Wide frequency range four-bit reconfigurable resonator employing λ/2 and λ/4 resonant modes

In recent years, RF circuits that can flexibly select many RF frequency bands have been pursued. A two-stage reconfigurable band-pass filter (BPF) with three-bit/eight-frequency selection capability has been proposed for this goal. However, it employs λ/4 resonant mode only, resulting in a limited frequency variable range. This paper proposes a new four-bit reconfigurable resonator employing λ/2 and U4 resonant modes to cover a wider frequency range and more number of selectable frequencies. A prototype using high dielectric printed circuit board has been fabricated and evaluated. The measurement results validate that the sixteen frequencies can be switched in 1.5-3.6 GHz with low insertion loss of less than 1.8 dB.