Highly Miniaturized Eighth-Mode Substrate-Integrated Waveguide Self-Quadruplexing Antenna

In this letter, an eighth-mode substrate-integrated waveguide (EMSIW) self-quadruplexing antenna is proposed for C-band wireless communication systems. It operates at 4.35, 5.35, 5.90, and 6.75 GHz, where each frequency band can be independently controlled. The full-mode substrate integrated waveguide resonator is symmetrically divided to obtain EMSIW resonators to achieve sufficient compactness. Then, capacitive slots are used to further reduce the size of each resonator. Consequently, the proposed antenna occupies overall area of 0.16
$\lambda _{g}^{2}$
(where
$\lambda _{g}$
is the guided wavelength at 4.35 GHz). Compared with conventional EMSIW resonators, a compactness of 32.2% is achieved using capacitive slots. Moreover, proper gaps between the resonators are maintained to keep the isolation level above 27.3 dB. The peak realized gains are noted to be 4.04, 4.48, 4.55, and 6.12 dBi at 4.35, 5.35, 5.90, and 6.75 GHz, respectively. With these features, the proposed quadruplexing antenna is suitable for next-generation C-band communications due to its compact dimensions, high isolation, independently controllable bands, and high gains.