High-Gain Filtering Reflectarray Antenna for Millimeter-Wave Applications

This article presents a novel design of filtering reflectarray antenna, an integrated module for the combination of filtering and high-gain radiation performance. The filtering reflectarray consists of two-section metal pixel waveguide elements, which can realize the optimized aperture reflection phase distributions in the operating band $f_{1 similar to \le }f similar to _{\le }similar to f_{2}$ to yield high-gain radiation. Below the lower cutoff frequency $f_{1}$ , the reflection phase distributions drastically deviate from the required ones. Above the upper cutoff frequency $f_{2}$ , both the amplitude and phase distributions fail to provide strong coherent radiation. In the reflectarray synthesis process, a multi-frequency phase matching method (PMM) is further developed, in which the phase compensation for each pixel is implemented at three simultaneous in-band frequencies. Meanwhile, the effects of incident angle for elements are also taken into consideration during the reflectarray synthesis. The design of an $11\lambda \times 11\lambda $ filtering reflectarray operating from 55 to 65 GHz was conveniently fabricated by 3-D printing technology, followed by metal coating with advantages of rapid prototyping, lightweight, and low cost. Both the simulated and measured results show that the proposed reflectarray can realize high-gain radiation within the desired frequency band but presents effective suppression of out-of-band signals, demonstrating its filtering capability.