Sub-6 GHz High FOM Liquid Crystal Phase Shifter for Phased Array Antenna

Abstract

This paper presents a novel structure based on liquid crystal (LC) technology to achieve a high figure of merit (F OM) phase shifter that works at sub-6 GHz frequencies. The phase-shifting mechanism is enabled through the phase constant variation in the main microstrip line, which is loaded periodically by a variable equivalent capacitance controlled by a bias voltage. Furthermore, a systematic approach based on a transmission line circuit model and the periodic structure theory is developed as a fast method for design optimization by using the ADS and HF SS software. The fabricated phase shifter achieves a maximum insertion loss of 4.35 dB and a maximum phase-shift of 461 • at 4 GHz, which indicates an F OM equal to 105.9 • /dB. Moreover, the phase shifter return loss is better than -10 dB from 3.7 GHz to 4.2 GHz, covering the sub-6 GHz 5 G band. To validate the performance of the proposed phase shifter, a 1-D electronically steered phased array is designed, fabricated and tested by using a 4 ×4 aperture-coupled patch antenna array, excited by a continuous RF phase-shifting mechanism. The patch antenna array, as a 4-port radiation component, is designed with HF SS full simulation, and achieved a fractional bandwidth of 30% at 4 GHz. The phased array prototype exhibits a continuous beam scanning over the elevation range of 0 • to 20 • . According to the achieved F OM, and an integrable structure with the printed circuit board (PCB), the proposed low-cost and low power phase shifter is a good candidate for 5G application.INDEX TERMS Phased array, phase shifter, liquid crystal (LC), patch antenna array, beam steering, beamforming.This article has been accepted for inclusion in a future issue of this journal. Content is final as presented, with the exception of pagination.

Fast Reconfigurable Phase Shifter Based on a Chiral Liquid Crystal Configuration

“…However, since our design is also considered to be applied to a 2-dimensional array, the area of the circuit was very limited. Panahi et al [18] show a very attractive FoM of 105.9 • /dB at 4 GHz, but the space occupied by the phase shifter line is 616 mm 2 , much larger than the 70 mm 2 occupied by our proposed phase shifter. The loss is an essential factor in the phase shifter application, so we will continue to optimize the loss in future work.…”

“…Recently, various research groups have reported the application of LCs to multiple circuits, such as frequencytunable planar antennas, phase shifters of microstrip and co-planar structures, frequency-tunable filters of waveguide structures, and beamforming array antennas [13], [14], [15], [16], [17], [18], [19], [20], [21], [22]. Several types of research have been conducted to reduce the response time of LC-based RF circuits.…”

Reconfigurable holographic leaky‐wave antenna based on liquid crystal materials

“…This design combines the excitation source and radiation structure of the traditional holographic antenna to realize the integration of the antenna. Compared with the traditional phased array antenna, 9,10 the microwave holographic antenna does not need phase shifting units, making the structure more streamlined. Compared with the traditional reflective array antenna, 11,12 the feed form is more flexible, and the shielding of the feed can be avoided, greatly improving the monitoring range of the antenna system.…”