AFE5808A datasheet(43/66 Pages) TI1

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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

1X Clock

Phase 0°

Fin 16X Clock

1X Clock

Phase 22.5°

1X Clock

Phase 45°

1X Clock

Phase 90°

Quadrature

clocks

delayed

(t)

I cos

Q sin

(t)

Q cos

I sin

AFE5808A

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SLOS729B – OCTOBER 2011 – REVISED APRIL 2012

Figure 72.

Figure 73. 1x and 16x CW Clock Timing

8 × ƒcw and 4 × ƒcw Modes

8 × ƒcw and 4 × ƒcw modes are alternative modes when higher frequency clock solution (i.e. 16 × ƒcw 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 × ƒcw and 4 × ƒcw modes

is the accessibility of the 3rd and 5th harmonic suppression filter. In the 8 × ƒcw 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 Iin and Qin are sin(ω0t) and cos(ω0t) 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 × ƒcw or

8 × ƒcw and 1 × ƒcw clocks aligned both at the rising edge.

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