Design of a UWB phase shifter using shunt λ/4 stubs

Abstract

In this paper a novel phase shifter covering the whole UWB frequency range with small phase error is presented. The proposed topology employs a single layer substrate and is easy to fabricate. The phase shifter uses shunt quarter wavelength stubs in the resonator branches and transmission lines (TLs) in the reference branches to achieve phase shifts ranging from 20° to 70° while keeping the return loss above 10 dB. The shunt stubs are used to control the phase response. An additional half wavelength TL is inserted in the large phase shifts to improve the return loss. As examples 22.5° and 45° phase bits are designed and fabricated. Theoretical phase errors of ±2° and ±3° are obtained for the 22.5° and 45° phase bits respectively. The measured phase shifts of the two phase bits are 23.6°±2.7°and 45.8°±4.5° with return losses better than 11 dB and 13.4 dB from 3.1 GHz to 10.6 GHz respectively. The measured amplitude imbalances are less than 0.3 dB. © 2009 IEEE.