Ultracompact Quarter-Mode Substrate Integrated Waveguide Self-Diplexing Antenna

A highly compact substrate integrated waveguide (SIW) self-diplexing antenna, operating at wireless local area network bands (3.6 and 5.4 GHz), is proposed in this letter. The proposed antenna consists of two closely placed (0.022λ
_g
, where λ
_g
is the guided wavelength at 3.6 GHz) quarter-mode SIW resonators, exited by two coaxial probes. Two rectangular slots are added to the closed-ends of each resonator to generate additional capacitances. Therefore, both resonators operate below their fundamental frequencies, and hence, miniaturization is achieved. Moreover, a reliable circuit model is developed to validate the design process. The proposed antenna has ultracompact dimensions of 0.08λ
_g
²
with simulated gains of 4.9 and 5.34 dBi at 3.6 and 5.4 GHz, respectively. In addition, the simulated isolation levels are 32.5 and 36.6 dB at the lower and higher resonant bands, respectively. Furthermore, both resonant frequencies can be independently controlled by changing the length of the capacitive slots. Due to its compactness, independent resonance control and high isolation, the proposed antenna is suitable for compact and planar radio frequency components.