Dspf_Sp_Icfftr2_Dif - Texas Instruments TMS320C67 DSP Series Programmer's Reference Manual

DSPF_sp_icfftr2_dif

Function
Arguments
Description
Single-precision inverse, complex, radix-2,
decimation-in-frequency FFT
void DSPF_sp_icfftr2_dif (float* x, float* w, short n)
x Input and output sequences (dim-n) (input/output) x has n
complex numbers (2*n SP values). The real and imaginary
values are interleaved in memory. The input is in bit-reversed
order nad output is in normal order.
w FFT coefficients (dim-n/2) (input) w has n/2 complex
numbers (n SP values). FFT coeficients must be in
bit-reversed order. The real and imaginary values are
interleaved in memory.
n FFT size (input).
This routine is used to compute the inverse, complex, radix-2, decimation-in-
frequency Fast Fourier Transform of a single-precision complex sequence of
size n, and a power of 2. The routine requires bit-reversed input and bit-re-
versed coefficents (twiddle factors) and produces results that are in normal or-
der.
Final scaling by 1/N is not done in this function.
How To Use
void main(void)
{
gen_w_r2(w, N); // Generate coefficient table
bit_rev(w, N>>1); // Bit-reverse coefficient table
DSPF_sp_cfftr2_dit(x, w, N);
DSPF_sp_icfftr2_dif(x, w, N);
divide(x, N); // scale inverse FFT output
}
// radix-2 DIT forward FFT
// input in normal order, output in
// order bit-reversed
// coefficient table in bit-reversed
// order
// Inverse radix 2 FFT
// input in bit-reversed order,
// order output in normal
// coefficient table in bit-reversed
// order
// result is the same as original
// input
DSPLIB Reference
DSPF_sp_icfftr2_dif
4-33