A calibration concept for passive MW imaging using beam steering by frequency shift and aperture synthesis

Eric Schreiber; Markus Peichl; Matthias Jirousek

doi:10.1117/12.2028641

18 October 2013 A calibration concept for passive MW imaging using beam steering by frequency shift and aperture synthesis

Eric Schreiber, Markus Peichl, Matthias Jirousek

Author Affiliations +

Proceedings Volume 8900, Millimetre Wave and Terahertz Sensors and Technology VI; 89000E (2013) https://doi.org/10.1117/12.2028641
Event: SPIE Security + Defence, 2013, Dresden, Germany

Abstract

Passive microwave (MW) remote sensing is used in Earth observation missions for example to estimate the salinity of oceans or the soil moisture of landscapes. In these cases the absolute brightness temperature numbers are important for sufficient accuracy of the estimated geo-physical parameters. Consequently a suitable system calibration network is required. At DLR a radiometric demonstrator for fully-electronic MW imaging was set up at Ka-band, which is based on a combination of beam steering by frequency shift using a broadband slotted-waveguide antenna for one scanning direction, and the application of aperture synthesis for the other direction. Aperture synthesis is well known from radio astronomy, but it is still a new imaging principle for Earth observation or security applications. Hence as well new calibration techniques have to be developed for this kind of scanning mechanism. In this paper a novel approach for a noise-source based calibration method taking into account the antenna losses will be introduced. When using aperture synthesis techniques to determine the absolute brightness temperature values, it is very important, among other things, to know the exact phase transfer function of the system in order to achieve the desired radiometric resolution. Consequently our approach enables phase calibration as well. The paper outlines a proof of concept for this calibration method using a two-element interferometer called VESAS (Voll Elektronischer Scanner mit AperturSynthese) as a demonstrator. The functionality of the demonstrator and the proof of concept of the imaging principle mentioned before are written in detail in [1].

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Eric Schreiber, Markus Peichl, and Matthias Jirousek "A calibration concept for passive MW imaging using beam steering by frequency shift and aperture synthesis", Proc. SPIE 8900, Millimetre Wave and Terahertz Sensors and Technology VI, 89000E (18 October 2013); https://doi.org/10.1117/12.2028641

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KEYWORDS

Calibration

Antennas

Receivers

Synthetic apertures

Temperature metrology

Medium wave

Interference (communication)

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