FUNCTION wiener_t_fun, r_in, b_out, snr, alpha
; returns the wiener linear transfer function
;
; Author:  Robert Kessel
;          Electro-Optics Technology Section
;          Code 8123
;          Naval Research Laboratory
;          Washington, D.C.  20375-5354
; email:   kessel@ncst.nrl.navy.mil
;
; This code was written for Bill Palya's and Don Walter's
; use at JSU.  However, anyone else who finds it useful
; should feel free to use it, rewrite it, or whatever else,
; save charging any money, goods or services from any other
; person for the code or use thereof.
; 10/20/03

r_in_freq = FFT(r_in)
b_out_freq = FFT(b_out)

t_fun = b_out_freq*CONJ(r_in_freq)/((r_in_freq*CONJ(r_in_freq)) + $
    (alpha/snr)^2)

RETURN, t_fun
END