Fully polarimetric passive W-band millimeter wave imager for wide area search

Jonathan Tedeschi; Bruce Bernacki; Dave Sheen; Jim Kelly; Doug McMakin

doi:10.1117/12.2023390

27 September 2013 Fully polarimetric passive W-band millimeter wave imager for wide area search

Jonathan Tedeschi, Bruce Bernacki, Dave Sheen, Jim Kelly, Doug McMakin

Proceedings Volume 8873, Polarization Science and Remote Sensing VI; 88730V (2013) https://doi.org/10.1117/12.2023390
Event: SPIE Optical Engineering + Applications, 2013, San Diego, California, United States

Abstract

We describe the design and phenomenology imaging results of a fully polarimetric W-band millimeter wave (MMW) radiometer developed by Pacific Northwest National Laboratory for wide-area search. Operating from 92–94 GHz, the W-band radiometer employs a Dicke switching heterodyne design isolating the horizontal and vertical mm-wave components with 40 dB of polarization isolation. Design results are presented for both infinite conjugate off-axis parabolic and finite conjugate off-axis elliptical fore-optics using optical ray tracing and diffraction calculations. The received linear polarizations are down-converted to a microwave frequency band and recombined in a phase-shifting network to produce all six orthogonal polarization states of light simultaneously, which are used to calculate the Stokes parameters for display and analysis. The resulting system performance produces a heterodyne receiver noise equivalent delta temperature (NEDT) of less than 150m Kelvin. The radiometer provides novel imaging capability by producing all four of the Stokes parameters of light, which are used to create imagery based on the polarization states associated with unique scattering geometries and their interaction with the down welling MMW energy. The polarization states can be exploited in such a way that man-made objects can be located and highlighted in a cluttered scene using methods such as image comparison, color encoding of Stokes parameters, multivariate image analysis, and image fusion with visible and infrared imagery. We also present initial results using a differential imaging approach used to highlight polarization features and reduce common-mode noise. Persistent monitoring of a scene using the polarimetric passive mm-wave technique shows great promise for anomaly detection caused by human activity.

Citation Download Citation

Jonathan Tedeschi, Bruce Bernacki, Dave Sheen, Jim Kelly, and Doug McMakin "Fully polarimetric passive W-band millimeter wave imager for wide area search", Proc. SPIE 8873, Polarization Science and Remote Sensing VI, 88730V (27 September 2013); https://doi.org/10.1117/12.2023390

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