A derivation of the normal equation in FIR Wiener filters
Y.-D. Huang, C.-T. Chen · IEEE Transactions on Acoustics Speech and Signal Processing · 1989
In developing the normal equation of the finite-duration impulse-response Wiener filter, the method of taking a gradient of scalar-valued mean-square error to complex tap-weight vector is discussed. A variational method used to attain the normal equation is also included.>