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:
Jan. 13, 1998
Filed:
Apr. 24, 1996
David A Whelan, McLean, VA (US);
Henry L McCord, Los Angeles, CA (US);
Hughes Electronics, Los Angeles, CA (US);
Abstract
A passive imaging system that uses an antenna having two antenna elements. The system cross-correlates received signals with a reference function to achieve high resolution. The antenna elements are rectangular with their long dimensions oriented normal to the longitudinal axis of a carrying vehicle and the elements are separated by a distance consistent with image resolution requirements. Additionally, the antenna elements are frequency scanned in the cross-track dimension. The channel for the forward antenna element has a time delay relative to that of the rear antenna element. This time delay achieves pointing of the antenna at a particular forward angle relative to the normal to the velocity vector. Outputs of IF filters of the antenna elements are synchronously detected to provide in-phase and quadrature (I/Q) components of their phase modulated product. These I/Q components are processed by an analog-to-digital converter and digitally filtered to select a phase modulation frequency band about the chosen forward angle. The real pan of the output of the digital filter is stored and is the cross-track channel signal is cross-correlated with the reference function. The output of this cross-correlation provides high along-track resolution with suppressed along-track sidelobe responses. The reference function is a weighted, limited-extent, replica of the real pan of the phase of a small-area signal as such signal passes through the forward angle. The reference function weighting suppresses correlation function sidelobes and is adjusted to include a component introduced by the bandwidths of the IF receivers, the angle extent that is used, and the separation between the antenna elements. A separate set of processing circuits is provided in parallel for each cross-track image channel at the output of the intermediate frequency (IF) amplifiers of both antenna elements. A fixed bandwidth is provided in each cross-track image channel, but the center frequency is different in order to point the beams of the antenna elements at a chosen cross-track position.