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This communication proposes an additively manufactured metal-only millimeter-wave dual circularly polarized (CP) reflectarray with independent control of polarizations. A metal-only right-hand CP (RHCP) antenna is designed and used as the reflectarray’s phase-shifting unit cell (UC). The RHCP UC is immune to the LHCP incidence, and the UC directly reflects the LHCP incidence into free space. Thus, the phase shifting of the LHCP wave solely depends on the rotation angle of the UC. For the RHCP incidence, it is received by the RHCP UC first and induced into the metal waveguide. Then, the energy is reflected by the ground of the metal waveguide and reradiated into free space with RHCP. Thus, the phase shifting of the RHCP wave is determined by the rotation angle of the UC and the length of the metal waveguide. By properly selecting the rotation angle of the UC and the length of the metal waveguide, RHCP and LHCP can be independently manipulated. To demonstrate, two reflectarray antennas with different LHCP and RHCP beam directions are fabricated using additive manufacturing and experimentally verified. [ABSTRACT FROM AUTHOR]

A wideband circularly polarized (CP) 2-arm spiral antenna is designed for 60-GHz applications in this letter. The proposed antenna is implemented on a single layer with spiral printed on the top surface of the substrate and fed in a differential way through 2 metallized via holes. Unidirectional radiation is achieved thanks to the presence of the ground plane, which is placed with a distance of one-quarter of the guided wavelength to the spiral. A cavity is mounted on the top of the spiral antenna to suppress the surface wave propagate along the substrate as well as to improve the antenna gain. Experimental results show that the prototype achieves the −10-dB impedance bandwidth from 55.2 to 66 GHz with circular polarization. The peak gain at boresight is 9.5 dBi occurring at 63 GHz and the radiation patterns are stable over the operating frequency band. [ABSTRACT FROM AUTHOR]

A novel frequency-independent printed quadrifilar helix antenna with wideband performance is presented in this paper. The proposed antenna utilizes four simple gradient microstrip lines as radiators, which are wrapped around a thin cylindrical dielectric substrate. Each microstrip line has etched two slots. The introduction of the slots results in a reduced frequency interval between two resonances, making the proposed antenna achieve a wideband characteristic. In addition, the input impedance of the proposed antenna is extracted for parametric analysis. The change rule of the real and imaginary parts of the input impedance indicates that the position of the slot at below (top) could control the lower (upper) resonance point independently. A prototype is simulated, fabricated, and measured for demonstration. The measured impedance bandwidth of the proposed antenna is 42.6% from 1.09 to 1.68 GHz. Moreover, a feeding network adopting a chip balun and two chip hybrid couplers is designed to measure the radiation pattern and axial ratio of the proposed antenna. Finally, the wideband, frequency-independent, wide half-power beamwidth, and excellent circularly-polarized characteristics make the proposed antenna become a competitive candidate in the satellite communication and navigation and positioning systems. [ABSTRACT FROM AUTHOR]

This communication presents new designs of dual-circularly polarized (CP) planar aperture antenna and array for 60 GHz applications. First, a four-port planar aperture antenna with its feeding network is developed that exhibits wide impedance bandwidth, dual-CP radiation as well as high gain. Then, based on the proposed antenna, a new scheme of building a dual-CP array is proposed. With this new scheme that combines the power splitting network and series feeding method, four sequentially fed antenna elements are successfully combined to form a CP radiation array. The experimental results show that the −10 dB impedance bandwidths of the antenna and the array are more than 18.2% (55–66 GHz). While the 3 dB axial ratio bandwidths are from 54.2 to 64.3 GHz (17.2%) for the antenna and from 54.8 to 65 GHz (17%) for the array. The maximum gains achieved are 13.7 and 17.85 dBic for the antenna and array, respectively. [ABSTRACT FROM PUBLISHER]