9 June 2014 Passive 670 GHz imaging with uncooled low-noise HEMT amplifiers coupled to zero-bias diodes
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We discuss the application of recently developed 670 GHz low-noise amplifiers based on InP HEMTs to passive indoor imaging. Packaged LNAs were integrated with commercial zero-bias diodes, and accurate measurements of system noise-equivalent temperature difference (NETD) made, using blackbody sources. The NETD values are compared with independent prior measurements (Deal et al. 2011) of LNA gain, noise figure, and bandwidth, and with cryogenic bolometer measurements made in the same test conditions. Currently, the LNA gain is not sufficient to render the ZBD noise negligible; measurements are presented that separate the two components. Low-frequency noise measurements are also presented that display the effects of 1/f noise in the ZBD and gain variations in the LNA. The implications of the low-frequency noise are discussed in terms of scanning or beam-steering strategies for an imager based on the LNAs. Raster-scanned, single-pixel images of indoor scenes are presented. They are quantitatively interpreted in terms of NETD, and angular resolution and coupling efficiency of the optics.
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E. N. Grossman, E. N. Grossman, K. Leong, K. Leong, X. B. Mei, X. B. Mei, W. R. Deal, W. R. Deal, "Passive 670 GHz imaging with uncooled low-noise HEMT amplifiers coupled to zero-bias diodes", Proc. SPIE 9078, Passive and Active Millimeter-Wave Imaging XVII, 907809 (9 June 2014); doi: 10.1117/12.2050738; https://doi.org/10.1117/12.2050738

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