Electromagnetic Analysis of Radiometer Calibration Targets Using Dispersive 3D FDTD

Sandeep, Srikumar; Gasiewski, Albin J.

doi:10.1109/tap.2012.2194679

Cited by 23 publications

(14 citation statements)

References 11 publications

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“…Due to the coherent summation of scattering from each periodic unit, there will be directions where scattering from each units are additive, also directions where scatterings cancel with each other. Considering a normal illumination with a plane-wave like phase distribution, there will be at least one additive scattering lobe at the mirrored direction in all frequency region which is the basic Floquet mode or the backscattering lobe, and more scattering lobes will rise when the frequency is high enough so that c/f = λ < p [6][7][8]10]. The angular positions of those scattering lobes can be found based on the Floquet mode theory as in Eq.…”

Section: Emissivity Reflectivity and Scatteringmentioning

confidence: 99%

“…The FDTD is a time domain method based on discretizations of Maxwell equations in the differential form and is found to be one of the most suitable full-wave numerical solutions for modeling scattering from calibration targets [5][6][7][8][9][10]. It can be used in finding the scattering of incident beams from actualsized targets just as in the mono-static measurement configuration [8][9][10] and can also be applied in finding wideband reflectivity of the coated structure based on a infinite-sized approximation with planewave illumination [6,7,13].…”

Section: Numerical Solutions For Scattering From Calibration Targetsmentioning

confidence: 99%

“…It can be used in finding the scattering of incident beams from actualsized targets just as in the mono-static measurement configuration [8][9][10] and can also be applied in finding wideband reflectivity of the coated structure based on a infinite-sized approximation with planewave illumination [6,7,13]. Figure 3 shows the two computation configurations.…”

Section: Numerical Solutions For Scattering From Calibration Targetsmentioning

confidence: 99%

“…Actually, one of the most important challenges in improving the accuracy of microwave radiometry is raising the precision of this referencing source. For this goal, long term researches have been conducted, ranging from target designs [5,7], numerical simulations [5][6][7][8][9][10][11][12][13], measurement studies [3,[14][15][16], to recent brightness radiation modeling [16][17][18].…”

Section: Introductionmentioning

confidence: 99%

“…The second issue, however, is yet to be addressed. Due to the periodic structure of the calibration target, its scattering is constructed by scattering lobes in the upper-space, namely, Floquet modes [6][7][8]10]. In the mono-static scattering measurement, the reflectivity has to be extracted from the measured backscattering, and a correction factor is required in this case.…”

Section: Introductionmentioning

confidence: 99%

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Analysis on the Floquet Scattering Lobes From Microwave Calibration Targets

Gao¹,

Yuan²,

Jing³

et al. 2017

PIER B

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Abstract-The calibration target is a vital instrument for calibrating space-borne microwave radiometers, and its emissivity performance must be accurately determined before usage. Based on the Kirchhoff's law of thermal equilibrium, the emissivity of a calibration target can be determined from its electromagnetic reflectivity, which is defined as space integration of scattering. However, due to the general shape of periodic coated sharp pyramids, the scattering from calibration targets shows Floquet mode properties with scattering lobes in upper space. That phenomenon must be considered in the reflectivity measurement of calibration target, especially in the mono-static backscattering configuration. To support such backscattering-based reflectivity measurement, the Floquet mode and scattering patterns from periodic unit and finite-sized array are investigated by numerical simulations, more specifically, by the finite-difference time domain (FDTD) algorithm. The investigations include the scattering power distributions among scattering lobes from coated and bare pyramid arrays, and the ratio of total reflection to backscattering in cases of typical parameters. It is found in the millimeter wave region that the scattering power from bare pyramids is still concentrated in the backscattering lobe in the mono-static configuration, while for the coated pyramids the scattering power is distributed around Floquet modes. For the considered geometry and coating parameters, the power ratio of total scattering to backscattering can be more than 10 dB at the cared frequencies. After all, the numerical results provide referencing correction factor for actual measurement studies. It is also validated by numerical results and suggested in practice, to use periodic simulations of low computational burden to evaluate the compensation factor for the mono-static reflectivity measurement.

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Section: Emissivity Reflectivity and Scatteringmentioning

confidence: 99%