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1. (WO1985000896) SYSTEME RADAR BIDIMENSIONNEL A EXTRACTION SELECTIONNABLE DE DONNEES DE CIBLES TRIDIMENSIONNELLES
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CLAIMS

What is Claimed is:

1. A radar system (20) for a selectable three dimension or two dimension position indication of targets within the surveillance volume comprising:
an antenna (23) adapted for selectively directing a fan beam and a narrow beam wherein the narrow beam is scannable in elevation angle and has a narrower beamwidth in elevation angle than the fan beam;
a two dimension radar system (13) coupled to the antenna (23) for indicating the azimuth and range of the targets; and
an elevation angle measurement means (26) coupled to the antenna (23) and to the two dimension radar system (13) for determining the elevation position of a selected target by selecting and scanning the narrow beam, and processing reflected signals received from the selected target during the scanning of the narrow beam to indicate the elevation position of the selected target.

2. The radar system of Claim 1 wherein the narrow beam is electronically controllable to scan in elevation angle.

3. The radar system of Claim 2 wherein the antenna (23) is a planar phased array antenna.

4. The radar system of Claim 1 wherein the antenna (23) is rotatable in azimuth angle.

5. The radar system of Claim 1 wherein:
the narrow beam is sequentially scanned in a plurality of selected overlapping elevation angle positions; and
the elevation angle measurement means (26) comprises a comparator means for comparing reflected signals from the selected target in one selected
elevation angle position to reflected signals from the selected target in an overlapping elevation angle position.

6. The radar system of Claim 5 wherein the elevation angle measurement means (26) further comprises a computing means (24) for controlling the narrow beam wherein the computing means (24) determines an azimuth window about a selected target, controls the antenna (23) to select the narrow beam at the beginning of the azimuth window and controls the antenna (23) to scan the narrow beam in the overlapping elevation angle positions while in the azimuth window.

7. The radar system of Claim 6 wherein the elevation angle measurement means (26) further comprises a second computing means, coupled to the comparator means, for receiving the comparisons of reflected signals, comparing the comparisons to each other and determining the elevation position of the selected target thereby.

8. The radar system of Claim 6 wherein the
scanning of the narrow beam in elevation angle is
performed a plurality of times for the selected target and the overlapping positions of the narrow beam are varied whereby the accuracy of the indication of the elevation position of the selected target is increased.

9. The radar system of Claim 6 wherein the
computing means also determines a range window about the selected target and controls the elevation angle measurement means (26) to process only the reflected signals of targets located in the range window.

10. A radar system for a selectable three dimension or two dimension position indication of targets within the surveillance volume comprising:
a planar phased array antenna (23) adapted for selectively directing a fan beam and a narrow beam wherein the narrow beam is scannable in elevation
angle and has a narrower beamwidth in elevation angle than the fan beam;
a two dimension radar system (13) coupled to the antenna (23) for detecting and locating the position of the targets in terms of azimuth and range;
a processing means (26) coupled to the antenna and to the two dimension radar system for determining the elevation position of selected targets by selecting the narrow beam at the azimuth position of a selected target, scanning the narrow beam in a plurality of selected overlapping elevation angle positions, comparing the reflected energy from the selected target in the overlapping elevation angle positions and determining the elevation position of the selected target thereby.

11. The radar system of Claim 10 wherein the
processing means (26) also collapses the reflected
energy during the use of the narrow beam, and transmits the collapsed energy to the two dimension radar system (13) whereby the two dimension radar system (13) continues to detect and locate targets while the processing means (26) determines the elevation position of the selected target.

12. The radar system of Claim 1 wherein the
elevation angle measurement means comprises a computing means responsive to programming residing therein for determining the elevation position of the selected
target by:
initiating the programming In response to a request therefor;
determining an azimuth window about the selected target;
controlling the antenna to select the narrow beam at the beginning of the azimuth window;
scanning the narrow beam in a plurality of selected elevation positions while in the azimuth window;
determining a range cell about the selected target; and
resolving the selected target from the reflected signals received during use of the narrow beam.

13. The radar system of Claim 12 further comprising the step of selecting a particular pulse repetition frequency to minimize the probability of the selected target maneuvering into a Doppler blind region in the current scan.

14. The radar system of Claim 13 wherein the step of selecting a particular pulse repetition frequency (PRF) comprises choosing the PRF which maximizes the distance between the selected target Doppler and the closest Doppler blind.

15. The radar system of Claim 12 wherein the step of scanning the narrow beam in a plurality of selected elevation positions comprises selecting the elevation positions so that the distance from the target to the crossover point of two beams is minimized.

16. The radar system of Claim 12 wherein the step of resolving the selected target comprises collapsing the reflected signals received during use of the narrow beam to form two dimension target plots and correlating the target plots with the reflected signals received from the selected target during use of the narrow beam.

17. The radar system of Claim 16 wherein the step of correlating comprises correlating the range cell and azimuth position of the selected target with the target plots.