Double Microstrip-Slot Transitions for Broadband ${\pm} 90^{\circ}$ Microstrip Phase Shifters

The letter describes double microstrip-slot transitions for use in planar ± 90° phase shifters. The described devices exhibit broadband performance and offer compatibility with ordinary microstrip circuits. Full-wave EM simulation results show a phase shift of ± 90° ± 7° over the frequency band of 3.1-12.0 GHz when compared with a suitably chosen section of microstripline. The observed differential phase shift is accompanied by return losses of not less than 14 dB and insertion losses between 0.7 to 1.5 dB in the band 3.1-11.0 GHz. The simulated performance is confirmed by experimental results of ± 90° ± 8° phase shift, return loss not less than 14 dB and insertion loss between 0.5 and 1.8 dB in the frequency band of 3.1-11.0 GHz.