Complex loads for millimeter-wave digital phase shifter design

The design of a reflection-type digital phase shifter comprising complex loads at the coupler´s 3dB output ports is presented. These loads provide the possibility of adjusting both the phase increment and the phase frequency response. The created out of band resonances enable small phase deviation and low loss characteristics. In this contribution, the design concept is analyzed based on a K-band phase shifter featuring a constant phase response. Simulation results show an absolut phase error of less than 3.0° within a relative bandwidth (RBW) of more than 30% and high robustness against fabrication tolerances. Measurement results of a realized 180 ° phase shifter agree well with simulation, and confirm the accuracy of the analysis and the feasibility of the concept.