Autofocus Algorithms for Passive Radar

In radar imaging, phase errors result in defocused images. These phase errors are primarily a consequence of inaccuracies in the demodulation time at the reciever due to not precisely knowing the propagation time of radar pulses from transmitter to target to receiver. Autofocus algorithms create an estimate of the phase error function to correct defocussed radar images.

I am currently investigating autofocus solutions that apply to passive radar with multiple transmitters and a single receiver. Traditional autofocus techniques consider only monostatic, active radar situations. The situation I consider adds the complexity of a passive scenario, which results in reduced illumination (in bandwidth) of the target, and multiple transmitters, which causes Fourier imaging data to be scattered on varying rings of many circles, as opposed to a nice arc. Each transmitter will induce a different phase error function, making the problem of focusing an image a real challenge.

To learn more about the Design and Optimization of Passive and Active Imaging Radar project at the University of Illinois at Urbana-Champaign, visit the project website:

http://www.ifp.uiuc.edu/~lanterma/darpa/