Switchless Multi-Octave Tune-All BPF Manifold Using Low-Pass/High-Pass Diplexer Junctions

This paper presents an RF-switchless two-bandpass filter (BPF) manifold with continuous multi-octave center frequency (f_cen) and bandwidth (BW) tuning capabilities that are demonstrated in a wide range of frequency range 1 (FR1) bands, spanning from L-band to C-band. Specifically, the proposed RF filtering component operates in three distinct modes of operation, namely: i) single-band, ii) dual-band, and iii) all-reject - achieved by intrinsically switching ON/OFF its two BPF branches. It is based on two tune-all BPFs that are combined with two high-pass/low-pass RF diplexer-based filtering junctions. A technique to minimize insertion loss (IL) using varactors and high-Q static DC block capacitors is demonstrated. The experimental prototype exhibits: i) a single-band mode of operation with f_cen tuning between 1.89-7.28 GHz, BW tuning ratio of 3-4.4:1 and minimum in-band insertion loss (IL): 2.3-5.7 dB), ii) a dual-band mode of operation with two independently tuned bands, and iii) an all-reject mode of operation with isolation < 15 dB between DC and 18 GHz.