Bandwidth-Enhancement Single-Patch Antenna with Dual-Beam Pattern via Seven-Mode Operation

This paper presents a low-profile wideband in-phase-fed microstrip patch antenna (MPA) operating with TM60, TM04, TM62, TM24, TM44, TM82, and TM80 modes. First, a rectangular in-phase-fed MPA is theoretically analyzed to clarify how these seven modes can be effectively utilized for bandwidth enhancement. Then, a transverse slot is incorporated into the patch to progressively move the resonance of the TM04, TM24, and TM44 modes toward that of the TM60 mode. Afterward, a pair of longitudinal slots is further employed to bring the TM62, TM82, and TM80 modes closer to the TM60 mode. In addition, another pair of longitudinal slots is introduced to improve the impedance matching performance. In this way, the seven modes are properly redistributed and grouped within the desired frequency range, thereby enabling broadband operation. Finally, an antenna prototype is manufactured and tested. The experimental results demonstrate that the antenna provides an impedance bandwidth covering 4.4–6.9 GHz while maintaining stable radiation performance, which is about 25 times wider than that of the conventional counterpart. More importantly, the antenna profile is as low as approximately 0.056λ0.