A Low-Profile Self-Duplexing Antenna for Millimeter-Wave and Microwave Frequency Bands

This paper presents a compact self-duplexing antenna working at mm-wave and microwave frequency bands. The configuration is based on Half-mode Substrate Integrated Waveguide (HMSIW) and operates at 5.8 GHz and 38 GHz. In the design of the antenna, initially, a square cavity is cut into two triangles. Then, one of the triangles is considered. After that, the chosen triangle is bisected into two portions. The bigger one is taken for the microwave frequency band, and the other one is taken for the mm-wave frequency band. Finally, by introducing four capacitive slots, the desired frequency bands are achieved. The isolation between the two ports is 22 dB. In addition, the gains of the proposed antenna at two frequencies are 3.35 dBi (5.8 GHz) and 5.48 dBi (38 GHz). Furthermore, the size of the proposed antenna is only
$0.002 \lambda_{g}^{3}$
which is the most compact self-duplexing antenna in literature that operates at both microwave and mm-wave frequency bands. The aforementioned results show that the proposed antenna is a good candidate to use in dual-band application systems.