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Broadband circularly polarized patch antenna with low crosspolarization using artificial ground structure
Author(s) -
Kai Yujiro,
Fukusako Takeshi
Publication year - 2018
Publication title -
microwave and optical technology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.304
H-Index - 76
eISSN - 1098-2760
pISSN - 0895-2477
DOI - 10.1002/mop.31065
Subject(s) - ground plane , axial ratio , optics , broadband , bandwidth (computing) , circular polarization , impedance matching , coaxial , physics , patch antenna , electrical impedance , conductor , microstrip , antenna (radio) , engineering , electrical engineering , telecommunications , geometry , mathematics , quantum mechanics
This letter proposes a circularly polarized patch antenna with 3‐dB AR (axial ratio) and reasonably constant gain characteristics and low crosspolarization covering a wide bandwidth using an AGS (artificial ground structure). The AGS with a rectangular unit cell can expand the 3‐dB axial ratio of CP (circular polarization) and impedance characteristics of circularly polarized patch antennas. For achieving the broadband impedance characteristics, a matching structure is required to keep a sufficient impedance bandwidth between the two parallel resonances separated with a large ratio of frequency. As the matching structure, the outer conductor of a feeding coaxial cable passing through the ground plane is extended to be close to the radiating patch element. However, such matching structure yields large XPOL (crosspolarization) in off‐boresight directions. In this letter, the extended coaxial structure is replaced with a meandering probe for suppressing XPOL and matching impedance. The effect of the meandering probe is discussed with simulated and measured results. As a result, the proposed structure achieves a −10‐dB S 11 bandwidth of around 50% and a 3‐dB AR bandwidth of 20%, respectively. The average gain of 7.8 dBic is achieved covering the AR bandwidth. Furthermore, off‐boresight XPOL decreases by around 10 dB compared to the previous structure with the extended coaxial structure in ±30° directions.