SARsignal

SARsignal is the coherent microwave radar signal used by synthetic aperture radar (SAR) systems to produce high-resolution images of the surface. In a SAR, the transmitted waveform is typically a wideband, frequency-modulated chirp, which allows fine range resolution; the echoes received from the scene are phase coherent with the transmitted signal, preserving information needed to form a two-dimensional image as the platform moves.

Because the radar platform travels along a flight path, the collection of successive backscatter samples from a moving point creates a synthetic aperture. In processing, the raw data undergo motion compensation, range compression (matched filtering to the transmitted chirp), and azimuth compression (Doppler processing) to produce a focused image with fine azimuth and range resolution. The phase information also enables interferometric and polarimetric techniques.

SAR signals are designed to operate in different microwave bands (for example L, C, X) and can be coded or shaped for various applications. Common variants include polarimetric SAR, which uses multiple polarizations to extract scene scattering properties, and interferometric SAR (InSAR), which compares phase between acquisitions to measure height or deformation.

Applications of SAR signals span earth observation, topographic mapping, monitoring of land cover and forests, oceanography, disaster response, and surveillance. Challenges include speckle noise, geometric distortions such as layover and foreshortening, atmospheric phase delay, and the need for precise satellite or aircraft motion data for accurate processing.