Cavity-Filter-Based 3-D-Printed Gain-Filtering Transmitarray for Multibeam Applications

In this article, a full-metal transmitarray (TA) is proposed with gain-filtering characteristics. The units of the proposed TA are designed based on a square waveguide filter with different orders and cavity widths, but the same passband. The phase variation in the proposed TA is achieved by the large group velocity variation in the evanescent mode in the coupling cavity. Hence, the TA unit can achieve gain filtering and wavefront manipulation simultaneously. To verify the performance of the proposed design, a multibeam TA prototype is designed and fabricated at a center frequency of 26.0 GHz. The size of the TA is $156.0\times 156.0\times116.5$ mm3 ( $13.5\,\,\lambda \times 13.5\,\,\lambda \times 10.1\,\,\lambda$ ). The measured results show that the TA can achieve five beams with the 2-D beam-scanning range of ±28°. It can realize gain-filtering response with the out-of-band suppression levels below −19.0 dB in the main beam directions. In addition, due to the low-loss full-metal waveguide structures, the TA can achieve a maximum aperture efficiency of 45.1%. In our opinion, the high transmission coefficient, passive beam-scanning, and gain-filtering characteristics of the TA make it a good candidate for low-cost millimeter-wave communication and sensing applications.