| With the rapid development of digital television broadcast toward network and information, DTTB (digital television terrestrial broadcast) will lead a revolution of broadcast technology. At the present, there are various analog television transmitters in different transmission stations in our country, along with the coming of DTTB times, it is unpractical to change all of those transmitters, and the transmission of analog to digital television must come through the process of coexist, so it is significant for the technical analysis of analog television transmitter for digital television terrestrial transmission.In the first chapter, a brief explanation of three DTTB transmission standards: (ATSC of American, DVB-T of Europe, ISDB-T of Japan) adopted by the International Telecommunication Unit is given, and DTTB transmission standard research in our country is introduced. This chapter also gives introduction of digital television transmitter development both in domestic and abroad.The second chapter gives detailed analysis of digital television multi-carrier wave transmission, according to digital television terrestrial transmission scheme, and the theoretical analysis for the property of time domain and frequency domain of orthogonal frequency division multiplexing (OFDM) signal is given. In study with the characteristic of OFDM, this chapter points out the requirement of digital television signal on television transmitter, including radio frequency(RF) spectrum, intermodulation distortion (IMD),amplification channel, the stability of frequency and the output filter. By theoretical analysis this chapter proves and reviews the special technical requirement of OFDM modulation for analog television transmitter RF channel.In the third chapter, the peculiarity of television transmitter power amplification channel is analyzed according with the concrete analog television transmitter model (France THOMCAST E UHF 10000DD), the composition of the module's circuit and the power combination mechanism are thoroughly studied. By mathematics models of the power amplifier and the OFDM signal as asequence of random process. Using nonlinear random process analysis, this chapter deduces the theoretical result of the high degree intermodulation distortion caused by the nonlinearity of the amplifier. So that, it is become the key problem to improve the linearity of power amplifier for analog television transmitter for OFDM signal transmission.the froth chapter gives detailed analysis and comparison on series linearized technique of television transmitter power amplifier, emphasis is on power back-orTx feedback correction x feedforward correction and digital auto adaptive predistortion back on dual-LUT, and with the peculiarity of television transmitter amplifier, the chapter pointes out the technique feasibility and the restrictiveness in engineering realization of those correction scheme. Based on the result of analysis and study described above, this chapter gives a digital auto adaptive predistortion correction method-complex gain Look-Up Table (LUT) baseband digital predistortion technique, and computer simulation on this technique is carried out. This method has peculiarity of easy to realize, has relative less limitation on the element, and the correction loop convergence speedily. A good result of high degree intermodulation distortion compression is obtained in the computer simulation.In the fifth chapter, two correction schemes for analog television transmitter RF channel for digital television transmission are given, based on the result of theoretical analysis and computer simulation with the circuit transmitter model.This paper analysed in detail the technical requirement of analog television transmitter RF channel for digital television transmission in theory. Systematic study is made on the improvement of the linearity of analog television transmitter power amplifier for digital television signal transmission. This paper makes productive study on the analog television transmitter for digital television terrestrial transmission. |
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