Method for examining an ice region or dry region using radar echo sounding

• US 8,159,384 B2
• Filed: 03/14/2008
• Issued: 04/17/2012
• Est. Priority Date: 03/29/2007
• Status: Active Grant

• Current Assignee: Deutsches Zentrum Fã¼R Luft- Und Raumfahrt E.V.
• Original Assignee: Deutsches Zentrum Fã¼R Luft- Und Raumfahrt E.V.
• Inventors: Scheiber, Rolf
• Primary Examiner(s): GREGORY, BERNARR E
• Application Number:
  US12/532,935
• Publication Number:
  US 20100171651A1
• Time in Patent Office: 1,495 Days
• Field of Search: 342/21, 342/22, 342 25 R- 25 F, 342/59, 342 73- 81, 342159-176, 342/179, 342190-197, 342368-377
• US Class Current: 342/25.F
• CPC Class Codes: G01S 13/882 for altimeters measuring height using barometric means G01C5/06
• CPC Class Codes: G01S 13/904 SAR modes
• CPC Class Codes: G01S 13/9047 Doppler beam sharpening mode
• CPC Class Codes: G01S 7/2813 Means providing a modification of the radiation pattern for cancelling noise, clutter or interfering signals, e.g. side lobe suppression, side lobe blanking, null-steering arrays specially adapted to secondary radar systems G01S13/762; aerials or aerials systems H01Q21/29, H01Q25/00
• CPC Class Codes: H01Q 3/2611 Means for null steering; Adaptive interference nulling

Abstract

To suppress cross-ambiguities in the examination of an ice region or dry region by means of aircraft- or aerospace-supported radar echo sounding, the region to be examined is overflown by a radar sensor (6) by multiple compatible radar sensors of the same operating wavelength on multiple spatially separated, substantially parallel paths, wherein the radar signal data received on each path are recorded. The radar signal data recorded for each of the different paths are summed coherently and using a weighting to form a radargram, wherein an adaptive complex-valued weighting for each of the individual paths is performed using a geometrical model which takes into account the topography of the environment of the region to be examined. The weighting for every depth of the examined region is determined by solving a system of linear equations from which is calculated a synthetic antenna pattern which has zeros in the direction of the ambiguities.

Implementation in radar systems for echo sounding in ice and in dry regions on earth or other planets and extraterrestrial objects.

Claims

1. A method for examining an ice region or dry region using radar echo sounding, wherein a radar sensor flying over the region to be examined emits radar transmission pulses in the direction of the nadir, illuminating the surface and the inner volume of the region, wherein the reflected radar pulse signals received in the radar sensor are processed and evaluated to obtain a radargram, and wherein measures are provided to suppress ambiguities, characterized in that the region to be examined is overflown by the radar sensor or by multiple compatible radar sensors of the same operating wavelength on multiple spatially separated adjacent or parallel paths and the radar signal data received on each path are recorded, that the radar signal data recorded for each of the different paths are summed coherently and using a weighting to form a radargram, wherein an adaptive complex-valued weighting for each of the individual paths is performed using a geometrical model which takes into account the topography of the environment of the region to be examined, and that the complex-valued weighting for every depth of the examined region is determined by solving a system of linear equations from which is calculated a synthetic antenna pattern which has zero points in the direction of the ambiguities.

2. The method of claim 1, characterized by a coherent Doppler processing in the form of a filtering or a so-called “

Doppler Beam Sharpening”

so as to artificially reduce the antenna pattern in the direction of flight, so that ambiguity echo signals coming from reflections in front of and behind the radar sensor are filtered out or attenuated and the signal-to-noise ratio is improved due to the coherent summation of the interesting signal portions.

3. The method of claim 1, characterized in that, when airplane-borne radar sensors are used, the implementation is performed with parallel overpasses having short spatial base lines therebetween.

4. The method of claim 1, characterized in that, with a space-borne implementation, the radar data recorded on repeated orbits of the same radar sensor or similar compatible radar sensors are evaluated.

5. The method of claim 1, characterized by the scalability of the performance of e ambiguity suppression as a function of the number of available recordings/overpasses.

6. The method of claim 1, characterized in that a calibration phase is used to take into account different propagation effects that exist primarily due to different atmospheric or ionospheric effects.

7. The method of claim 6, characterized in that the calibration phase is determined independently for each data recording from the phase of the first strong ice surface reflection at the ice surface or at the surface of the dry region to be examined.