A Visualized Design Method for 360° Wideband Continuously Tunable Phase Shifters With Low Phase Error and Simple Control Scheme

This article introduces a new design method for 360° continuously tunable phase shifters (PSs) with wide bandwidth (BW) and low phase error. In this design, the concept of the phase slope circle, combined with a geometric method, is proposed to address the key issue of large phase error in reflective-type PS (RTPS). This method can directly evaluate the phase shift range (PSR) and phase deviation of the continuously tunable PS with respect to the varactor capacitance ${C} _{\text {v}}$ . When its trajectory falls on the equal-phase-slope circle, low phase error can be achieved and vice versa. It offers explicit guidance and well-defined design criteria for realizing wideband RTPSs with large PSR and low phase error. We systematically analyze the existing reflective loads, including the capacitive, single resonated, and multiple resonated loads, and explicitly illustrate their limitations. To attain a large PSR and low phase error, new reflective loads consisting of mixed lumped and distributed resonators are proposed, and the underlying working mechanism of low phase error characteristic has been elucidated. We also put forward a quantitative and efficient design method accompanied by formulas. To verify the design concept, two prototypes of the proposed 180° and 360° wideband continuously tunable PSs were designed, fabricated, and measured. Both the simulation and measured results are in good agreement. To the best of our knowledge, as of now, this is the widest 360° continuously tunable PS featuring low phase error and the simplest control scheme in low-cost printed circuit board (PCB) technology. Merely two dc control lines are required to achieve an uninterrupted phase shift adjustment spanning from 0° to 360° across a wide operating BW of 50%. It also has the advantages of compact size, good impedance matching, and low insertion loss (IL).