Communications: directive radio wave systems and devices (e.g. – Clutter elimination
Reexamination Certificate
2003-06-04
2004-10-12
Sotomayor, John B. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Clutter elimination
C342S161000, C342S162000, C342S163000, C342S196000
Reexamination Certificate
active
06803876
ABSTRACT:
This invention relates to radar signal processing. In particular, this invention concerns Doppler processing and clutter filtering on irregular Pulse Repetition Time (PRT) sampled signal.
DESCRIPTION OF THE PRIOR ART
In conventional radar, Doppler processing uses discrete Fourier transform (DFT) on regularly sampled signals because the pulse repetition time is constant within a burst. So, such conventional processing using discrete Fourier transform (DFT) is not applicable to irregular Pulse Repetition Time (PRT) sampled signal.
Irregular Pulse Repetition Time (PRT) is usually meant to prevent blind speeds (velocity ambiguity), the jammers from locking on the radar's Pulse Repetition Time (PRT), and also to solve Doppler ambiguities.
Current work on irregular sampling is mostly motivated by image processing. Efficient algorithms based on frame operations have been developed as “Efficient numerical methods in non-uniform sampling theory” written by Feichtinger, H. G. and al in
Numerische Mathematik
69 (NUHAG). Wavelet transform in digital filter banks as “Multirate systems and filter banks” written by Vaidyanathan, P. P.
Prentice
-
Hall Publishers
(1993) illustrates efficient 1D applications with irregular samples obtained by integer decimation or expansion of uniform samples.
In Doppler radar signal processing, Pulse Repetition Time (PRT) staggering has been studied, but with emphasis on the Fourier analysis, rather than on solving the irregular-sampling problem.
An exception is the NSSL algorithm proposed in the American patent U.S. Pat. No. 6,081,221 for Doppler weather radar. This NSSL algorithm offers a non-ambiguous solution in Doppler speed and does only ground clutter filtering. Such ground clutter has a mean frequency equal to zero because it does not move. So, clutter with any mean frequency like: sea clutter or rain clutter . . . can not be filtered with this proposed NSSL algorithm.
SUMMARY OF THE INVENTION
This invention solves the above-mentioned drawbacks, in particular solving the velocity ambiguity and filtering any type of clutter, providing a deconvolution method which filter any kind of clutter even varying clutter like sea clutter, rain clutter . . .
An object of this invention is a deconvolution method of irregular pulse repetition time sampled signal x(t
m
), which comprises the following steps:
[S
1
] conversion of the irregular samples x(t
m
) to regular samples r(iT
&egr;
);
[S
2
] computation of the spectrum dft(r) of these regular samples;
[S
3
] isolation of the clutter spectra in dft(r) by assuming clutter spreads over more than a few range gates;
[S
4
] estimation of the clutter spectral lines from the mean and the width of the isolated clutter spectra;
[S
5
] subtraction of the estimated clutter spectra from the total spectrum dft(r);
[S
6
] deconvolution of the remaining spectra.
In a first embodiment of the deconvolution method, the computation in the steps of subtraction [S
5
] and deconvolution [S
6
] is adjusted to the clutter type by the clutter spectra given by step [S
3
].
A further object of this invention is deconvolution system of irregular pulse repetition time sampled signal x(t
m
), which comprises:
Mean for converting the irregular samples x(t
m
) to regular samples r(iT
&egr;
);
Mean for computing the spectrum dft(r) of these regular samples;
Mean for isolating the clutter spectra in dft(r) by assuming clutter spreads over more than a few range gates;
Mean for estimating the clutter spectral lines from the mean and the width of the isolated clutter spectra;
Mean for subtracting the estimated clutter spectra from the total spectrum dft(r);
Mean for deconvolving of the remaining spectra.
Moreover, another object of this invention is the use of such deconvolution method in radar system.
A further object to this invention is the use of such deconvolution method as clutter filtering, in particular as sea clutter filtering.
REFERENCES:
patent: 4400700 (1983-08-01), Rittenbach
patent: 4737788 (1988-04-01), Kennedy
patent: 5376940 (1994-12-01), Abatzoglou
patent: 6081221 (2000-06-01), Zrnic et al.
patent: 2004/0056794 (2004-03-01), Erkocevic-Pribic
patent: 1369703 (2003-12-01), None
“Thinned stepped frequency waveforms to furnish existing radars with imaging capability”, Freedman, A; Bose, R.; Steinberg, B.D.; Aerospace and Electronic Systems Magazine, IEEE, vol.: 11, Issue: 11, Nov. 1996 pp.: 39-43.*
“Suppressing the azimuth ambiguities in synthetic aperture radar images”, Moreira, A.;Geoscience and Remote Sensing, IEEE Transactions on, vol.:31, Issue: 4, Jul. 1993 pp.:885-895.*
“Blind deconvolution for Doppler centroid estimation in high frequency SAR”, Prati, C.; Rocca, F.; Kost, Y.; Damonti, E.;Geoscience and Remote Sensing, IEEE Trans on, vol.: 29, Issue: 6, Nov. 1991 Ps:934-941.*
Maier M.W., “Non-Uniform PRI Pulse-Doppler Radar”, Proceedings SSST, University of Alabama in Huntsville, Mar. 1993, pp. 164-168.
Chornoboy E.S., et al., “Variable-PRI Processing for Meterologic Doppler Radars”, IEEE, 1994, pp. 85-90.
Feichtinger H.G., et al., “Efficient Numerical Methods in Non-Uniform Sampling Theory”, Numerische Mathematik, Germany, 1995, pp. 423-440.
Lowe Hauptman & Gilman & Berner LLP
Sotomayor John B.
Thales Nederland B.V.
LandOfFree
Irregular PRT deconvolution method and systems, and its uses does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Irregular PRT deconvolution method and systems, and its uses, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Irregular PRT deconvolution method and systems, and its uses will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3321271