A novel 360° continuously tunable phase shifter based on varactor-loaded CRLH transmission line at exact 2.4 GHz

In this work, a novel phase shifter using five unit cells of the varactor-loaded composite right/left-handed (CRLH) transmission line (TL) is presented, achieving a continuously tunable phase-shift of approximate 360° at the exact 2.4 GHz. The CRLH-TL unit cell includes 3 electrically tunable varators (two series ones and a shunt one) which allow phase shift change at 2.4 GHz, and a biasing network is introduced, which allows the unit cells to be controlled by a single voltage. The capacitance of all the varactors can be controlled at the same time, and the full 360° range of phase shift can be achieved. To prove the concept, the final layout of the phase shifter can be fulfilled. Measured results demonstrate a tunable phase shift of 360° at the operation frequency of 2.4 GHz when bias voltage varies from 0 V to 4 V, along with an optimal impedance matching. A miniature size of 9 mm, which is 1/8 λg, is optimized for each cell to ensure a compact size for the final layout of the phase shifter. Excellent performance such as return loss greater than 14.5 dB, and insertion loss blow 2.5 dB is also indicated in our work. Good agreement between simulation and measurement is observed to certify the validity of the proposed work.