Design of a Closely Spaced-Bands Self-Diplexing Antenna Based on HMSIW Technology

This work presents the design of a novel selfdiplexing antenna featuring high isolation characteristics, implemented using half-mode substrate-integrated waveguide (HMSIW) technology. Dual-band functionality is realized by etching a T-shaped slot on the top metal layer, enabling the HMSIW structure to resonate at two separate frequencies, 3.30 GHz and 3.65 GHz, using non-parallel microstrip feed lines. The electromagnetic response of the structure was thoroughly investigated through high-fidelity simulations conducted in Ansys HFSS. The antenna's performance is analyzed through a lumped circuit model. By precisely tuning the antenna's dimensions, remarkable isolation of over 34 dB between the two input ports is achieved. The proposed radiating structure attains peak realized gains of 2.8 dBi at 3.30 GHz and 5.7 dBi at 3.65 GHz, while sustaining a front-to-back radiation ratio exceeding 16 dB across both spectral bands. The compact design, with a circuital architectural of only <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\left(0.71 \lambda_{g}{ }^{2}\right)$</tex>, meets the growing demand for simplicity and integration in RF devices, offering greater isolation and a smaller footprint compared to previous designs.