Synthesis of lumped‐element dual‐band bandpass filters with independently controllable bandwidth

Abstract

In this article, a novel synthesis method for lumped-element dual-band bandpass filters (DBPFs) with independently controllable bandwidth is proposed. The proposed lumped-element DBPF exhibits the advantages including two passbands with independently controllable bandwidth, arbitrary frequency ratio, availability for different lowpass prototypes, and compact size below 6 GHz. This design theory is based on the equivalents of dual-band J-inverters and LC resonators which combines generalized dual-band resonators theory with independently controllable bandwidth. A dual-band bandpass frequency transformation and four circuit conversions are derived. For demonstration, three cases of DBPF with different bandwidths, frequency ratios, and orders are designed, fabricated, and measured. The simulated and measured results have a good agreement, validating the proposed synthesis theory.