--- a/scripts/signal/fftconv.m
+++ b/scripts/signal/fftconv.m
@@ -17,15 +17,16 @@
 ## Software Foundation, 59 Temple Place - Suite 330, Boston, MA
 ## 02111-1307, USA.
 
-## usage: fftconv (a, b [, N])
-##
-## c = fftconv (a, b) returns the convolution of the vectors a and b,
-## a vector with length equal to length (a) + length (b) - 1.
-## If a and b are the coefficient vectors of two polynomials, c is
-## the coefficient vector of the product polynomial.
-##
-## The computation uses the FFT by calling fftfilt.  If the optional
-## argument N is specified, an N-point FFT is used.
+## -*- texinfo -*-
+## @deftypefn {Function File} {} fftconv (@var{a}, @var{b}, @var{n})
+## Return the convolution of the vectors @var{a} and @var{b}, as a vector
+## with length equal to the @code{length (a) + length (b) - 1}.  If @var{a}
+## and @var{b} are the coefficient vectors of two polynomials, the returned
+## value is the coefficient vector of the product polynomial.
+## 
+## The computation uses the FFT by calling the function @code{fftfilt}.  If
+## the optional argument @var{n} is specified, an N-point FFT is used.
+## @end deftypefn
 
 ## Author: KH <Kurt.Hornik@ci.tuwien.ac.at>
 ## Created: 3 September 1994