SAR/GPR Matched Filter Processing for UXO Discrimination
Abstract
In order to achieve focused SAR images it is necessary to have accurate knowledge of the radar antenna position during its motion over the synthetic aperture. This position information is used to ensure proper focusing of the SAR image by phase compensating the data collected over the entire SAR path. This process is known as motion compensation and requires precise measurement of the position of the phase center of the GPR antenna. The positioning measurement system utilized on this project used electronic repeaters that act as reference targets within the SAR field of view. The repeater-based measurement technique works as follows. Each repeater receives the radar signal, alters it by imposing a pseudo-Doppler modulation onto the signal, and then transmits this modulated signal back to the radar. The repeater signals are, thus, embedded in the normal radar data stream; no special radar modifications are required to receive the repeater signals. A different Doppler frequency is used for each individual repeater allowing each repeater to be uniquely identified. After Doppler processing, the responses from the repeaters stand out above the background clutter with high signal quality (i.e., high signal to clutter ratio) because the repeater signals have been Doppler shifted away from the zero-Doppler background clutter. Due to the high quality of the repeater signals, with post processing of the data, the range between each repeater and the SAR antenna is precisely determined. A tri-lateration algorithm is then used on three repeater ranges to accurately locate the SAR antenna's 3D position. Only the precise relative locations of the repeaters with respect to each other are needed in order to form a sharply focused SAR image; absolute geo-location of the repeaters also allows the focused SAR image to be accurately geo-referenced as well.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 21, 2001
- Accession Number
- ADA480904