Technical Papers and Presentations

This paper presents a new design methodology of quasi-conformal transformation optics (QCTO) based modified Luneburg lens antennas using a broadband anti-reflective (AR) layer. The design used QCTO technique to modify portion of the lens’s spherical geometry into a flat surface for convenient integration of feed networks and optimize the permittivity profile to achieve original electromagnetic performances. Electromagnetic devices designed with QCTO technique usually suffer from impedance mismatches along the excitation surface due to the absence of material’s magnetic response in QCTO approximations and results in a degraded device performance. To mitigate the reflection problems and ensure a uniform impedance matching across the entire planar surface of the QCTO-enabled modified Luneburg lens antenna, we designed a new broadband AR layer along with the lens’s flat surface. The new design methodology was validated by designing an example lens to operate in the Ka-band (26GHz – 40GHz). All the designs including QCTO mapping, AR layer permittivity profile calculation were conducted using COMSOL Multiphysics^® simulation software. The lens antennas with the presence of an AR layer and conventional QCTO-enabled lenses without an AR layer were fabricated and experimentally characterized. The antenna performances of the example lenses were measured experimentally and compared with the simulated predictions conducted with 3D full-wave simulations using COMSOL Multiphysics^® simulation software. The anti-reflective layer enabled new design approach showed a good impedance matching across the entire planar excitation surface and was able to achieve a wide beamscanning angle (-55˚ to +55˚) with a high gain value at all the excitation positions over the entire Ka-band.