RF-DAC Inverse Sinc Filter - 2.6 English

Zynq UltraScale+ RFSoC RF Data Converter v2.6 Gen 1/2/3/DFE LogiCORE IP Product Guide (PG269)

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2.6 English

The analog output response of the RF-DAC follows a characteristic sinx/x, or sinc shape. For applications that require flat-output response over a wide bandwidth, an inverse sinc filter is available to achieve this. The inverse sinc filter is an 11-tap FIR, which provides a flat-response with less than ±0.05 dB of ripple up to 89% of Nyquist, or ± 0.033 dB of ripple up to 80% of Nyquist. The following figure shows the inverse sinc performance.

Figure 1. Inverse Sinc Frequency Response

The line in blue represents the frequency response of the filter itself. As can be seen, it increases with frequency to compensate for the sinc response of the output, as shown by the red line. The composite output response is given by the yellow trace, and shows a flat pass-band up to 89% of Nyquist. The following figure shows the detail of the corrected response, with ripple specification levels highlighted in red.

Figure 2. Inverse Sinc Detail