Analysis and Design of a Full 360 degrees, Harmonic-Suppressed Hybrid Coupler Phase Shifter

The analysis and design of a full 360 degrees hybrid coupler phase shifter with integrated distributed elements low pass filters is presented. Pi-section filter is incorporated into hybrid coupler phase shifter for harmonic suppression. The physical size of the proposed structure is close to that of the conventional hybrid coupler phase shifter. The maximum phase shift range is bounded by the port impedance ratio of the hybrid coupler phase shifter. Furthermore, the phase shift range is reduced if series inductance in the reflective load deviates from the optimum value. Numerical and parametric analyses are used to find the equivalent circuit of the pi-section filter for consistent relative phase shift. To validate our analysis, the proposed phase shifter operates at 8.6 GHz was fabricated and measured. Over the frequency range of interest, the fabricated phase shifter suppresses second harmonic and achieves analog phase shift of 0 to 360 degrees at the passband, agreeing with the theoretical and simulation results.