A Reflection‐Type Dual‐Band Phase Shifter with an Independently Tunable Phase

This paper presents a design for a dual‐band tunable phase shifter (PS) with independently controllable phase shifting between each operating frequency band. The proposed PS consists of a 3‐dB hybrid coupler, in which the coupled and through ports terminate with the same two reflection loads. Each reflection load consists of a series of quarter‐wavelength (λ/4) transmission lines, λ/4 shunt open stubs, and compensation elements at each operating frequency arm. In this design, a wide phase shifting range (PSR) is achievable at each operating frequency band (fL: lower frequency; fH: higher frequency) by compensating for the susceptance occurring at the co-operating frequency band caused by the λ/4 shunt open stub. The load of fL does not affect the load of fH and vice versa. The dual‐band tunable PS was fabricated at fL = 1.88 GHz and fH = 2.44 GHz, and testing revealed that achieved a PSR of 114.1° with an in‐band phase deviation (PD) of ± 8.43° at fL and a PSR of 114.0° ± 5.409° at fH over a 100 MHz bandwidth. In addition, the maximum insertion losses were smaller than 1.86 dB and 1.89 dB, while return losses were higher than 17.2 dB and 16.7 dB within each respective operating band.