Broadband Electronically Scanned Reflectarray Antenna With Liquid Crystals

In this letter, an electronically beam scanning reflectarray antenna is implemented using nematic liquid crystals (LCs). By loading a tunable phase shifter with a delay line structure in the resonance unit, the phase shift is achieved by tuning the dielectric constant of the LCs with a fixed structure through an external dc bias voltage for each unit. In doing so, dynamically controlling the reflection phase of each independent unit is realized. The experimental results show that the plane reflectarray unit can obtain a phase shift exceeding 360° with good linearity, and the maximum reflection loss is 7 dB. Moreover, a 10×10 LC-based planar reflectarray is fabricated and measured, and the bias voltage is loaded by a 100 outputs field-programmable gate array voltage module. In the frequency range of 22.1-26.1 GHz, its 3 dB relative bandwidth is 16.7%, the maximum gain of the main lobe is 20.2 dBi, and the maximum scanning angle is ±45°. The results verify the 2-D scanning functionality and the feasibility of improving the bandwidth of planar reflectarray antenna using LCs.