Unamplified direct detection W-band imaging array

We are developing a passive W-band millimeter wave imaging array that operates without the use of RF low noise amplifiers. The work is supported by the DARPA MIATA program. Previously reported Phase I results were a noise equivalent temperature difference (NETD) of 4.8°K. The goal of Phase II, currently underway, is to decrease this to 2°K or less. There are two improvements that must be made to achieve the goal. The square law diode detector sensitivity and the RF bandwidth reaching the detector must be increased significantly. This paper mainly deals with the first issue, the effort to increase the sensitivity by decreasing the diode area and capacitance, using electron beam lithography. Brief mention will be made of the redesign of the antenna-to-diode transition that simulations indicate will provide a doubling of bandwidth from 30 to 60 GHz.