A Wideband Beam-Scanning Reflectarray Based on the 1-bit Tightly Coupled Unit Cell

In this article, a wideband beam-scanning reflectarray antenna is proposed. The reflecting surface is built based on the 1-bit tightly coupled elements. The phase control is achieved by loading radio frequency (RF) switches on the delay lines of the elements. To obtain better sidelobe levels (SLLs) and beam directions, the state of the RF switch on the reflecting surface is optimized by applying particle swarm optimization (PSO). Additionally, a novel method for calculating the reflection phase of the strongly coupled elements is proposed. To verify the design, a prototype reflectarray consisting of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$27\times 9$ </tex-math></inline-formula> elements is simulated, fabricated, and measured. Measured results show that the proposed reflectarray can achieve ±45° beam scanning from 4 to 6 GHz with the stable main beam.