Anthony W Freeman

US Patent:

54899079, Feb 6, 1996

Filed:

Sep 23, 1994

Appl. No.:

8/311743

Inventors:

Manfred Zink - Wessling, DE
Herwig ttl - Germering, DE
Anthony Freeman - Pasadena CA

Assignee:

Deutsche Forschungsanstalt fur luft- und Raumfahrt e.V. - Koln

International Classification:

G01S 1390

US Classification:

342 25

Abstract:

In an airborne SAR system for determining the topography of a terrain, two complete, correlated SAR images with different amplitude modulation in the cross-track direction are obtained and recorded by switching of two antenna patterns which can be generated by means of a monopulse antenna. The desired terrain information is extracted from the amplitude relationship of the two SAR images. It is furthermore possible to extract the terrain information from polarimetric SAR data via crosstalk parameters.

US Patent:

49299506, May 29, 1990

Filed:

Jan 5, 1989

Appl. No.:

7/293599

Inventors:

Anthony Freeman - La Crescenta CA
David Blacknell - Sheffield, GB2
Shaun Quegan - Sheffield, GB2
Ian A. Ward - Chelmsford, GB2
Christopher J. Oliver - Malvern, GB2
Ian P. Finley - St. Johns, GB2
Richard G. White - Malvern, GB2
James W. Wood - Malvern Link, GB2

Assignee:

The General Electric Company, plc - London
The Secretary of State for Defence in Her Britannic Majesty's Government
of the United Kingdom of Great Britain and Northern Ireland - London

International Classification:

G01S 1390

US Classification:

342 25

Abstract:

In a synthetic aperture radar system, information concerning the radar reflectivity of a point on the ground is placed in an image at an azimuthal (cross-range) position which corresponds to the position of zero Doppler frequency shift of the received signal, under the assumption that the antenna has followed a straight line trajectory. In practice, the antenna trajectory will undergo small deviations about this straight line path which are not taken into account in the azimuth processing and which, consequently, cause incorrect azimuthal positioning in the image of the information concerning a point target on the ground. The invention uses the value of the slope of the frequency modulation of the received signal, calculated by means of an autofocus procedure, to determine the intercept of this frequency modulation at successive azimuth positions. This true intercept value is then incorporated in the azimuth processing, instead of the assumed intercept of the frequency modulation, allowing imagery which is free from azimuthal positioning errors to be produced.