Compact ultra-wideband 90° phase shifter using short-circuited stub and weak coupled line

A compact ultra-wideband 90° phase shifter based on a short-circuited stub and a weak coupled line (WCL) is proposed. The circuit configuration and derivation of S-parameters and phase difference are presented. The analysis result indicates that the phase deviation (PD) bandwidth can be extended to 200% by adjusting the coupling coefficient of the WCL. The fabricated phase shifter exhibits a bandwidth of 118% from 0.66 to 2.56 GHz for return loss >10 dB, insertion loss (IL) <;0.5 dB and a PD of ±3.9°. Comparison shows that the proposed phase shifter not only has the most compact size with single-layer structures but also achieves the largest bandwidth and lowest IL. The design features low-cost, good design portability and convenient installation. Thus it is a good candidate for wideband and ultra-wideband applications.