A High-gain Tri-band Shared-aperture Antenna for Microwave and Millimeter-wave Applications

In this paper, a microwave (MW) / millimeter-wave (MMW) tri-band shared-aperture antenna is proposed. This antenna operates as a $2 \times 2$ monopole array at 3.5 GHz and as a transmitarray (TA) antenna at 26 GHz and 39 GHz, respectively. In particular, the TA is a frequency selective surface (FSS) type, which consists of four layer substrates and the bottom layer is reused as the monopole array. In the unit cells of the TA, two kinds of rectangular slots are designed to control the phase shifts in 26 GHz and 39 GHz bands independently. The results show that the antenna achieves a peak gain of 12.5 dBi in the MW band and demonstrates a gain of 14.7 dBi at 26 GHz and a gain of 18.2 dBi at 39 GHz, respectively.