Continuously Tunable Inductorless Phase Shifter Unit Cell Based on NRI-TL Metamaterial

A simple method for the design of a continuously tunable phase shifter based on a negative-refractive-index transmission line (NRI-TL) metamaterial without the need for variable inductors is presented. The employed λ/4 transformer solution consists of only three varactor diodes and three corresponding bias resistors, which greatly simplify the design and lower the cost of the phase-shifting stage. A single unit cell of the phase shifter prototype exhibits a total phase shift of 60° over 4V at 2.4GHz and a fractional bandwidth of 37% with insertion loss of only 0.5dB. Some of the drawbacks are also discussed.