Low Noise Radiometers for Passive Millimeter Wave Imaging
W-band passive millimeter wave imaging cameras have been developed and commercialized for security screening and rotorcraft brownout applications. The direct detection imaging modules developed at HRL Laboratories provide good sensitivity due to the high responsivity and low 1/f noise of its Sb-based backward tunnel diode detectors. Here we review results demonstrating that an NETD<0.5K can be reliably achieved without the use of Dicke switching or optical chopping. This performance is achieved using a two-MMIC chipset consisting of a low noise amplifier and matched detector. Results for detector arrays with no RF amplification will also be presented.