A Compact Dual-Band Omnidirectional Circularly Polarized Filtering Antenna for UAV Communications

A compact, low-profile, dual-band (2.4/5.8 GHz) omnidirectional circularly polarized (CP) antenna for consumer Unmanned Aerial Vehicle (UAV) communications is proposed. Given the constraints of UAV installation, we incorporate complex miniaturization etching techniques into the antenna design. The low-frequency resonance is primarily realized by four short-terminated arcs, while the high-frequency resonance is predominantly induced by four open-terminated branches. In addition, a dual-band coupled strip-line filter is cascaded to the radiator, enhancing the design's bandwidths. A prototype of the antenna is simulated, fabricated, and measured, resulting in final dimensions of 0.2 x 0.2 x 0.042 lambda(3)(0) (lambda(0) is the free-space wavelength at 2.4 GHz). The -10 dB |S-11| and 3 dB Axial Ratio (AR) overlapped bandwidths reach 40 and 125 MHz for the low- and high-frequency bands, respectively. Lastly, we present an example of integrating the antenna into a quadcopter UAV and briefly discuss the potential of applying this antenna for a Multiple-Input, Multiple-Output (MIMO) system.