between three distinct bandwidth states ranging from around 26% to 50% ripple fractional bandwidth (FBW) centered at 2 GHz. In addition, liquid crystal polymer (LCP) multilayer circuit technology, which offers a great flexibility in realizing required even- and odd-mode impedances for a wideband coupled line filter, is deployed to implement the designed filter. The reconfigurable filter exhibits insertion losses ranging from 0.57 dB for the widest passband state to 1.95 dB for the narrowest passband state. The fabricated filter shows good agreement with EM simulated results.