Low noise radiometers for passive millimeter wave imaging

W-band passive millimeter wave imaging cameras for concealed weapons detection are being developed and commercialized for security screening and rotorcraft applications. The direct detection chipset from HRL Laboratories has become the standard for the front end because of the low noise of its Sb-based backward tunnel diode detectors and InP HEMT low noise amplifiers. Here we review recent results demonstrating that an NETD<0.5 K can be achieved without the use of Dicke switching or optical chopping using a two-MMIC chipset consisting of a low noise amplifier and matched detector. Recent results for an 8times8 imaging array with no RF amplification will also be presented, indicating an NETD of <3 K for a 30 Hz video rate.