AD9776-EB datasheet(32/56 Pages) AD

32 / 56 page

AD9776/AD9778/AD9779

Rev. A | Page 32 of 56

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fOUT (× Input Data Rate)

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Figure 59. 8× Interpolation, Low-Pass Response to ±4× Input Data Rate

(Dotted Lines Indicate 1 dB Roll-Off)

With the interpolation filter and modulator combined, the

incoming signal can be placed anywhere within the Nyquist

region of the DAC output sample rate. When the input signal is

complex, this architecture allows modulation of the input signal

to positive or negative Nyquist regions (see Table 17).

The Nyquist regions of up to 4× the input data rate can be seen

in Figure 60.

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Figure 60. Nyquist Zones

Figure 57, Figure 58, and Figure 59 show the low-pass response

of the digital filters with no modulation. By turning on the

modulation feature, the response of the digital filters can be

tuned to anywhere within the DAC bandwidth. As an example,

Figure 61 to Figure 67 show the nonshifted mode filter responses

(refer to Table 17 for shifted/nonshifted mode filter responses).

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Figure 61. Interpolation/Modulation Combination of 4 fDAC/8 Filter

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Figure 62. Interpolation/Modulation Combination of −3 fDAC/8 Filter

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Figure 63. Interpolation/Modulation Combination of −2 fDAC/8 Filter

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Figure 64. Interpolation/Modulation Combination of −1 fDAC/8 Filter

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