Abstract

Millimeter systems have evolved as scaled-down versions of existing microwave technology.¹ As the operating wavelength decreases, the components become smaller, more difficult to build, and very expensive. At these high frequencies, waveguide and transmission lines become lossy and are restricted in the power they can carry. Optical components, like lenses, can be used to overcome many of these problems. A typical quasi-optical system might consist of a primary lens which focuses radiation onto a secondary substrate lens.¹ On the back side of the substrate lens sits an antenna which couples the incident radiation into a small detector. Calculations made using a modified diffraction integral predict efficiencies as high as 70% for infinitesimal dipoles in these systems. In practice bow-tie antennas are used because of their broadband properties. Measurements and calculations for the bow-tie show several interesting phenomena. Log-periodic antennas have also been studied and show excellent performance. Quasi-optical design can be extended to multielement imaging systems. Arrays of bow-ties have been analyzed, fabricated, and measured.² A major difficulty in an array is accessing the signal from each element. This problem can be avoided by using an array in which each element has its own lens. The lens has the effect of magnifying the size of the receiving antenna allowing smaller antennas to be used. This frees up more space on the substrate for running wires to each element.

© 1986 Optical Society of America