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Application of Coherence Theory to Modeling of Blackbody Radiation at Close Range



Dazhen Gu, Dave K. Walker


We apply the coherence-propagation theory to model the radiation generated by a planar passive thermal source of any state of coherence. Of our particular interest is the blackbody calibration source with partially coherent characteristic that produces the radiant intensity with its angular distribution following the Lambert's cosine law in the far field. A closed-form expression of the Poynting vector of the electromagnetic field is obtained from the theoretical framework. The formulation exhibits a straightforward manner that links the radiation field to the correlation function of the sources, though numerical computation of the Poynting vector involves evaluation of a quadruple integral and is difficult to implement directly. To tackle the challenges in numerical calculation, we have made a few mathematical adjustments, including reformulation in the angle-impact notation and various simplification on the integration, to develop a feasible scheme for improved computational efficiency. The coherence property of the blackbody source is shown to possess influential impacts on the radiation arising from such a source, especially in the near-field range where most measurements on the radiation take place in a practical system. The theory and the technical approaches provide a systematic and reliable way to quantify the Poynting vector radiated by the blackbody source in a microwave remote-sensing radiometer.
IEEE Transactions on Microwave Theory and Techniques


Blackbody target, coherence tensor, Lambertian source, microwave radiometry, partial coherence, Poynting vector.


Gu, D. and Walker, D. (2015), Application of Coherence Theory to Modeling of Blackbody Radiation at Close Range, IEEE Transactions on Microwave Theory and Techniques, [online], (Accessed July 12, 2024)


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Created May 5, 2015, Updated January 27, 2020