Broadband Integrated Differentially Fed Patch Antenna With Tightly Coupled Elements

This letter presents the design and test results of a broadband patch antenna integrated on a three-layer substrate, working at 7.3–9.8 GHz. Based on U-shaped slots and tight coupling, the broadband characteristic is achieved. The antenna model is 20 mm (
${\text{0.568}}\lambda _{0}$
) long, 20 mm (
${\text{0.568}}\lambda _{0}$
) wide, and only 1.8 mm (
${\text{0.052}}\lambda _{0}$
) high, with an extremely low profile for integration. Finally, the patch antenna is fabricated and measured. Experimental results show that the proposed antenna possesses a 10 dB
$|S_{11}|$
bandwidth of 33.9% and 3 dB gain bandwidth of 36.3%.