Synthesis design of equal‐length phase shifter based on substrate integrated waveguide and microstrip line

Abstract

In this article, a synthesis design approach for equal-length phase shifter based on substrate integrated waveguide (SIW) and microstrip (MS) line is presented. It is a novel and effective design method of equal-length phase shifter. The propagation constants in SIW(TE10) and MS(Quasi-TEM) are nonlinear and approximately linear, respectively. Therefore, the equal-length phase shift for SIW and MS, is not a constant, but changes with its frequency. In this work, the propagation constant with nonlinear curve in SIW can be tuned to a straight line in a single band range, originated from mathematical fitting. Based on the linearized operating mechanism of linearization curve for phase shift presented in SIW, the equal-length phase shifters are implemented on the combinational circuit of empty substrate integrated waveguide and MS line firstly, where only one tuning parameter is needed to control the phase shift. Two prototypes are designed, fabricated and measured in Ka-band for validation. Measurement results show that its return losses, insertion losses, amplitude imbalance and phase shifts are 15.2 dB, 1.59 dB, 0.13 ± 0.37 dB, 44.8° ± 2°, and 89.3° ± 4.2°, respectively.