Inexpensive and compact imaging systems with high sensitivity are needed for millimeter waves. In this study, the calculated efficiencies of elementary integrated-circuit feed antennas show that the antennas with substrate lenses are potentially better feeds than those without substrate lenses. Planar Schottky diodes are integrated with bow-tie antennas to form a one dimensional array. The energy is focused onto the antenna through a silicon lens placed on the back of the gallium-arsenide substrate. Putting a polystyrene cap on the silicon lens has been demonstrated to be an effective way to reduce the reflection loss. A self-aligning process together with proton isolation has been developed to make the planar Schottky diodes with a 1.1-THz zero-bias cutoff frequency. The antenna coupling efficiency and imaging properties of the system are studied by video detection measurements at 94 GHz. As a heterodyne receiver, a double-sideband mixer conversion loss of 11.2 dB and noise temperature of 3770°K have been achieved at a local oscillator frequency of 91 GHz.
