AD9786 Analog Devices, AD9786 Datasheet - Page 33

• Manufacturer Part Number: AD9786
• Manufacturer: Analog Devices

Specifications of AD9786

• Resolution (bits): 16bit
• Dac Update Rate: 500MSPS
• Dac Settling Time: n/a
• Max Pos Supply (v): +3.5V
• Single-supply: No
• Dac Type: Current Out
• Dac Input Format: Par

MODULATION MODES
Table 30. Single-Channel Modulation
MODDUAL
0
0
0
0
0
0
0
0
Either channel of the AD9786 interpolation filter channels can
be routed to the DAC and modulated. In single-channel
operation, the input data can be modulated by a real sinusoid;
the input data and the modulating sinusoid contain both
positive and negative frequency components. A double side-
band output results when modulating two real signals. At the
DAC output, the positive and negative frequency components
add in phase, resulting in constructive signal summation.
As the modulating sinusoidal frequency becomes a larger
fraction of the DAC update rate, f
DAC shapes the modulated signal bandwidth more, and the
first image moves closer.
Because the AD9786 interpolation filter pass band represents a
large portion of the input data Nyquist band, it is possible for
modulated signal bands to touch or overlap images if sufficient
interpolation is not used under certain modulation and
interpolation modes.
Figure 59 shows the effects of f
interpolation. Figure 60 to Figure 62 show the effects of real
modulation under all interpolation modes. The sinc shaping at
the corners of the modulated signal band and the bandwidth to
the first image for those cases whose pass bands do not touch or
overlap are tabulated.
CHANNEL
0
0
0
0
1
1
1
1
DAC
DAC,
/8 modulation when using 8×
the sinc function of the
MOD[1]
0
0
1
1
0
0
1
1
Rev. B | Page 33 of 56
MOD[0]
0
1
0
1
0
1
0
1
Table 31. Synthesis Bandwidth vs. Interpolation Modes
Modulation
None
f
f
f
Table 32. Modulated Pass-Band Edges Sinc Shaping
(Lower/Upper)
Modulation
None
f
f
f
DAC
DAC
DAC
DAC
DAC
DAC
/2
/4
/8
/2
/4
/8
Mode
I channel, no modulation
I channel, modulation by f
I channel, modulation by f
I channel, modulation by f
Q channel, no modulation
Q channel, modulation by f
Q channel, modulation by f
Q channel, modulation by f
None
f
f
Overlap
Overlap
SIN
SIN
None
0
–2.8241
–0.0701
–22.5378
Overlap
Overlap
×2
0
–0.6708
–1.1932
–9.1824
Touching
Overlap
×2
2 f
2 f
Touching
Overlap
Interpolation
Interpolation
DAC
DAC
DAC
SIN
SIN
DAC
DAC
DAC
/2
/4
/8
/2
/4
/8
×4
0
–0.1657
–2.3248
–6.1190
–0.2921
–1.9096
Touching
×4
4 f
4 f
2 f
Touching
SIN
SIN
SIN
AD9786
×8
0
–0.0413
–3.0590
–4.9337
–0.5974
–1.3607
–0.0727
–0.4614
×8
8 f
8 f
4 f
6 f
SIN
SIN
SIN
SIN