Planar UWB phase shifter using parallel coupled lines combined with short-ended stubs and impedance transformer

An ultra-wideband (UWB) phase shifter with wide range of differential phase shift is proposed. To achieve this performance, the design uses quarter wavelength parallel coupled lines combined with short-ended stub structure and an impedance transformer. The value of the differential phase can be adjusted through varying the coupling coefficient of the coupled lines along with the length and impedance of the short-ended stubs and transformer. The theory of operation for the proposed designs is explained. To validate the theory, two phase shifters are designed to realize 90° and 180° differential phase across the band 3.1-10.6 GHz with less than ±11° differential phase imbalance and less than 1.2 dB insertion loss.