Multirate Digital Signal Processing, Oversampling of Analog-to-Digital Conversion, and Undersampling of Bandpass Signals - Digital Signal Processing: Fundamentals and Applications - page 610

1 0.8

0.6

0.5 0.4

0.2

0 0

0.9 0.95 1 1.05 1.1

x 10 5

0 2000 4000 6000 8000

Frequency (Hz) 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 12.45B

Sampled AM signal and spectrum for f c ¼ 100 kHz.

for (j ¼ 0;j<M;j þþ )
{

for(i ¼ 66; i>0; i--) // Update input buffer
{ x[i] ¼ x[i-1]; }
x[0] ¼ lc; // Load new sample
sum

0.0;
for(i

¼

¼ 0;i<67;i þþ ) // FIR filtering

{ sum ¼ sum þ x[i]*b[i]; }

if (j ¼¼ 0)

{ y[0] ¼ sum; } // Update DAC with processed sample (decimation)

}
// End of the DSP algorithm
lcnew

y[0]; /* Send to DAC */
rcnew ¼ y[0];
AIC23_data.channel[LEFT] ¼ (short) lcnew;
AIC23_data.channel[RIGHT] ¼ (short) rcnew;
output_sample(AIC23_data.combo);

¼

}