Bandpass Filters with Ultra‐Wideband Reflectionless Characteristic for Both Two Ports

ABSTRACT In this paper, a class of bandpass filters (BPFs) with symmetric ultra‐wideband reflectionless characteristics is presented. Specifically, two types of reflectionless BPFs are proposed by integrating multiple bandstop sections with embedded absorption resistors. To further enhance port reflection suppression, two distinct methods of introducing additional reflection zeros (RZs) are implemented. To practical verification, prototype circuits of five‐stage reflectionless BPFs with a center frequency of 2 GHz were designed, simulated, and fabricated. Measurement results demonstrate that the two BPF prototypes achieve fractional bandwidths of 32.9% and 29.0%, respectively, with over 10 dB reflection suppression across frequency ranges of 0–5.59 f 0 and 0–5.62 f 0 . The experimental results validate the effectiveness of the proposed approach in achieving ultra‐wideband reflectionless performance.