National Instruments PCI-4452 - Manual (Page 69)

Chapter 6 Theory of Analog Operation
© National Instruments Corporation 6-11 PCI-4451/4452 User Manual
of eight times the sample rate, as shown in Figure 6-5c. Still, images remain
and they must be filtered out. Each output channel of the PCI-4451 has
discrete-time (switched-capacitor) and continuous-time analog filters that
remove the high-frequency images, as shown in Figure 6-5d.
Figure 6-5. Signal Spectra in the DAC
F
s
8 F
s
16 F
s
Baseband Signal Images
a. Spectrum of Sampled Signal
b. Spectrum of Signal After Digital Filter
Frequency
Amplitude
F
s
8 F
s
16 F
s
Baseband Signal Images After the Digital Filter
Frequency
Amplitude
Amplitude
c. Spectrum of Signal After DAC
F
s
8 F
s
16 F
s
Baseband Signal Images After the DAC
Frequency
Amplitude
d. Spectrum of Signal After Analog Filters
F
s
8 F
s
16 F
s
Baseband Signal
Frequency
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