Filtering Phase Shifters Using Vertically Installed Planar Structure

In this paper, a wideband filtering phase shifter (PS) is proposed using vertically installed circuit structures, where the VIP circuit is used to realize a tight coupling. The even-odd mode analysis is adopted to analyze the whole structure. Then, a 45° filtering PS is designed to verify the design methodology. The simulated and measured results demonstrate that the proposed phase shifter has low insertion losses (<0.5 dB) and excellent return losses (< -15 dB). The 3°-phase shift bandwidth is more than 64.31%.

I. Introduction

Phase shifters (PS) are widely used in various integrated circuits and systems, such as beamforming networks and phased-array antennas. Schiffman phase shifter and its modified structures are more popular for their simple topologies [1], while due to the limitation of manufacturing technology, it's hard to obtain extremely tight coupling. Recently, filtering phase shifters have been extensively investigated due to their good in-band and out-band performances, and a variety of methods have been applied to improve the bandpass character-istics of phase shifters so far. Of them, the stub loaded [2] and multimode resonators [3] are proposed to extend the 3 -dB bandwidth of the phase shifter. However, transmission lines are employed as the reference line in [1]–[3], which suffer from the limitation of phase shift bandwidth. Meanwhile, cou-pled T-shaped resonator [4], [5] or open/short stubs [6] can also make phase shifters obtain filtering response, despite the unexpected large circuit sizes. Besides, transmission lines with π-shaped stubs [7] and three-coupled lines with three mi-crostrip lines [8] are proposed to develop dual-band phase shifters with compact size, which also introduce the complexi-ty in both of the topologies and synthesis design procedures.