A Low-Loss Broadband Tunable Phase Shifter Based on Transversal Signal-Interference Circuit

This letter presents a broadband tunable phase shifter (PS) based on a transversal signal-interference (TSI) structure. The proposed design incorporates three varactor diodes as the tunable components. All of these varactors are controlled by a unified dc voltage and are terminated on a coupled line and a shunt stub. The combination of the coupled line and stub-loaded line enables the proposed PS to achieve a wider bandwidth. The measurement results indicate that the prototype PS achieves a 10-dB return loss (RL) bandwidth of 2.0–2.8 GHz (fractional bandwidth (FBW) =33.3%), a maximum relative phase shift of 110°, an average insertion loss (IL) of 0.89 dB at center frequency, and a size of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.053\lambda _{g}^{2}$</tex-math> </inline-formula>.