Highly Miniaturized Self-Quadruplexing Antenna Based on Substrate-Integrated Rectangular Cavity

This letter introduces a novel self-quadruplexing antenna (SQA) architecture using a substrate-integrated rectangular cavity (SIRC) for compact size, wide-frequency redesignability, and high isolation responses. The proposed SQA is developed by engraving two U-shaped slots (USSs) on the top conductor of the SIRC. The USSs are excited by employing four microstrip feedlines to achieve SQA characteristics. The operating frequencies can be tuned independently according to the assumed targets, with a wide tuning range from 2.3 to 7 GHz. The dimensions of USSs are meticulously chosen to achieve high isolation and compact size. An equivalent circuit is suggested to validate the proposed SQA. Finally, the SQA operating at 2.33, 2.96, 5.43, and 6.15 GHz is fabricated and validated. As compared to the earlier SQAs, the proposed antenna offers competitive performance with a compact size of 0.124λ
²
(45.6% smaller than the most compact SQA reported in the literature), high isolation of 32.5 dB, and a wide tunable range from 2.3 to 7 GHz. Its measured gain is 4.31, 3.39, 6.12, and 4.34dBi at 2.33, 2.96, 5.43, and 6.15 GHz, respectively.