DocumentCode :
786371
Title :
2-D phase unwrapping and instantaneous frequency estimation
Author :
Spagnolini, Umberto
Author_Institution :
Politecnico di Milano, Italy
Volume :
33
Issue :
3
fYear :
1995
fDate :
5/1/1995 12:00:00 AM
Firstpage :
579
Lastpage :
589
Abstract :
The phase of complex signals is wrapped since it can only be measured modulo-2π; unwrapping searches for the 2π-combinations that minimize the discontinuity of the unwrapped phase, as only the unwrapped phase can be analyzed and interpreted by further processing. Given an estimate of the phase gradient (i.e., of the instantaneous frequency), the 2-D unwrapped phase can be obtained as a solution of a variational problem. The analysis of unwrapping is done quite separately from instantaneous frequency estimation so that the reliability of both steps can be assessed independently. Various methods for evaluating 2-D instantaneous frequency are presented and compared in the presence of noise and amplitude variations. A study has also been made on aliasing arising in areas where, with respect to instantaneous frequency, spatial sampling is insufficient. The presence of noise in the data further complicates phase aliasing analysis since there is no way to distinguish between the aliasing due to noise or that due to steep phase slopes
Keywords :
geophysical signal processing; geophysical techniques; image processing; radar applications; radar imaging; radar signal processing; remote sensing; remote sensing by radar; seismology; 2D phase unwrapping; complex signal; geophysical signal processing; image processing; instantaneous frequency estimation; land surface; measurement technique; phase gradient; radar remote sensing; seismology; terrain mapping; two dimensional phase unwrapping; Frequency estimation; Frequency measurement; Least squares approximation; Narrowband; Phase estimation; Phase measurement; Phase noise; Signal analysis; Signal processing; Tomography;
fLanguage :
English
Journal_Title :
Geoscience and Remote Sensing, IEEE Transactions on
Publisher :
ieee
ISSN :
0196-2892
Type :
jour
DOI :
10.1109/36.387574
Filename :
387574
Link To Document :
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