Compact dual-band circularly polarized patch antennas with small frequency ratio

This paper proposes a new design for dual-band Circularly Polarized (CP) microstrip antennas. CP antennas are advantageous for indoor communications due to their intrinsic robustness to multipath. In addition, Dual-band operation is another aid for communication in the sense of reconfigurability issue. The proposed antenna is a disc patch loaded by 2 pairs of parasitic crown segments, printed on common dielectric substrate and fed by a coaxial probe. With this design, dual band configurations with small frequency ratio - from 4% to 16% - can be flexibly designed, without sacrificing the gain. By the means of a parametric characterization, which serves either as a guideline, and as the staring point for an extensive optimization, the cases ranging from 2.45/2.55 to 2.45/2.85 GHz are investigated. The validation of this approach is proven by designing and fabricating a set of prototypes implemented with common low-cost FR4 dielectric substrate. A mean Left Hand CP Gain of 4dB is measured at first operation peak, while a mean of 2.25 dB is found for the second peak for all the fabricated configurations. All the peak resonances shows at least 15 dB of polarization ratio, confirming the validity of the proposed design.