An Ultracompact Shared-Radiator Electrically Small Huygens Dual-Circularly-Polarized Antenna

A novel electrically small shared-radiator Huygens dual-circularly-polarized (HDCP) antenna is developed that features an ultracompact size, i.e., π (0.12 λc)2 × 0.06 λc = 0.0027 λc3 (ka = 0.78) at 915 MHz. A shared-radiator is formed by a pair of orthogonally placed Huygens linearly-polarized (HLP) antennas. HDCP beams, i.e., left-hand CP (LHCP) and right-hand CP (RHCP) Huygens beams, can be simultaneously excited by an '8'-shaped feed-line as the driven element. To compensate for the inductive impedance, an innovative and compact LC matching network is developed to match both ports to standard 50 Ω transmission lines. The measured results of the prototype agree reasonably with the simulated ones. The results showcase a good isolation lower than -16 dB between the two input ports and a wide measured (simulated) 3-dB AR beamwidth of 120° (144°). Additionally, the measured peak realized gain values for LHCP and RHCP beams are consistent, e.g., 2.8 dBic and 2.6 dBic, respectively. As an ultracompact DCP antenna, it is an ideal candidate for wireless applications that require DCP performance along with compact system size, e.g., battery-free IoT ecosystems with simultaneous wireless power and data transmission.