Communications: radio wave antennas – Antennas – Balanced doublet - centerfed
Patent
1982-03-18
1985-04-02
Tubbesing, T. H.
Communications: radio wave antennas
Antennas
Balanced doublet - centerfed
343 5W, 343 172PC, G01S 1390
Patent
active
045090483
ABSTRACT:
A synthetic aperture radar (10) is employed for .DELTA.k measurement of ocean current from a spacecraft (11) without the need for a narrow beam and long observation times. The SAR signal is compressed (12) to provide image data for different sections of the chirp bandwidth, equivalent to frequencies f.sub.1 (t.sub.a,t), f.sub.2 (t.sub.a,t) . . . f.sub.n (t.sub.a,t), and a common area for the separate image fields is selected (14). The image for the selected area at each frequency is deconvolved (16) to obtain the image signals for the different frequencies (f.sub.1, f.sub.2 . . . f.sub.n) and the same area. A product of pairs of signals is formed (18, 20), Fourier transformed (22) and squared (24). The spectrum thus obtained from different areas for the same pair of frequencies f.sub.jk, f.sub.j+n,k are added (26) to provide an improved signal to noise ratio. The shift of the peak from the center of the spectrum is measured and compared (28) to the expected shift due to the phase velocity of the Bragg scattering wave. Any difference is a measure of current velocity v.sub.c (.DELTA.k).
REFERENCES:
patent: 4053886 (1977-10-01), Wright et al.
patent: 4101891 (1978-07-01), Jain et al.
patent: 4172255 (1979-10-01), Barrick et al.
Robert H. Stewart et al., "HF Radio Measurements of Surface Currents" Jun. 8, 1974, pp. 1039-1049, Deep Sea Research 1974, vol. 21.
Jain, A. (1977), "Determination of Ocean Wave Heights from Synthetic Aperture Radar Imagery," Applied Physics, vol. 13, pp. 371-372.
Schuler, D. L. (1978), "Remote Sensory of Directional Gravity Wave Spectrum and Surface Currents Using Microwave Dual-Frequency Radar," Radar Sciences vol. 13, pp. 321-331.
Plant, W. J. and Schuler, D. L. (1980), "Remote Sensing of the Sea Surface Using One- and Two-Frequency Microwave Techniques," Radar Sciences, vol. 15, pp. 605-615.
Jones Thomas H.
Manning John R.
McCaul Paul F.
Sotomayor John B.
The United States of America as represented by the Administrator
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