Fourth-order-product phase difference autofocus

Details Fourth-order-product phase difference autofocus Fourth-order-product phase difference autofocus

1991-11-27

1993-04-06

Tubbesing, T. H.

Communications: directive radio wave systems and devices (e.g.,

Synthetic aperture radar

G01S 1390

Patent

active

052007545

ABSTRACT:
The present invention is a computational method, defined by a computational algorithm, that automatically corrects synthetic array radar (SAR) focus errors more accurately than conventional procedures. The novel feature is that the present method estimates residual phase errors by forming fourth-order subarray products in lieu of conventional second-order subarray products. As a result, a pull-in range for residual phase errors is vastly improved. The present invention advances the state of the art by creating a SAR autofocus method that has an unlimited pull-in range for both a quadratic and a cubic phase errors. The invention thus extends the operational range and resolution of SAR systems, and enables the effective use of the SAR sensor with a limited (less expensive) motion compensation subsystem. The present invention provides for a phase difference autofocus method that estimates the residual quadratic and cubic phase error that often requires only one autofocus iteration.

REFERENCES:
patent: 4924229 (1990-05-01), Eichel et al.
patent: 4999635 (1991-03-01), Niho
patent: 5021789 (1991-06-01), Shaw

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