Proposal and Design of Filtering 0°/180° Phase Shifter for Modern Wireless Communications

In this paper, a fixed response 3.5-GHz filter-integrated SPDT switch with ripple bandwidth (RBW) of 195 MHz is designed using capacitively coupled LC resonators. The switch consists of five capacitively coupled LC resonators and four groups of P-I-N diodes, and three ports all use a 50 feeder circuit. The ports’ opening and closing are controlled by controlling the forward or reverse bias of the diodes. However, p-i-n diodes have a certain influence on the state channel. Then, four sets of P-I-N diodes are replaced with their equivalent circuit in the design. Based on this, a new design scheme of 0°/180° filter phase shifter for modern wireless communication is proposed. The working state of the phase shifter is changed by changing the diode state. The electric length of the transmission line used in this design can effectively avoid series resonance. At the same time, the transmission lines in this design are far away from each other to prevent coupling. Moreover, the filter function of the phase shifter allows it to filter out other rf signals effectively and realize a more accurate phase shift of useful RF signals. Simulation results show that the design has a better reflection coefficient and higher isolation degree, and has a relatively small circuit size. The design simulation and physical test results will be presented and analyzed at the end of the article.