Miniaturized Self‐Diplexing Antenna Design With Dual‐Mode Operation in Each Band and Based on a Double‐Layered Open Cavity

This paper presents a miniaturized self‐diplexing antenna with dual‐mode operation in each band. The design is based on a single open cavity of the substrate integrated waveguide type, which contains double substrate layers and double patches. The cavity may generate modes in pairs with four magnetic side walls, similar field patterns in the horizontal substrate plane, and near resonant frequencies. By selecting the lowest order paired TE 100 and TEM 001 modes as working modes, not only double‐resonance points in each frequency band but also significant miniaturization can be achieved. It offers excellent independent frequency tuning compared with stacked microstrip patch antennas. The antenna has a very compact size of 0.48 × 0.41 × 0.03 λ 3 , where λ is the dielectric wavelength at the center frequency of the lower band. To validate the proposed design, a prototype of the antenna is fabricated and tested. The measured bandwidths are 3.04% and 3.12%, and realized gains 6.27 and 6.56 dBi for the lower and higher bands, respectively. The measured isolation between the two input ports is less than −30 and −28 dB for the two bands, respectively. The designed antenna demonstrates excellent performance, with a simple design process supported by fundamental analysis.