AD9786BSVRL datasheet(41/56 Pages) AD

41 / 56 page

AD9786

Rev. B | Page 41 of 56

1200

100

200

400

600

800

1000

–4

–1

–2

–3

Figure 76. Phase Response of Hilbert Transform

Table 37. Dual Channel Complex Modulation Sideband Selection

Sideband

Mode

Upper IF sideband rejected

Lower IF sideband rejected

AD9786

Im()

Re()

Figure 77. AD9786 Driving Quadrature Modulator

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.

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.

0.5

–0.5

–0.4

–0.3

–0.2

–0.1

0.1

0.2

0.3

0.4

–150

–50

–100

Figure 78. Upper IF Sideband Rejected

0.5

–0.5

–0.4

–0.3

–0.2

–0.1

0.1

0.2

0.3

0.4

–150

–50

–100

Figure 79. Lower IF Sideband Rejected

BASEBAND

SIDEBAND = 1

SIDEBAND = 0

Figure 80. IF Quadrature Modulation of Real and Complex Baseband Signals

AD9786BSVRL Datasheet(PDF) 41 Page - Analog Devices

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