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Function API

RM0020

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Description:

Split function of N-point real to complex frac32 in-place fast Fourier transform (FFT).

Input 32-bit fractional data are stored in y, output 32-bit fractional data are written over

the input data into y. The function gives the first half of the output spectrum.

The calculation of the N/2 item is configurable by constant definition in the function

source file:

.set

N2_REALPART,

#/* 0/1 - real part of N/2

item isn't/is inserted in imaginary part of 0th item, default

value is 0 */

By default the N/2 output item is not calculated.

The output scaling is configurable by constant definition in the function source file:

.set

SCALING

#/* 0 - off, 1 - on */

By default it is turned on. The scaling is performed by dividing input data by 2 before

calculation.

pointer to the wa vector of twiddle factors of length N/4+1, vector

must be double word aligned

memory layout:

wa_Re(0) wa_Im(0) wa_Re(1) wa_Im(1) ... wa_Re(N/4+1)

wa_Im(N/4+1)

Use predefined wa_table_frac32_N arrays.

The wa_table_frac32_N is computed according to this formula:

for k = 0, 1, ... N/4+1

, where i is the imaginary unit

pointer to the wb vector of twiddle factors of length N/4+1, vector

must be double word aligned

memory layout:

wb_Re(0) wb_Im(0) wb_Re(1) wb_Im(1) ... wb_Re(N/4+1)

wb_Im(N/4+1)

Use predefined wb_table_frac32_N arrays.

The wb_table_frac32_N is computed according to this formula:

for k = 0, 1, ... N/4+1

, where i is the imaginary unit

Table 10.

fft_real_split_frac32 arguments (continued)

wa k



--- 1iW

–







------

–

wb k



--- 1iW







------

–

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