Dual-Frequency Phase Shifter Design with Large Frequency Ratio

This paper presents a structure and design method of a dual-frequency phase shifter (DFPS) with large frequency ratio. The DFPS is a reflection-type phase shifter that utilizes four symmetrical stepped-impedance transformers to realize a dual-frequency 3 dB hybrid coupler. Two dual-frequency susceptance blocks (DFSBs) realized by stubs are loaded onto two ports of the hybrid coupler to achieve the required phase shifts at the two frequencies. The phase shifts can be independently controlled by setting the susceptances of the DFSBs. A 90° DFPS with frequencies f
1
=0.9 GHz and f
2
=4.68 GHz is designed, fabricated and measured to validate the design theory, and good agreement between the simulated and measured results is obtained. Different simulated phase shifts are achieved by varying the parameters of the loaded stubs.