Parametrically Enhanced Bandpass Filters

This paper proposes a technique to enhance the quality factor (Q) of a resonator, which can then be used to realise bandpass filters (BPFs) with reduced insertion loss (IL) and improved passband selectivity. The main idea behind this technique is to introduce a negative resistance to a resonator, through the parametric amplification effect, to compensate losses from non-ideal passive components (e.g. capacitors, inductors, and microstrips). Two bandpass filters enhanced by such resonators are designed and realised on printed-circuit boards (PCBs) to demonstrate the characteristics of low insertion loss and good passband selectivity. In addition, these prototype parametrically enhanced filters offer reasonably good linearity and similar noise figures (NFs) to their corresponding pure passive counterparts.