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Rough surface wavelength measurement through self mixing of Doppler microwave backscatterA microwave backscatter technique is presented that has the ability to sense the dominant surface wavelength of a random rough surface. The purpose of this technique is to perform this measurement from an aircraft or spacecraft, wherein the horizontal velocity of the radar is an important parameter of the measurement system. Attention will be directed at water surface conditions for which a dominant wavelength can be defined, then the spatial variations of reflectivity will have a two dimensional spectrum that is sufficiently close to that of waves to be useful. The measurement concept is based on the relative motion between the water waves and a nadir looking radar, and the fact that while the instantaneous Doppler frequency at the receiver returned by any elementary group of scatterers on a water wave is monotonically changing, the difference in the Doppler frequency between any two scattering 'patches' stays approximately constant as these waves travel parallel to the major axis of an elliptical antenna footprint. The results of a theoretical analysis and a laboratory experiment with a continuous wave (CW) radar that encompasses several of the largest waves in the illuminated area show how the structure in the Doppler spectrum of the backscattered signal is related to the surface spectrum and its parameters in an especially direct and simple way when an incoherent envelope detector is the receiver.
Document ID
19800030298
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Weissman, D. E.
(Hofstra University Hempstead, N.Y., United States)
Johnson, J. W.
(NASA Langley Research Center Hampton, Va., United States)
Date Acquired
August 10, 2013
Publication Date
November 1, 1979
Publication Information
Publication: IEEE Transactions on Antennas and Propagation
Volume: AP-27
Subject Category
Instrumentation And Photography
Accession Number
80A14468
Funding Number(s)
CONTRACT_GRANT: NGR-33-209-002
Distribution Limits
Public
Copyright
Other

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