Wideband Filtering Phase Shifter Using Transversal Signal-Interference Techniques

A wideband filtering phase shifter is presented in this letter using transversal signal-interference techniques. The proposed structure creates two signal-propagation paths by introducing extra coupling between two short-ended stubs. Cascaded coupled-line sections and parallel short-ended stubs can generate a constant passband and multiple transmission zeros (TZs) in the stopband and meanwhile provide the arbitrary value of phase shift within the filtering band range. The positions of TZs and phase shift range can be easily controlled. Explicit relations between the objective filtering band and the related parameters are given, and cases with different in-band phase shift values are studied. To validate the design, a prototype is built, simulated, and tested using microstrip lines. The experimental results agree with the predicted ones, demonstrating that the device can realize any given in-band phase shift with a wideband filtering response.

I. Introduction

Phase shifters are commonly used components in various microwave circuits or systems, such as modulators, beamforming networks, or phased arrays. To obtain high data capacity of wireless channels, wide operating bandwidth is required, and thus wideband devices are highly demanded. Wideband phase shifter has been investigated by using a multilayer broadside-coupled structure [1] or single-layer microstrip structures [2]. Stub-loaded structures were widely used in designing wideband phase shifters, including loaded transmission line [3], radial stub [4], stepped-impedance open stub [5], and short and open-ended stubs [6].