Environmental Research Institute of Michigan

General Dynamics Advanced Information Systems, Inc.

Erim International, Inc.

Walter G Carrara

Anthony M Tai

Ron S Goodman

Mark A Ricoy

Rondal S Goodman

Jack L Walker

Ivan J LaHaie

Ivan Cindrich

An along-track alignment and formatting system (ATAFS) formats synthetic aperture radar (SAR) data to align and format signals from scatterers in a scene to achieve an ideal data format in the along-track dimension in which such ideal data format leads to improved image quality of an image based on the SAR data and/or reduced computational burden for generating an image based on the SAR data. Two aspects of the ATAFS include: 1) the division of data stabilization into two distinct steps; and 2) the along-track (or slow-time) migration of signal support of scatterers as a function of their along-track location. A suite of SAR image formation algorithms use the ATAFS in conjunction with conventional signal processing stages to transform input coherent signal data into a complex image with image quality and geometric accuracy commensurate with the inherent information content of the input data.

Method and system for providing along-track alignment and formatting of synthetic aperture radar (SAR) data, and SAR image formation algorithms using such method and system

A method of performing the computer-intensive initial steps of the range migration algorithm, or RMA, produces radar imagery of higher quality than the current polar format (PF) processing approach, while operating faster and more efficiently than the standard RMA. The new method is advantageous when the synthetic aperture length required to achieve azimuth resolution is significantly larger than the azimuth extent of the processed scene. The method subdivides the signal history into a plurality of non-overlapping subapertures, adds a low bandwidth azimuth chirp across each subaperture and applies a fast Fourier transform separately to each subaperture. The results are coherently combined, after which the remaining steps of the conventional RMA may be completed with minor modifications to the subsequent two-dimensional phase compensation. The invention is applicable to spotlight, stripmap and scan-mode SAR image formation, and the separate, subaperture Fourier transformations may be performed simultaneously.

Subchirp processing method

A passive detection and imaging system employs interferometric and synthetic aperture techniques. A moving platform employs a pair of sensors which receive thermal electromagnetic radiations from an area of interest. The received signals are narrow band filtered by a bank of filters covering an extended bandwidth. Signals from similar narrow bands from different sensors are correlated. The plurality of frequencies and plurality of positions relative to the area of interest due to the platform motion enable generation of an inverse Fourier transform image which is resolvable in both azimuth and range. Separate preferred embodiments operating at microwave frequencies and optical frequencies are disclosed. An achromatic optical interferometric correlation technique is also disclosed.

Passive interferometric imaging receiver system

A method for range-Doppler imaging of rotating objects or of stationary scenes being tracked by a sensor carried by a moving vehicle includes the transmission and reception of sequential modulated signals, coherent demodulation of the received signals, recording of the demodulated signals, and a two-dimensional processing of the recorded signals to obtain a spatial image of the scene. In the disclosed inventive concept, the demodulated signals are recorded in a two-dimensional polar format wherein the angular coordinate of the signal on the recording medium is proportional to the relative angular position of the object or scene being imaged and the radial coordinate of the signal on the recording medium is proportional to the transmitted signal frequency within each transmitted pulse.

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Ann Arbor, MI, United States of America

Walter G Carrara