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 <tex-math notation="LaTeX"></tex-math> 16% impedance bandwidth (5.7–6.7 GHz) with dimensions <tex-math notation="LaTeX">0.8λ ₀× 0.8λ ₀× 0.03λ ₀</tex-math> ( <tex-math notation="LaTeX">λ₀</tex-math> being the free-space wavelength at 6 GHz) and 10–15 dB average cross polarization reduction at <tex-math notation="LaTeX">±</tex-math> 60° angle of boresight. The measured results from a fabricated prototype agree well with the proposed design.