Rainbow-electronics MAX1195 Manual de usuario descargar pdf (Pagina 18)

MAX1195

quadrature outputs, a local oscillator followed by sub-

sequent upconversion can generate the QAM signal.

The result is an in-phase (I) and a quadrature (Q) carri-

er component, where the Q component is 90° phase

shifted with respect to the in-phase component. At the

receiver, the QAM signal is divided down into its I and

Q components, essentially representing the modulation

process reversed. Figure 10 displays the demodulation

process performed in the analog domain, using the

dual matched 3V, 8-bit ADC MAX1195 and the

MAX2451 quadrature demodulator to recover and digi-

tize the I and Q baseband signals. Before being digi-

tized by the MAX1195, the mixed-down signal compo-

nents may be filtered by matched analog filters, such

as Nyquist or pulse-shaping filters which remove

unwanted images from the mixing process, thereby

enhancing the overall signal-to-noise (SNR) perfor-

mance and minimizing intersymbol interference.

Dual, 8-Bit, 40Msps, 3V, Low-Power ADC with

Internal Reference and Parallel Outputs

18 ______________________________________________________________________________________

1/4 MAX4252

MAX6066

1/4 MAX4252

1.47kΩ

21.5kΩ

47kΩ

3.3V

REFOUT

REFP

REFIN

1µF

10µF

MAX1195

N = 1

REFN

29N.C.

N.C.

COM

REFOUT

NOTE: ONE FRONT-END REFERENCE CIRCUIT DESIGN MAY BE USED WITH UP TO 32 ADCs.

REFP

REFIN

MAX1195

N = 32

REFN

COM

2.0V AT 8mA

0.1µF

MAX4254 POWER SUPPLY

BYPASSING. PLACE CAPACITOR

AS CLOSE AS POSSIBLE TO

THE OP AMP.

3.3V

1.47kΩ

47kΩ

3.3V

1.5V

10µF

1.5V AT 0mA

1.47kΩ

47kΩ

3.3V

10µF

0.1µF0.1µF0.1µF

0.1µF

2.2µF

10V

0.1µF0.1µF

1.0V AT -8mA

330µF

2.0V

1.0V

Figure 9. External Unbuffered Reference Drive with MAX4252 and MAX6066

1 2 ... 13 14 15 16 17 18 19 20 21 22

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Rainbow-electronics MAX1195 Manual de usuario Pagina 18

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