AD9786 Analog Devices, AD9786 Datasheet - Page 41

• 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

Table 37. Dual Channel Complex Modulation Sideband Selection
Sideband
0
1
The AD9786 can be configured to drive a quadrature modulator,
as in Figure 77. When two AD9786s are used with one AD9786
producing the real output, the second AD9786 produces the
imaginary output. By configuring the AD9786 as a complex
modulator coupled to a quadrature modulator, IF image
rejection is possible. The quadrature modulator acts as the real
part of a complex modulation, producing a double sideband
spectrum at the local oscillator (LO) frequency with mirror
symmetry about dc.
–1
–2
–3
–4
4
3
2
1
0
100
Figure 77. AD9786 Driving Quadrature Modulator
Figure 76. Phase Response of Hilbert Transform
Q
I
200
Mode
Upper IF sideband rejected
Lower IF sideband rejected
AD9786
AD9786
400
LO
600
Re()
Im()
0
Figure 80. IF Quadrature Modulation of Real and Complex Baseband Signals
90
800
1000
1200
Rev. B | Page 41 of 56
BASEBAND
A baseband double sideband signal modulated to IF increases
IF filter complexity and reduces power efficiency. If the base-
band signal is complex, a single sideband IF modulation can be
used, relaxing IF filter complexity and increasing power
efficiency.
The AD9786 has the ability to place the baseband single side-
band complex signal either above or below the IF frequency.
Figure 78, Figure 79, and Figure 80 illustrate this.
–100
–150
–100
–150
–50
–50
IF
0
–0.5
0
–0.5
–0.4
–0.4
Figure 78. Upper IF Sideband Rejected
Figure 79. Lower IF Sideband Rejected
–0.3
–0.3
–0.2
–0.2
SIDEBAND = 1
SIDEBAND = 0
–0.1
–0.1
0
0
0.1
0.1
0.2
0.2
0.3
0.3
0.4
0.4
AD9786
0.5
0.5