Title :
Millimeter-Wave Transmitarrays for Wavefront and Polarization Control
Author :
Pfeiffer, Carl ; Grbic, A.
Author_Institution :
Dept. of Electr. Eng. & Comput. Sci., Univ. of Michigan at Ann Arbor, Ann Arbor, MI, USA
Abstract :
Two separate transmitarrays that operate at 77 GHz are designed and fabricated. The first transmitarray acts as a quarter-wave plate that transforms a linearly polarized incident wave into a circularly polarized transmitted wave. The second transmitarray acts as both a quarter-wave plate and a beam refracting surface to provide polarization and wavefront control. When the second transmittarray is illuminated with a normally incident, linearly polarized beam, the transmitted field is efficiently refracted to 45 °, and the polarization is converted to circular. The half-power bandwidth was measured to be 17%, and the axial ratio of the transmitted field remained below 2.5 dB over the entire bandwidth. Both designs have a subwavelength thickness of 0.4 mm (λ°/9.7). The developed structures are fabricated with low-cost printed-circuit-board processes on flexible substrates. The transmitarrays are realized by cascading three patterned metallic surfaces (sheet admittances) to achieve complete phase control, while maintaining high transmission. Polarization conversion is accomplished with anisotropic sheets that independently control the field polarized along the two orthogonal axes. The structures are analyzed with both circuit- and fields-based approaches.
Keywords :
millimetre wave antenna arrays; phase control; transmitting antennas; anisotropic sheets; circuit-based approach; circularly polarized transmitted wave; fields-based approach; flexible substrates; frequency 77 GHz; millimeter-wave transmitarrays; phase control; polarization control; polarization conversion; polarized incident wave; printed-circuit-board processes; quarter-wave plate; size 0.4 mm; transmittarray; wavefront control; Admittance; Bandwidth; Lenses; Optical retarders; Phase control; Polarization; Beam forming; circular polarization; metasurface; millimeter wave; reflectarray; sheet impedance; transmit array;
Journal_Title :
Microwave Theory and Techniques, IEEE Transactions on
DOI :
10.1109/TMTT.2013.2287173