Datasheet
delayed in in in
0
delayed in in in
0
2 2 1
I (t) I cos Q sin I t
16 16 16
2 2 1
Q (t) Q cos I sin Q t
16 16 16
æ ö
p p
æ ö æ ö
= + = +
ç ÷
ç ÷ ç ÷
è ø è ø
è ø
æ ö
p p
æ ö æ ö
= - = +
ç ÷
ç ÷ ç ÷
è ø è ø
è ø
f
f
1
T
16
1
T
16
Fin 1X Clock
1X Clock
Phase 0°
Fin 16X Clock
1X Clock
Phase 22.5°
1X Clock
Phase 45°
1X Clock
Phase 90°
Quadrature
clocks
1X Clock
Phase 337.5º
16-to-8 Cross Point Switch
1X Clock
Phase 0º
1X Clock
Phase 22.5º
1X Clock
Phase 315º
1X Clock
Phase 292.5º
Mixer 1
1X Clock
Mixer 2
1X Clock
Mixer 3
1X Clock
Mixer 6
1X Clock
Mixer 7
1X Clock
Mixer 8
1X Clock
Fin 16X Clock
SPI
D Q
Fin 1X Clock
INV
16 Phase Generator
Fin 1X Clock
AFE5808A
www.ti.com
SLOS729B –OCTOBER 2011–REVISED APRIL 2012
Figure 72.
Figure 73. 1x and 16x CW Clock Timing
8 × ƒ
cw
and 4 × ƒ
cw
Modes
8 × ƒ
cw
and 4 × ƒ
cw
modes are alternative modes when higher frequency clock solution (i.e. 16 × ƒ
cw
clock) is not
available in system. The block diagram of these two modes is shown below.
Good phase accuracy and matching are also maintained. Quadature clock generator is used to create in-phase
and quadrature clocks with exact 90° phase difference. The only difference between 8 × ƒ
cw
and 4 × ƒ
cw
modes
is the accessibility of the 3rd and 5th harmonic suppression filter. In the 8 × ƒ
cw
mode, the suppression filter can
be supported. In both modes, phase delay resolution is achieved by weighting the in-phase and quadrature
paths correspondingly. For example, if a delay of or 22.5° is targeted, the weighting coefficients should
follow the below equations, assuming I
in
and Q
in
are sin(ω
0
t) and cos(ω
0
t) respectively:
(4)
Therefore, after I/Q mixers, phase delay in the received signals is compensated. The mixers’ outputs from all
channels are aligned and added linearly to improve the signal to noise ratio. It is preferred to have the 4 × ƒ
cw
or
8 × ƒ
cw
and 1 × ƒ
cw
clocks aligned both at the rising edge.
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