Huy Hung Tran

Single-Feed, Wideband, Circularly Polarized, Crossed Bowtie Dipole Antenna for Global Navigation Satellite Systems

A wideband circularly polarized (CP) antenna with a single feed is proposed for use in global navigation satellite systems. Its primary radiation elements are composed of two orthogonal bowtie dipoles, which are equipped with double-printed vacant-quarter rings to allow direct matching of the antenna to a single 50-Ω coaxial line and to produce CP radiation. The crossed bowtie dipole is appropriately incorporated with a planar metallic reflector to produce the desired unidirectional radiation pattern as well as to achieve a wideband characteristic in terms of impedance matching and axial ratio (AR) bandwidths. The designed antenna was fabricated and measured. The prototype antenna with an overall 1.2-GHz frequency size of 0.48 λo×0.48 λo×0.25 λo produced a measured |S11| 93%) over the operational bandwidth.

Circularly Polarized Bandwidth-Enhanced Crossed Dipole Antenna With a Simple Single Parasitic Element

A method of using a simple single parasitic element to significantly enhance a 3-dB axial-ratio (AR) bandwidth of a crossed dipole antenna is presented. This approach is verified by introducing one bowtie-shaped parasitic element between two arms of crossed bowtie dipoles to generate additional resonance and thereby significantly broadening AR bandwidth. The final design, with an overall size of 0.79 <italic>λ_o</italic> × 0.79 <italic> λ_o</italic> × 0.27 <italic>λ_o</italic> (<italic>λ_o</italic> is the free-space wavelength of circular polarized center frequency), resulted in very large measured –10-dB impedance and 3-dB AR bandwidths ranging from 1.9 to 3.9xa0GHz (∼68.9%) and from 2.05 to 3.75xa0GHz (∼58.6%), respectively. In addition, the antenna also yielded a right-hand circular polarization with stable far-field radiation patterns and an average broadside gain of approximately 8.2xa0dBic.

Wideband and Multipolarization Reconfigurable Crossed Bowtie Dipole Antenna

A simple design of a wideband antenna with the capability of switching its operation among five polarization states is proposed. The primary radiator consists of two bowtie dipoles arranged orthogonally through double printed rings. The polarization-reconfigurability is realized by electronically switching three p-i-n-diode pairs. By controlling the current paths from the feeding coaxial line to each dipole arm and among these arms, the antenna can change its radiation among circular polarization (CP) with both rotating senses and linear polarization at three different angles, namely, 0°, 90°, and 45°. The fabricated prototype exhibits an impedance bandwidth (BW) of 37.1% from 2.2 to 3.2 GHz for all polarization states. The axial ratio BW for both CP states is 50.4%, covering the above frequency range. A measured realized gain of greater than 6.6 dBi and a radiation efficiency of around 80% over the overlapped BW are achieved for all states.

Wideband high gain circularly polarized Fabry-Perot Resonator antenna with asymmetric superstrates

A method of using multiple dielectric slabs with small-footprint to design wideband circularly polarized Fabry-Perot Resonator antenna is presented. This approach employed two thin truncated dielectric slabs as partially reflecting surface (PRS) with positive reflection phase gradient, which can significantly improve the 3-dB gain as well as axial ratio (AR) bandwidths of the antenna. The proposed design with the very compact size of 1.5 × 1.5 × 0.7 λo3 yielded impedance matching, and axial ratio bandwidths are approximately 63.3% and 48.1%, respectively. Additionally, the proposed antenna achieved a 3-dB gain bandwidth of 58.8% with a peak gain of 15 dBi.