CMA Approach for a DGS-Based Wideband Circular Patch Antenna With Low Cross Polarization

This letter presents a design approach for a defected ground structure (DGS)-based wideband circular microstrip patch antenna using the characteristic mode analysis (CMA). It emphasizes improving two design aspects: 1) cross polarization reduction and 2) bandwidth enhancement. The CMA unveils the intrinsic characteristic modes in the patch and ground plane, and then, undesired modes are suppressed using a DGS, reducing cross-polarized radiations. Another defect, strategically incorporated into the same DGS, enhances a higher-order nonradiating mode to radiate and increases bandwidth. The proposed design fabricated on an FR-4 substrate achieves a
$\simeq$
16% impedance bandwidth (5.7–6.7 GHz) with dimensions
$\boldsymbol{0.8\lambda _{0}\times 0.8\lambda _{0}\times 0.03\lambda _{0}}$
(
$\boldsymbol{\lambda}_{\boldsymbol{0}}$
being the free-space wavelength at 6 GHz) and 10–15 dB average cross polarization reduction at
$\pm$
60° angle of boresight. The measured results from a fabricated prototype agree well with the proposed design.