US 5,177,487 A · Sea velocity evaluator

Abstract

Sea clutter can be removed from radar signals by accurately determining sea velocity in a coverage area of a radar scan, updating a median value for the coverage area, and selecting a clutter rejection filter for the coverage area biased on the median value for the coverage area. Preferably, a median sea velocity is stored for each coverage area, as the median value. When processing begins for a coverage area, a previously stored median sea velocity is retrieved and updated. The median sea velocity is updated by converting the median sea velocity into a median phase difference between two echo signals, based upon carrier frequency and the time between receipt of two echo signals, which is preferably more than one interpulse period. The difference in phase between the two echo signals is compared with the median phase difference and the median sea velocity is increased if the median phase difference is smaller and decreased if the median phase difference is larger. A rejection filter is selected based upon the previously stored median sea velocity (preferably after adjustment based on the carrier frequency) to remove the echoes from the sea from the radar echo signals.

Claims18

Dependent claims

A method for determining radial sea velocity from radar echo signals, said method comprising the steps of:

(a) dividing a radar scan into a plurality of coverage areas;
(b) computing the radial sea velocity for each of the coverage areas based on the radar echo signals received therefrom, said computing computes a median radial sea velocity for each of the coverage areas;
and
(c) storing the median radial sea velocity for each of the coverage areas.

1 more element

An apparatus for removing sea clutter from radar echo signals, the radar echo signals spaced apart by a variable interpulse period, said apparatus comprising:

phase detection means for determining an undelayed phase value of preceding and subsequent radar echo signals;
first storage means for storing the undelayed phase value of the preceding radar echo signal to delay the undelayed phase value by at least one interpulse period to produce a stored phase value of the preceding radar echo signal;
phase difference detection means for detecting a measured phase difference between the undelayed phase value of the subsequent radar echo signal and the stored phase value of the preceding radar echo signal, and for outputting sea clutter information corresponding to the measured phase difference;
second storage means for storing median sea clutter information;
comparison means for comparing the sea clutter information with the median sea clutter information and for producing a comparison result;
update means for updating the median sea clutter information stored in said second storage means based on the comparison result;
and
removal means for removing the sea clutter based upon the median sea clutter information stored in said second storage means.

5 more elements

Dependencies are inferred from the claim text.

Sea velocity evaluator

Life of this patent

Sea velocity evaluator

Life of this patent

Abstract

Claims18