Chapter 3 85
Theory of Operation
Digital Predistortion
Digital Predistortion
The predistortion function compensates for the variation in the magnitude of the
output response as a function of frequency. This variation is the result of the sin x/x
(sinc) roll-off of the internal DAC and the frequency response of the reconstruction
filter. The correction method uses filters to level the amplitude response and to
create a linear phase response at the front panel of the AWG. This process attenuates
the signal as a function of frequency, but cannot increase the signal above the
maximum output voltage. Therefore, it is necessary to attenuate the lower frequency
signals. This results in a reduced output voltage and dynamic range at all
frequencies, but with uniform response across the full frequency range.
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