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| DSP_fft16x16t |
/* y0i = x0i + x2i + x1i + | x3i | = | xh1 + xh21 | */ |
/* y1r = x0r − x2r + (x1i − | x3i) | = | xl0 + xl21 | */ |
/* y1i = x0i − x2i − (x1r − | x3r) | = | xl1 − xl20 | */ |
/* y2r = x0r + x2r − (x1r + | x3r) | = | xh0 − xh20 | */ |
/* y2i = x0i + x2i − (x1i + | x3i | = | xh1 − xh21 | */ |
/* y3r = x0r − x2r − (x1i − | x3i) | = | xl0 − xl21 | */ |
/* y3i = x0i − x2i + (x1r − | x3r) | = | xl1 + xl20 | */ |
/* −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−*/
y0r | = xh0_0 + | xh20_0; y0i | = xh1_0 | + xh21_0; | |||
y4r | = xh0_1 + | xh20_1; y4i | = xh1_1 | + xh21_1; | |||
xt0_0 = xh0_0 − | xh20_0; yt0_0 | = xh1_0 | − xh21_0; | ||||
xt0_1 = xh0_1 − | xh20_1; yt0_1 | = xh1_1 | − xh21_1; | ||||
xt1_0 = xl0_0 | + | xl21_0; yt2_0 | =xl1_0 |
| + xl20_0; | ||
xt2_0 = xl0_0 | − | xl21_0; yt1_0 | =xl1_0 |
| − xl20_0; | ||
xt1_1 | = xl0_1 | + | xl21_1; yt2_1 |
| =xl1_1 |
| + xl20_1; |
xt2_1 | = xl0_1 | − | xl21_1; yt1_1 |
| =xl1_1 |
| − xl20_1; |
/*−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−*/ /* Store out first output, of the four outputs of a radix4 */
/* | butterfly. Since two such | radix4 butterflies are per− | */ |
/* | formed in parallel, there | are 2 such 1st outputs. | */ |
/*−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−*/
x2[0] | = | y0r; | x2[1] | = | y0i; |
x2[2] | = | y4r; | x2[3] | = | y4i; |
/*−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−*/
/* Perform twiddle factor multiplies of three terms,top | */ |
/* term does not have any multiplies. Note the twiddle | */ |
/* factors for a normal FFT are C + j (−S). Since the | */ |
/* factors that are stored are C + j S, this is | */ |
/* corrected for in the multiplies. | */ |
/* | */ |
/* Y1 = (xt1 + jyt1) (c + js) = (xc + ys) + (yc −xs) | */ |
/* Perform the multiplies using 16 by 32 multiply macro | */ |
/* defined. This treats the twiddle factor as 16 bits | */ |
/* and incoming data as 32 bits. | */ |
/*−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−*/ x2[h2 ] = (si10 * yt1_0 + co10 * xt1_0) >> 15;
C64x+ DSPLIB Reference |
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