Datasheet
AD9786
Rev. B | Page 36 of 56
Table 33. Dual-Channel Complex Modulation
MODDUAL CHANNEL MOD[1] MOD[0] Mode
0 0 0 0 Real output, no modulation
0 0 0 1 Real output, modulation by f
DAC
/2
0 0 1 0 Real output, modulation f
DAC
/4
0 0 1 1 Real output, modulation f
DAC
/8
0 1 0 0 Image output, no modulation
0 1 0 1 Image output, modulation by f
DAC
/2
0 1 1 0 Image output, modulation by f
DAC
/4
0 1 1 1 Image output, modulation by f
DAC
/8
In dual-channel mode, the two channels can be modulated by
a complex signal, with either the real or imaginary modulation
result directed to the DAC. Assume initially, as in Figure 63,
that the complex modulating signal is defined for a positive
frequency only. This causes the output spectrum to be trans-
lated in frequency by the modulation factor only. No additional
sidebands are created as a result of the modulation process;
therefore, the bandwidth to the first image from the baseband
bandwidth is the same as the output of the interpolation filters.
Furthermore, pass bands do not overlap or touch. The sinc
shaping at the corners of the modulated signal band is tabulated
in Table 34. Figure 64, Figure 65, and Figure 66 show the effects
of complex modulation with varying interpolation rates.
Table 34. Complex Modulated Pass-Band Edges Sinc Shaping
(Lower/Upper)
Interpolation
Modulation None ×2 ×4 ×8
None 0 0 0 0
–2.8241 –0.6708 –0.1657 –0.0413
f
DAC
/2 –0.0701 –1.1932 –2.3248 –3.0590
–22.5378 –9.1824 –6.1190 –4.9337
f
DAC
/4 –0.4680 –0.0175 –0.2921 –0.5974
–6.0630 –3.3447 –1.9096 –1.3607
f
DAC
/8 –1.3723 –0.1160 –0.0044 –0.0727
–4.9592 –1.7195 –0.7866 –0.4614
–
f
DAC
–7
f
DAC
/8
–3
f
DAC
/4
–5
f
DAC
/8
–
f
DAC
/2
–3
f
DAC
/8
–
f
DAC
/4
–
f
DAC
/8
0
f
DAC
/8
f
DAC
/4
3f
DAC
/8
f
DAC
/2
5f
DAC
/8
3f
DAC
/4
7f
DAC
/8
f
DAC
FILTERED INTERPOLATION IMAGES
f
S
/8 MODULATION
NO NEGATIVE
SIDEBAND
–
f
DAC
–7
f
DAC
/8
–3
f
DAC
/4
–5
f
DAC
/8
–
f
DAC
/2
–3
f
DAC
/8
–
f
DAC
/4
–
f
DAC
/8
0
f
DAC
/8
f
DAC
/4
3f
DAC
/8
f
DAC
/2
5f
DAC
/8
3f
DAC
/4
7f
DAC
/8
f
DAC
03152-063
Figure 63. Complex Modulation