Low‐profile SIW cavity antenna with enhanced bandwidth and controllable radiation null

Abstract

A low‐profile substrate‐integrated‐waveguide (SIW) cavity antenna with enhanced bandwidth and a controllable radiation null is proposed. Serving as radiating elements, two slots are etched on a square SIW cavity. Four cavity modes including a fundamental mode (FM), a half mode (HM), and two quarter modes (QMs) are excited by a capacitively coupled feeding disc. Their frequencies can be controlled by adjusting positions of the slots and disc. Three radiating modes (ie, a HM and two QMs) are utilized to realize an antenna passband with enhanced bandwidth while a nonradiating mode (ie, the FM) is utilized to achieve a radiation null resulting in the sharp upper sideband and high stopband suppression. Experimental results show that the fabricated antenna with the profile of less than 0.04λ0 obtains the bandwidth of 440 MHz, gain of 5.24 dBi, and efficiency of 84%. However, the gain sharply drops to −22.07 dBi and the efficiency achieves a very low value of 0.15% at the radiation null. Due to covering the frequency band of 3.40‐3.60 GHz, the proposed design has potential applications for fifth‐generation (5G) wireless systems.

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