MC92314 View Datasheet(PDF) - Motorola => Freescale

Part Name

Description

Manufacturer

MC92314

DVB-T Single Chip Demodulator Application Note

Motorola => Freescale 

System Overview

Freescale Semiconductor, Inc.

1.4.2 OFDM Block

The OFMD block performs the functions given in the blocks ‘Synchronisation’, ‘Demapping’ and

‘Inner Deinterleaving’ in Figure 1-2. This includes all the necessary synchronisation tasks,

OFDM-related deinterleaving, demapping of the constellation diagram, generation of soft-

decision information and output formatting. This block is designed to work directly with the FFT

block.

Important capabilities are:

• Usable for 8 MHz, 7 MHz and 6 MHz channel bandwidth by adjusting the clock rate.

• C/N performance according to Reference [1-1] Annex A with a degradation margin of 3 dB.

• Supported DVB-T modulation schemes: QPSK, 16-QAM and 64-QAM.

• Automatic lock on all specified guard interval lengths (1/32, 1/16, 1/8, 1/4).

n • Data input: 8 Bit TTL compatible 2’s complement or offset binary.

tio • Channel estimation and correction using the pilot carriers.

a • I2C compatible interface (M-Bus) to the system controller.

m • Transmission Parameter Signalling (TPS) data is decoded and made available to the

r system controller via M-Bus.

Info 1.4.3 FFT Block

The FFT block performs the OFDM demodulation in the true sense of the word. It gets the time

ry domain information from the OFDM block, performs a Fast Fourier Transform on it and delivers

a the frequency domain information, i.e. the constellation diagram (suffering from the channel

in impairments) back again to the OFDM block.

lim Main features of the FFT block are:

e • Processing of one block of 2048 complex samples (i.e. one 2K-OFDM symbol) in 224 µs.

Pr • FFT input wordlength 8 bit, output accuracy selectable between 10 and 12 bit.

• Overflow on certain OFDM subcarriers due to co-channel interferes is handled internally.

1.4.4 Forward Error Correction Block

The FEC part of the DVB-T transmission is located in the blocks ‘FEC-Decoding’,

‘Deinterleaving’, ‘Sync-Inversion’ and Descrambling. All these tasks are handled by the FEC

block. The FEC scheme itself consist of the inner Viterbi decoder and the outer RS decoder.

1.4.4.1 Viterbi Decoder

The Viterbi decoder block is DVB compliant with all the coderates available according to the

specification. Its main features are:

• Maximum 37 Mbit/s output rate.

• Constraint length 7, generator polynomial (1718, 1338)

MOTOROLA

1-6

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

For More Information On This Product,

Go to: www.freescale.com

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