We present a new ``second generation"
reconstruction algorithm for irregular sampling, i\@.e\@. for the
problem of
recovering a band-limited function from its non-uniformly sampled
values. The efficient new method is a combination of the adaptive
weights
method which was developed by the two first named authors
and the method of conjugate gradients for the solution of positive
definite linear systems.
The choice of "adaptive weights" can be seen as a simple but very
efficient
method of preconditioning. Further substantial acceleration is
achieved by utilizing the Toeplitz-type structure of the system
matrix. This new algorithm can handle problems of much larger
dimension and condition number than have been
accessible so far. Furthermore, if some gaps between samples are
large, then the algorithm can still be used as a very efficient
extrapolation method across the gaps.
Mathematics Subject Classification (1991): 42A15, 65D05, 65D10, 65F10
Received December 22, 1993