Multirate Digital Signal Processing, Oversampling of Analog-to-Digital Conversion, and Undersampling of Bandpass Signals - Digital Signal Processing: Fundamentals and Applications - page 609

2 1

1

0 0.5

-1

-2 0

0 0.005 0.01 0.9 0.95 1 1.05 1.1

x 10 5

Time (s ec . ) Frequency (Hz)

2 1

1.5

1 0.5

0.5

0 0

0 0.005 0.01 0 2000 4000 6000 8000

Time (s ec . ) Frequency (Hz)

FIGURE 12.45A

Sampled AM signal and spectrum for f c ¼ 96 kHz.

Program 12.9. Downsampling implementation (anti-aliasing filter has 67 coefficients that are stored in
an array b[67]).

int M ¼ 2;
float x[67];
float y[1] ¼ {0.0};
interrupt void c_int11()
{

float lc; /*Left channel input */
float rc; /*Right channel input */
float lcnew; /*Left channel output */
float rcnew; /*Right channel output */
int i,j;
float sum;
// Left channel and right channel inputs
AIC23_data.combo

¼ input_sample();

lc ¼ (float) (AIC23_data.channel[LEFT]);

(float) (AIC23_data.channel[RIGHT]);
// Insert DSP algorithm below

rc ¼