Design and Characterization of Beam-steering Phased Array Antenna using Tunable Phase Shifter based on BST varactor

Abstract

Beam steering phased array antenna is a technology that can be used in wireless systems such as tracking and detection radar, and communication applications. In particular, it plays an important role in increasing the transmission efficiency of mobile communication systems. Active beam steering technology provides stable transmission performance by forming an optimal radiation pattern in the desired direction. As for the beam steering method toward the target object, research is being actively conducted for electrical beam steering rather than mechanical beam steering. One of the important components for efficient electrical beam steering is the phase shifter. Since the phase shifter determines the performance of the phased array antenna, the development of a miniaturized high-quality phase shifter is an essential research. In this thesis, we design a tunable phase shifter based on barium-strontium-titanate (BST) varactor and present a beam steering phased array antenna combined with it. The phase shifter is provided with a grounded vias and periodic microstrip meander line equipped with BST varactor to miniaturize the size of components. Since this structure is a simple compact periodic structure, the phase shift can be extended regardless of the effect of parameter variation. Also, based on a conventional right-handed transmission line, a varactor-loaded transmission line equivalent circuit is proposed to achieve more accurate modeling by taking parasitic parameters of practical lumped-element and meander line structure in consideration. The phase shifter achieved a phase shift of 368 ° and a FoM of 68°/dB at 2.5 GHz. The phased array antenna consists of four elements of a rectangular ring-gap coupling patch and employs aperture-coupled feeding technique. The 1x4 phased array antenna steers the beam from -40° to +40° while maintaining a constant beam width and provides a peak gain of 9 dBi. Through this work, we have achieved continuous beam steering with maximum beam tilt angle, which can be used in applications for efficient wireless communication.