ST70235A datasheet(10/28 Pages) STMICROELECTRONICS

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ST70235A

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Figure 3 : DSP Front-End Receive

This stream is still affected by carrier specific

channel distortion resulting in an attenuation of

the signal amplitude and a rotation of the signal

phase. To compensate, a Frequency domain

equalizer (FEQ) and a Rotor (phase shifter) are

implemented. The frequency domain equalization

performs an operation on the received vector in

order to match it with the associated point in the

constellation. The coefficient used to perform the

equalization are floating point, and may be

updated by hardware or software, using a

mechanism of active and inactive table to avoid

DMT synchro problems.In the transmit path, the

IFFT reverses the DMT symbol from frequency

domain to time domain.

The IFFT block is preceded by Fine Tune Gain

(FTG)

and

Rotor

stages,

allowing

for

compensation of the possible frequency mismatch

between the master clock frequency and the

transmitter clock frequency (which may be locked

to another reference).

The Inverse Fast Fourier Transform process is

used to transform from frequency domain to time

domain (transmit path). 256 positive frequencies

are processed, giving 512 samples in the time

domain.

Figure 4 : DSP Front-End Transmit

Figure 5 : DMT Modem (Rx & Tx)

From

Analog

Front-end

SELECT

AFE

I/F

DEC

TEC

BYPASS

To DMT

Modem

From

DMT

Modem

FILTERING

CLIPPING

AFE

I/F

To Analog

Front End

DELAY

EQUALIZER

OUT

SELECT

INTER-

POLATOR

To/From

DSP FE

FFT

IFFT

FEQ

FTG

MAPPER

DEMAPPER

ROTOR

To/From

TREILLIS

CODING

DECODING

MONITOR

FEQ COEFFICIENTS

FEQ Update

Monitor Indications

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