A novel design to enhance the bandwidth of a low-profile substrate integrated waveguide (SIW) cavity antenna is presented. Distinct from traditional antennas with unilateral slots, bilateral slots are utilized as radiating elements in the proposed design. By etching an additional slot at the bottom plane, a new resonant mode is introduced, and quality factors of two original modes are significantly reduced. Antenna's bandwidth can be dramatically enhanced by merging these three modes within a single operating band. A prototype is fabricated and measured. With the height of 0.018λ0, the measured 10-dB bandwidth is 410 MHz (3.24-3.65 GHz), corresponding to 11.9% fractional bandwidth. The measured gain is higher than 4.3 dBi, and the measured efficiency is around 75% within the operation band. Those attractive features, e.g. low profile, enhanced bandwidth and moderate radiation performance, make the proposed antenna suitable for future 5G systems.
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