Bandwidth-Enhanced Miniaturized Patch Antenna Operating at Higher Order Dual-Mode Resonance Using Modal Analysis

This letter presents a novel technique for miniaturization and bandwidth enhancement of a rectangular microstrip antenna (RMA) operating at a higher order TM03-like mode. The resonant length of a conventional RMA supporting the TM03 mode is reduced by λ/4 (λ is the operating substrate wavelength) by this design at the operating frequency. Consequently, the conventional resonant length of 1.5λ for this mode is reduced to 1.25λ. Excitation of this TM03-like mode increases gain as well as the antenna efficiency at the design frequency of 5.8 GHz. A wide slot is placed on the patch to reduce the sidelobes of the radiation pattern. Three meandered line linkages are placed inside the slot to miniaturize the structure maintaining current continuity. Resonance behavior of the antenna is studied using theory of characteristic modes and the impedance bandwidth is enhanced by controlling the excitation of the next higher order mode in the vicinity of TM03-like mode by appropriately choosing dimensions of the meander lines. The antenna is fed by a coaxial probe and is easy to fabricate. Measurement shows an impedance bandwidth of 8.5% and a peak gain of 10.5 dBi. The overall size of the designed antenna is 1.31λ0 × 1.31λ0 × 0.03λ0 (λ0 is free-space wavelength at 5.8 GHz).