National Instruments Car Stereo System 320571-01 用户手册

Computes the inverse fast Hartley transform of
the input sequence FHT {X}.  The inverse
Hartley transform of a function X(f) is defined
as

x(t)  = 

∫

-

∞

∞

 X(f) cas(2

π

ft) df

where cas(x)  =  cos(x) + sin(x).

If Y represents the output sequence X, the VI calculates Y through the discrete implementation of the inverse
Hartley integral:

Y

k

  =  

1

n

 

∑

i=0

n-1

 X

i

  cas 

( )

2

π

 ik

n

 

for  k = 0, 1, 2, … , n-

1

where n is the number of elements in X.

The inverse Hartley transform maps real-valued frequency sequences into real-valued sequences.  You can use it
instead of the inverse Fourier transform to convolve, deconvolve, and correlate signals.  Furthermore, you can derive
the Fourier transform from the Hartley transform.

See the description of the DSP FHT VI for a comparison of the Fourier and Hartley transforms.

FHT {X} is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the
input signal array.

Notes: The number of elements for the input array must be a power of 2.

The operation is performed in place and the input array FHT {X} is overwritten by
the output array X.

The largest inverse FHT that can be computed depends upon the amount of memory in your
DSP board.

X is a DSP Handle Cluster that is identical to FHT {X}, but with the results of inverse FHT {X } already
stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI.  If an error occurs, it is passed out
error out and no other calls are made.

error out contains the error information for this call.