Low Noise Direct Detection Sensors for Millimeter Wave Imaging

As millimeter wave electronic component technologies have matured, passive millimeter wave (mmW) imaging using direct detection is emerging as a cost effective approach to imaging through obscuring materials such as clothing for concealed weapons detection or sand for rotorcraft landing. This paper reviews the basic operation of W band direct detection receivers, and describes progress made at HRL in the development of mmW front end IC components. InP HEMT LNAs provide high gain and low noise, appropriate for high sensitivity front ends that require relatively short integration times. Sb-based MMIC detectors provide high sensitivity and low noise, relaxing the gain requirements of the LNA. Finally, promising results of the ongoing DARPA MIATA program demonstrate reasonable sensitivity of a purely passive imaging module, the first step toward imaging without the need for LNAs