Allpass vs. unit-norm constraints in contrast-based blind deconvolution

Many contrast-based independent component analysis (ICA) algorithms can be directly applied to single-channel blind deconvolution tasks without modification. For prewhitened signals, however, an allpass constraint on the filter impulse response is more appropriate than a unit-norm constraint. We show how a finite-impulse-response filter can be adapted to maximize or minimize an arbitrary contrast function while approximately maintaining an allpass characteristic in a self-stabilizing fashion. Both online time domain and block-based frequency domain algorithms are described. Simulations verify the superior performance behaviors of the new algorithms over those of standard ICA algorithms in prewhitened blind deconvolution tasks.