
DAC5674
SLWS148A SEPTEMBER 2003 REVISED OCTOBER 2005
www.ti.com
15
Low-Pass/Low-Pass 4
y Interpolation Filter Operation
Figure 16 shows the low-pass/low-pass interpolation operation where the 4
× FIR filter is implemented as a
cascade of two 2
× interpolation filters with the input signal coming from a digital signal source such as an FPGA
or digital upconverter (DUC). Users can place their IF signal at a maximum of 0.4 times the FIR filter input (i.e.,
DAC5674 input) data rate. For a 100-MSPS data rate, this would translate into a pass band extending to 40
MHz.
Fdata
=
Fdac
Input Spectrum
Output of DUC
1st 2x
interpolation
filter
Spectrum after
2x interpolation
2nd 2x
interpolation
filter
Spectrum after
4x interpolation
80 dB of
attenuation
2nd LPF removes
interpolation images
Figure 16. Low-Pass/Low-Pass 4
y Interpolation Filter Operation