An investigation of a 110-wavelength EHF waveguide lens

Expanded aluminum honeycomb with a nominal cell width of 0.156 in was used to fabricate a 24-in diameter unzoned lens for operation at 55 GHz. The lens exhibits good focusing properties but its efficiency of only 18 percent reflects significant random phase errors. These errors are shown to result mainly from variations of the cell width. From the measured radiation characteristics the average width of the cells is deduced to be 0.161 in with a standard deviation of 0.003 in. Since phase errors associated with variations of the cell width are proportional to the lens thickness, it is deduced that the much thinner zoned lenses fabricated from this material would exhibit efficiencies approaching 50 percent.