MC92314 View Datasheet(PDF) - Motorola => Freescale

Part Name

Description

Manufacturer

MC92314

DVB-T Single Chip Demodulator Application Note

Motorola => Freescale 

Freescale Semiconductor, Inc.

Device Description

Clock

VCXO

CLK Loop

Filter & DAC

Time Sync

(Coarse &

Fine)

From ADC

Received Data

I/Q Demodulator

& Derotator

FFT Block

Channel Data RAM

Extracted

Pilots

Data

Formatter

Control

G1, G2

Data

Symbol

Deinterleav-

ing & De-

mapping

tion AGC

AGC-DAC

AFC

AGC

I2C & Par-

allel

Interface

TPS & Frame Syn-

chronisation

Channel Es-

timation &

Correction

Channel

State

Estimation

rma Figure 3-3. OFDM Demodulator Part of the MC92314

fo 3.2.2.1 I/Q-Demodulator

In In this first stage the complex samples are reconstructed from the (real valued) input stream by

y means of a discrete Hilbert transformer. The input stream is fed into the Hilbert transformer and

r delayed appropriately to calculate the real and imaginary parts of the signal.

ina 3.2.2.2 Derotator

Carrier frequency offsets resulting from local oscillator offsets in the tuner are removed digitally

lim by means of a NCO and a phase accumulator, that are controlled by the Automatic Frequency

Control (AFC). During the acquisition phase (when locking onto a DVB-T transmission) the AFC

re circuit sweeps permanently through the available range until the correct frequency offset has

P been detected. During the tracking phase the control signal for the phase increment is derived

from the pilot carriers in the frequency domain.

3.2.2.3 Time Synchronisation

The Time Synchronisation (separated in the coarse synchronisation valid during the acquisition

phase and the fine synchronisation for tracking purposes) sets the FFT window position for the

real OFDM demodulation and controls the clocking of the whole chip.

In the tracking mode the time synchronisation generates the VCXO control signal using the filter

structure given in Figure 3-4 below. The contribution of the proportional branch and of the

integrator branch can be adjusted separately using the Clock Loop Filter Coefficients (see also

paragraph 4.2.2.1.5).

The gain of the proportional part is set using Bits [7:4] and the gain of the integrator part is

adjusted with Bits [3:0].

Single Chip DVB-T Demodulator - Rev. 1.3 (11/30/98)

For More Information On This Product,

Go to: www.freescale.com

MOTOROLA

3-3

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