Ifft - Analog Devices VISUALDSP++ 3.5 Manual

ifft

N point inverse FFT
Synopsis
#include <filter.h>
void ifft_fr16(in[], t[], out[], w[], wst, n, block_exponent,
const complex_fract16 in[];
complex_fract16 t[];
complex_fract16 out[];
const complex_fract16 w[];
int wst;
int n;
int *block_exponent;
int scale method;
Description
This function transforms the frequency domain complex input signal
sequence to the time domain by using the radix-2 Fast Fourier Transform.
The size of the input array
working buffer
The function does not impose any special memory alignment require-
ments on the arrays. However, benefits in run-time performance will be
realized if the output array is allocated on an address boundary that is
multiple of twice the FFT size. If the input data can be overwritten, then
optimum memory usage can be achieved by specifying the input array as
the output array.
The twiddle table is passed in the argument
twiddle coefficients. The function
n/2
initialize the array. If the twiddle table contains more coefficients than
needed for a particular call on
set appropriately; otherwise it should be 1.
VisualDSP++ 3.5 C/C++ Compiler and Library Manual
for ADSP-219x DSPs
scale_method)
, the output array
in
is , where represents the number of points in the FFT.
t n n
ifft_fr16
DSP Run-Time Library
/* input sequence
/* temporary working buffer
/* output sequence
/* twiddle sequence
/* twiddle factor stride
/* number of FFT points
/* block exponent of output data */
/* scaling method desired 0-none,
1-static, 2-dynamic
, and the temporary
out
, which must contain at least
w
twidfftrad2_fr16
, then the stride factor has to be
*/
*/
*/
*/
*/
*/
*/
may be used to
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