ad80164absvz Analog Devices, Inc., ad80164absvz Datasheet - Page 33

• Manufacturer Part Number: ad80164absvz
• Description: Dual, 12-/14-/16-bit,1 Gsps Digital-to-analog Converters
• Manufacturer: Analog Devices, Inc.

Figure 64. Interpolation/Modulation Combination of −1f
Figure 66. Interpolation/Modulation Combination of 2f
Figure 65. Interpolation/Modulation Combination of f
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0
0
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f
f
f
OUT
OUT
OUT
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(× Input Data Rate)
(× Input Data Rate)
(× Input Data Rate)
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DAC
DAC
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DAC
/8 Filter
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Rev. 0 Page 33 of 68
Shifted mode filter responses allow the pass band to be centered
around ±0.5 f
to the shifted mode response does not modulate the signal.
Instead, the pass band is simply shifted. For example, picture
the response shown in Figure 67 and assume the signal in-band
is a complex signal over the bandwidth 3.2 f
the shifted mode filter response is then selected, the pass band
becomes centered at 3.5 f
the same place in the spectrum. The shifted mode capability
allows the filter pass band to be placed anywhere in the DAC
Nyquist bandwidth.
The AD9776A/AD9778A/ AD9779A are dual DACs with
internal complex modulators built into the interpolating filter
response. In dual channel mode, the devices expect the real and
the imaginary components of a complex signal at Digital Input
Port 1 and Digital Input Port 2 (I and Q, respectively). The DAC
outputs then represent the real and imaginary components of
the input signal, modulated by the complex carrier (f
f
With Register 2, Bit 6 set, the device accepts interleaved data
on Port 1 in the I, Q, I, Q . . . sequence. Note that in interleaved
mode, the channel data rate at the beginning of the I and the Q
data paths is now half the input data rate because of the inter-
leaving. The maximum input data rate is still subject to the
maximum specification of the device. This limits the synthesis
bandwidth available at the input in interleaved mode.
With Register 0x02, Bit 5 (real mode) set, the Q channel and
the internal I and Q digital modulation are turned off. The
output spectrum at the I DAC then represents the signal at
Digital Input Port 1, interpolated by 1×, 2×, 4×, or 8×.
The general recommendation is that if the desired signal is
within ±0.4 × f
this, the shifted filter mode should be used. In any situation, the
total bandwidth of the signal should be less than 0.8 × f
DAC
/4, or f
Figure 67. Interpolation/Modulation Combination of 3f
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10
0
–4
DAC
DATA
/8).
DATA
–3
, ±1.5 f
, use the nonshifted filter mode. Outside of
AD9776A/AD9778A/AD9779A
–2
DATA
f
DATA
OUT
, ±2.5 f
–1
(× Input Data Rate)
. However, the signal remains at
0
DATA
, and ±3.5 f
1
DATA
2
DATA
to 3.3 f
DAC
. Switching
3
DAC
/8 Filter
DATA
DATA
/2,
4
. If
.