CMA Approach for a DGS-Based Wideband Circular Patch Antenna With Low Cross Polarization
Deepak Kumar Naik, Rajanikanta Swain, Dhruba C. Panda, Rabindra Kishore Mishra
Abstract
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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\simeq$</tex-math></inline-formula> 16% impedance bandwidth (5.7–6.7 GHz) with dimensions <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{0.8\lambda _{0}\times 0.8\lambda _{0}\times 0.03\lambda _{0}}$</tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{\lambda}_{\boldsymbol{0}}$</tex-math></inline-formula> being the free-space wavelength at 6 GHz) and 10–15 dB average cross polarization reduction at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula> 60° angle of boresight. The measured results from a fabricated prototype agree well with the proposed design.