The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 29, 1990
Filed:
Jan. 05, 1989
Anthony Freeman, La Crescenta, CA (US);
David Blacknell, Sheffield, GB;
Shaun Quegan, Sheffield, GB;
Ian A Ward, Chelmsford, GB;
Christopher J Oliver, Malvern, GB;
Ian P Finley, St. Johns, GB;
Richard G White, Malvern, GB;
James W Wood, Malvern Link, GB;
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.