Pick   want:       This paper introduces the DMB-T standard definition receiver top box solution built by LGS8222 , which has the characteristics of superior performance, simple structure and low cost. Overview Digital Terrestrial Television Broadcasting (DTTB) since November 1998 launch in North America and Europe, many countries have entered the business in the operational phase. There are currently three international standards for digital television (DTV) terrestrial transmission, namely: the US ATSC system using 8-VSB modulation , the European DVB-T system using COFDM modulation, and the Japanese ISDB-T system using BST-OFDM . Based on the advantages of these three terrestrial transmission standards, Tsinghua University Digital TV Technology Research Center introduces new technological achievements in the field of communication, and proposes a brand new ground with independent intellectual property rights for TV broadcasting. digital multimedia / television broadcasting standard (Terrestrial digital mulTImedia / TV broadcasTIng, DMB-T) scheme. It uses Time Domain Synchronous Orthogonal Frequency Division Multiplexing (TDS-OFDM) modulation, which is unique and effective in system frame structure, synchronization, channel estimation, guard interval, symbol mapping, error correction coding and system implementation. The technical solution has a great improvement in anti-multi-channel noise, multipath, Doppler fading, clock recovery, transmission efficiency and the like. Tsinghua University Digital TV Technology Research Center The latest generation of receiver-specific chip model for DMB-T solution is LGS8222 . This article will briefly introduce the solution for using DGS -T protocol standard definition set-top box built with LGS8222 . system introduction As shown in Figure 1 , the main components of the DMB-T SD set-top box include: tuner, DMB-T channel demodulation chip, MPEG-2 decoder chip, power supply unit, various peripheral memories and amplifiers. Standard definition set built demultiplexer, MPEG-2 decoders and PAL / NTSC encoder, and an infrared remote control interface of the 81MHz CPU. The system uses 16 MB of SDRAM as the memory shared by MPEG and CPU , and uses 4 MB of flash memory as the program memory. The set-top box input is a radio frequency signal conforming to the DMB-T specification, and the output is an audio and video signal. In order to facilitate the vehicle, the power input of the set-top box is DC 12V , and the total power consumption of the system is 8W . To facilitate monitoring of reception performance, the set-top box also provides a bit error indication signal. Figure 1 DMB-T set - top box block diagram  Figure 2 LGS-8222 system block diagram  Figure 3  DMB-T standard definition set-top box The key parts of the block diagram are briefly described below. High frequency head The DMB-T uses a tuner similar to the DVB-T system's tuner, and all DVB-T- capable tuner can be used in the DMB-T set-top box. Thomson and Sharp have high-frequency heads with related functions. Thomson 's DTT7578/7579 ( vertical / horizontal ) is used in this solution . It is a high-frequency head developed by Thomson for digital terrestrial television broadcasting. Its operating frequency range is V segment (177~227MHz) and U segment (470~860MHz) , and the output is intermediate frequency 36MHz . There are two levels of AGC -RF AGC and IF AGC inside the tuner . The total gain of the two-stage AGC is 90dB . The DTT7578/7579 is powered from a single supply and requires various voltages to be provided by an internal DC/DC converter. The control of the tuner is implemented via the I2C bus. DMB-T channel decoding chip LGS-8222 is the latest DMB-T- compliant single-chip channel receiving demodulation chip developed by Tsinghua University Digital TV Technology Research Center . It has good receiving performance under various complicated conditions. Its functional block diagram is shown in Figure 2 . . The LGS8222 has a built-in high-performance A/D converter. The A/D converter performs digital-to-analog conversion on the input analog IF signal, then synchronizes, equalizes, and corrects the signal, and finally outputs the MPEG-2 code stream. The main features of the LGS-8222 chip are as follows: MPEG-2 decoder chip The STI5518 is a powerful and low-cost new MPEG-2 decoder from ST . It is an upgrade of the company's set-top box decoder STI5500 (OMEGA) . The STi5518 retains all the features of the STi5500 and adds support for Dolby Digital and MP3 audio decoding. Additional logic is added to facilitate the connection of hard drives, making them ideal for emerging "converged" products that provide features such as pauses for live TV and playback of recorded TV shows. The STi5518 integrates on one chip: a transmit signal splitter module, an ST2032 -bit CPU , an audio / video MPEG-2 decoder, display and graphics functions, a digital video encoder, and system peripherals. The STi5518 can be seamlessly integrated with the LGS8222 to implement the DMB-T receiver set-top box. Conclusion The DMB - T standard definition receiver set-top box built by LGS8222 has the characteristics of simple system, low power consumption ( the power consumption of the whole set-top box is about 8W) and low cost, which provides a strong guarantee for the development of terrestrial digital multimedia broadcasting services. Figure 3 is a photograph of a standard definition set-top box of DMB-T constructed using LGS8222 . ■references: 1.  LGS-8222 instruction manual 2.        STi5518 instruction manual 
