Ultracompact Quarter-Mode SIW Self-Hexaplexing Antenna for C-Band and X-Band Applications

In this letter, an ultracompact substrate integrated waveguide (SIW)-based hexaplexing antenna, operating at six distinct frequencies (4, 5.8, 6.6, 7.8, 9.8, 10.68 GHz) is proposed. It is made up of four compacted square-like quarter-mode SIW (S-QMSIW) resonators, and two triangular (T-QMSIW) elements. Their compactness is accomplished through the inclusion of rectangular slots at the closed-off ends of each resonator, resulting in increased shunt capacitance. As such, the resonance frequencies shift to the lower spectrum of their fundamental frequency ranges, forming the full hexaband system, with only 0.14
$\lambda _{g}^{2}$
in size. In addition, the minimum attained isolation level is 27 dB. At the intended frequencies, the maximum realized gain and efficiency are 4.9, 5.11, 5.4, 5.43, 5.32, and 5.3 dBi, for gain; 94%, 94.3%, 95%, 96.5%, 94%, and 95.7% for efficiency, at 4, 5.8, 6.6, 7.8, 9.8, and 10.68 GHz, respectively. In addition, a reliable equivalent circuit model is designed to confirm the proposed methodology, and the final design is fabricated. The simulation results are in good agreement with the measured ones. The proposed design proved its flexibility in terms of independent frequency tuning, thus making it an appealing choice for ultracompact communication systems.