High-Gain Circularly Polarized Antenna Based on Orthogonal Dual-Function Magnetic Dipoles

This communication presents a novel circular-polarized (CP) antenna using two orthogonal bowtie loops as dual-function magnetic dipoles, which simultaneously radiate and excite parasitic patches. This dual-function mechanism expands the effective aperture while maintaining a uniform electric-field distribution, thereby achieving excellent gain performance. 90° phase difference between the two dipoles is achieved by tuning the loop lengths, while the patch size is optimized to balance radiation magnitude of the two polarizations. Consequently, the antenna element achieves a wide axial ratio (AR) bandwidth of 24% and a peak gain of 11 dBi. Based on this element, an 8 × 8 CP antenna array is developed and fabricated, incorporating a surrounding strip to suppress the mutual coupling and preserve CP purity. Measurement results agree well with the simulations, demonstrating an overlapped bandwidth (S₁₁ < -10 dB and AR < 3 dB) of 20.6%, a peak gain of 27.5 dBi, and an aperture efficiency of 85% at 30 GHz. The high directivity and circular polarization characteristics make this antenna array a promising candidate for high-quality point-to-point millimeter-wave communication applications. © 1963-2012 IEEE.