RM0020 datasheet(13/69 Pages) STMICROELECTRONICS

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RM0020

Function API

13/69

Function API

6.1

Bit reversal permutation for 16-bit data

Function call:

void bitrev_table_16bit(unsigned int n, short *inout_buffer,

unsigned short *seed_table);

Arguments:

Description:

Implements fast bit reversal permutation on 16-bit complex data using seed table as

described in David M.W.Evans, An Improved Digit-Reversal Permutation Algorithm for

the Fast Fourier and Hartley Transforms IEEE Transactions on Acoustics, Speech,

and Signal Processing, Vol. Assp-35, No. 8, August 1987.

Performance: See Section 7.

Table 1.

bitrev_table_16bit arguments

nin

number of groups:

for radix-2 bit reverse permutation:

n = 8 for 64 and 128-point FFT

n = 16 for 256 and 512-point FFT

n = 32 for 1024 and 2048 point FFT

n = 64 for 4096 point FFT

for radix-4 2-bit reverse permutation:

n = 4 for 64-point FFT

n = 16 for 256 and 1024-point FFT

n = 64 for 4096 point FFT

inout_buffer

in/out

pointer to the input/output vector of length 2*N, vector must be

word aligned

memory layout:

x_Re(0) x_Im(0) x_Re(1) x_Im(1) ... x_Re(N-1) x_Im(N-1)

(Re - real part, Im - imaginary part)

seed_table

pointer to the seed table, use one of the predefined tables:

seed_radix2_16bit_64

seed_radix2_16bit_128

seed_radix2_16bit_256

seed_radix2_16bit_512

seed_radix2_16bit_1024

seed_radix2_16bit_2048

seed_radix2_16bit_4096

seed_radix4_16bit_64

seed_radix4_16bit_256

seed_radix4_16bit_1024

seed_radix4_16bit_4096

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