4.2.2. DAC Interpolation
To generate output signals efficiently a special DAC8580 (6) device was selected for its
integrated interpolation filter, which is especially suitable for the multichannel
transceiver system because the interpolation function allows an accurate waveform to be
reconstructed from a small number of stored samples. The DAC8580 can oversample
the signal by 2, 4 8 or 16 times. This function is implemented by a finite impulse
response (FIR) digital interpolation filter with linear phase. It has a two-frame delay
independent of the oversampling rate. The hardware implementation uses feedback,
therefore it is implemented equivalent to an infinite impulse response (IIR) filter. The Z
transform of the filter is shown in Equation 1. Its low-pass frequency response has
sinx/x envelope to the third power.