Matched, Low-Loss, and Wideband Graded-Index Flat Lenses for Millimeter-Wave Applications

Low reflection, low-loss, and wideband graded-index (GRIN) flat artificial dielectric lenses utilizing GRIN antireflection (AR) layers are developed in this paper. The GRIN lens and the AR layers are realized by perforating regular microwave substrates. The resulting reflectance, transmittance, and dielectric losses of the designed lens are 0.06% (-32.2 dB), 96.7% (-0.14 dB), and 3.3% (-14.8 dB), respectively. This highly efficient lens is designed to collimate a commercial pyramidal horn at 34.3 GHz. Excellent agreement is observed between the simulated and measured results. The flat lens decreases the half-power beamwidth of the horn from 10° to 6° and increases the peak gain by an average of 5 dB within the frequency range of 26-39 GHz.