Abstract

Compact planar phase shifters with wide range of differential phase shift across ultra-wideband frequency are proposed. To achieve that performance, the devices use broadside coupled structure terminated with open-ended or short-ended stubs. The theory of operation for the proposed devices is derived. To validate the theory, several phase shifters are designed to achieve a differential phase ranging from -180° to 180°. Moreover, three prototypes are developed and tested. The simulated and measured results agree well with the theory and show less than 7° phase deviation and 1.4 dB insertion loss across the band 3.1-10.6 GHz.

Introduction

PHASE shifters are widely used in many microwave systems, such as phased arrays, modulators, microwave instrumentation and measurement systems. Different techniques are used to build planar phase shifters with wideband performance, such as broadside-coupled structure [1]–[۴], modified Schiffman [5], composite right/left-handed transmission lines [6], loaded transmission lines [7], substrate integrated waveguide [8]–[۱۰], double microstrip-slot transitions [11], or metamaterials [12]. A careful inspection of the performance of the developed phase shifters indicates that only a few of them cover the ultrawideband (UWB) frequency range (3.1–۱۰٫۶ GHz) [1]–[۴], [۷], [۱۱]. Despite their excellent performances across almost the whole UWB range, one section of those devices can achieve a maximum phase shifts of 45 [1]–[۳], or 90 [4], [7], [11]. Thus, to achieve wider phase ranges, multiple sections of those devices are to be cascaded. That approach causes an increase in the phase deviation, insertion loss, and size.