A method is suggested for development of interference-immune adaptive algorithms of digital multichannel signal processing that allows to take into account both mutual correlation of the channel interference readings and their probabilistic characteristics. The method is based on the representation of channel signals transformation by the series expansion using a system of multidimensional orthogonal functions with coefficients optimal in accordance with the method of least squares of process deviations at the processor output from the useful signal. A system of functions implementing the multidimensional nonlinear quantization of channel signals is proposed. The study results for digital broadband signal processing against the interference background in a 20-element antenna array are given.