Raytheon Company

Jon H Sherman

Ralph E Hudson

John P Kilkelly

Helen L Sun

Provided is a non-statistical method for compressing and decompressing complex SAR data derived from reflected energy. The method includes selecting a first FFT to provide a target ratio of pixel spacing to resolution. A second FFT is then selected which is smaller than the first FFT. The data is zero-padded to fill the second FFT and transformed to provide at least one transfer frequency. This transfer frequency is then transferred to the at least one remote site. At the remote site the second FFT is inverted to restore the data from the received transfer frequency. The restored data is then zero-padded again to fill the first FFT. The first FFT is then used to transform the zero-padded restored data to provide a data set of points with the target ratio of pixel spacing to resolution.

Non-statistical method for compressing and decompressing complex SAR data

A system for efficiently and reliably communicating over a high-speed asymmetric communications link. The system includes a first mechanism for connecting a first device to a second device via a channel. A second mechanism delivers data packets over the channel from the first device to the second device. Each packet is associated with a window of packets. A third mechanism selectively employs the second mechanism to re-send data packets not received by the second device after each window of packets. The window of packets is sized in accordance with the bandwidth of the communications link between the first device and the second device, and the round trip delay time. In a specific embodiment, the first mechanism (includes Transmission Control Protocol/Internet Protocol (TCP/IP) functionality on the first device and the second device for establishing a first TCP/IP link from the second device to the first device. The first mechanism also includes Universal Datagram Protocol (UDP) functionality on the first device and the second device for transferring UDP packets from the first device to the second device. The third mechanism sends acknowledgement messages from the second device to the first device specifying the packets not received by the second device. The system further includes a fourth mechanism for selectively disabling the second mechanism when first device does not receive an acknowledgement message after a predetermined time interval. The predetermined time interval is a function of a window timeout variable. The predetermined function is (M)&times;(window timeout), where M is approximately 2. The window timeout is greater than N multiplied by a number of packets included in the window of packets divided by the data rate of the communications link between the first device and the second device, here N is an integer greater than 1. N is between 3 and 10.

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Los Angeles, CA, United States of America

Jon H Sherman