PROCESS F2T


Documentation Date:  18 May 2000

Process F2T transforms frequency domain data to the time domain.
Process T2F must have been used to create the frequency domain.  The
frequency domain data may be in rectangular or polar coordinates
(parameter COORDS in process T2F).
 
A quadrature trace (or 90 degree phase shifted trace) may be obtained
through a Hilbert transform and parameter TYPE HILBERT.

An analytic trace may be formed by using parameter TYPE ANALYTIC.  In
this case, the trace samples are an interleaving of the input trace 
and the Hilbert transformed trace, so that there are twice as many
output samples as input.  The instantaneous amplitude may be formed
by using process GAINS TYPE 7 (modulus of a complex trace).

PARAMETER DICTIONARY
--------- ----------
TYPE - The type of data output by process F2T.
     = TIME, The real time domain.
     = COMPLEX, The complex time domain.
     = HILBERT, The real time domain with Hilbert transform 
                (phase shifted by 90 degrees).
     = ANALYTIC, The analytic time domain trace. (c(t) = a(t)+ib(t),
                 where c(t) is a complex trace of a(t) the input
                 trace and b(t) is the phase shifted trace).
     Default = TIME.

Written and copyrighted (c) by:
Paul Henkart, Scripps Institution of Oceanography, 21 January 1984
all rights are reserved by the author.  Permission to copy or reproduce this
subroutine, by computer or other means, may be obtained only from the author.