SIW-based cavity-backed self-diplexing antenna with plus-shaped slot

A substrate integrated waveguide (SIW)-based planar cavity-backed self-diplexing antenna, designed for X-band applications, is presented in this article. The proposed antenna is fed by two orthogonal 50 microstrip lines. Two orthogonal rectangular slots, combination of which makes a plus-shaped slot, of different lengths are etched on the top of the SIW cavity. Due to the unequal arm lengths of the plus-shaped slot, the antenna radiates at two distinct frequencies. An isolation of better than 20 dB is achieved between the two ports and hence, the proposed antenna exhibits self-diplexing characteristics. The antenna offers a gain of 5.7 dBi and 5.94 dBi at 8.55 GHz and 9.77 GHz, respectively.