A Miniaturized Wideband Circularly Polarized Antenna Based on Tightly Coupled Monopole

This letter presents a miniaturized wideband circularly polarized (CP) antenna based on a tightly coupled monopole operating in the ultra high frequency (UHF) band. Initially, a tightly coupled wideband monopole is employed as the radiation unit, showcasing its potential for broadband operation. A two-layer compact wideband sequential feed network (WSP) is then designed to connect these elements, featuring a higher efficiency compared to the one employing the low-temperature co-fired ceramic technology (LTCC) technology. As a result, the antenna was reduced to 0.08λ
₀
in height and 0.15λ
₀
in diameter, offering practical advantages in terms of installation and form factor. Finally, the rotation direction of radiation elements is analyzed to achieve a stable beamwidth. The proposed antenna is fabricated and tested. The results demonstrate that the antenna attains a wide impedance bandwidth and axial-ratio (AR) bandwidth of approximately 80% (VSWR < 2.0) and 67% (AR < 3 dB), respectively. Additionally, a stable radiation pattern is obtained throughout the entire operating band.