Discussion on digital modulation technology and terrestrial digital TV broadcasting

Discussion on digital modulation technology and terrestrial digital TV broadcasting

Abstract: The development of terrestrial digital TV broadcasting in China is inseparable from the support of digital modulation technology. The reception and transmission of signals are disturbed by many uncertain factors, which seriously affects the stability of the whole system. The normal operation of terrestrial digital TV broadcasting needs to ensure the scientific rationality of its signal generation and transmission process. The transmission of digital broadcast signals and the modulation of related frequencies are limited by some international standard protocols. To do a good job of terrestrial digital TV broadcasting, we must master the relevant principles of digital modulation technology involved.

Keywords: digital modulation technology; Terrestrial digital television broadcasting; Agreement; signal

Early TV broadcasting generally used analog modulation technology, which was related to the signal source itself. With the expansion of the research scope of communication technology, digital modulation, as a brand-new means of communication technology, has a far-reaching impact on the development of terrestrial digital television broadcasting. Digital modulation technology corresponds to related demodulation technology. In practical application, both of them play a very obvious role in TV broadcasting.

1 Overview of related principles of digital modulation technology

The gradual maturity of digital modulation technology has directly promoted the development of terrestrial digital TV broadcasting in China. The main ways to transmit data are single carrier modulation and multi-carrier modulation. The main contents of these two technologies are also the main development direction of digital broadcasting system. Whether serial data transmission mode or parallel data transmission mode, representative data frame, as a special symbol, plays a decisive role in the selection of modulation mode. Only when these data frames are loaded on the carrier by modulation can a digital transmission signal with a certain frequency be formed. In the process of signal transmission, there is the concept of channel. At the same time, in the process of amplitude and phase modulation of carrier, there are also related principles of symbol mapping. All marking points represent the amplitude and phase of the carrier, and the relationship between them belongs to orthogonality. Different coordinates represent the difference of carrier amplitude and phase, which is of great significance to the research of digital modulation technology. Because the relationship between the amplitude and phase of the carrier is almost orthogonal in practical research, the distribution of plane coordinates also shows certain regularity. Therefore, the positional relationship of carrier-related parameters is also called symbol mapping of constellation. In modulation technology, the amplitude and phase of carrier wave change with the change of waveform, and the representation of plane coordinates is one-to-one correspondence, so it becomes a mapping relationship. Phase and amplitude are the main technical parameters to measure the carrier change, so they are used as symbols to simulate the actual waveform change. So all the labels in 1 have a specific meaning, which is called the symbol mapping of constellation. The main principle of single carrier modulation is that in the process of carrier waveform change, a symbol frame represents a complete whole, and all different waveform changes form a symbol frame. The existence of these symbols is mainly to show the changes of carrier technical parameters during modulation. These technical parameters mainly include the amplitude and phase of the carrier. All symbols are arranged in the form of strings, and finally form a single carrier. The so-called multicarrier mainly means that in the process of symbol frame composed of all symbols, the carrier corresponding to each sub-symbol is no longer the same carrier. Corresponding to different carriers, special output signals are finally formed through superposition processing.

2 Summary of technical standards related to terrestrial digital television broadcasting in China

The reference standard of terrestrial digital TV broadcasting in China was formulated late, but it also formed a certain system. This paper mainly emphasizes the reference standard of channel coding in transmission system and related carrier technical parameters. Commonly used are multi-carrier transmission mode and data frame structure of GB20600.

2. 1GB20600 data frame structure analysis

Three different frames in GB20600 constitute the corresponding PN sequence. The transmission time of these frames in the transmission system is different. The time that a data block occupies in the frame body is about 500 microseconds. Due to different PN sequences, the time occupied by signal frames is also very different. For the carrier of transmission system, the difference of these technical parameters has great influence on the reception and transmission of broadcast and television signals. Terrestrial radio and television transmission system makes full use of the relevant principles of digital modulation technology. For the frame header and frame body involved, the time occupied by the channel coding process is different.

2.2 Related principles of multi-carrier mode

The related technical principles of multi-carrier transmission mode are very complicated in structure and transmission mechanism. The number of symbols corresponding to its frame body and frame header is different. Generally speaking, the frame body consists of 3780 symbols, which means that 3780 different carriers play their respective roles. For China's terrestrial digital TV broadcasting transmission system, the application of multi-carrier technology plays an important role in the stability of signal transmission system. In multicarrier transmission mechanism, PN sequence plays an important role in the estimation of the whole channel and noise suppression. When the wireless channel works normally, it is easily affected by noise, which is very unfavorable to signal transmission. The related phase noise must be suppressed by related technical means, which has a great influence on the normal mechanism of the whole channel. Among them, the guard interval is a prominent feature of multi-carrier mode, which plays a major role in resisting multipath interference. Only by removing some valid data can we achieve the ultimate goal of suppressing noise.

3 Conclusion

In the development of modern communication, modulation technology plays a vital role in signal transmission. The main parameters of carrier refer to amplitude and phase, which has important reference significance for the research of terrestrial digital broadcasting. Digital modulation technology has a far-reaching impact on the stability of the whole system. Only by understanding and mastering the relevant principles of digital modulation technology can we make greater contributions to the construction of terrestrial digital broadcasting in China.

References:

Yang Zhixing, Wang Zhaocheng. Key technologies of the next generation terrestrial digital television broadcasting system [J]. Television Technology, 20 1 1, (8): 22-27.

[2] Bai Yang, Feng Jingfeng. The key technology to realize the network modulator of terrestrial digital TV broadcasting single frequency network [J]. Broadcasting and TV technology, 201,(12): 50-53.

Li Ling. Research on QDPSK digital modulation and demodulation technology [D]. Nanjing University of Science and Technology, 20 14.

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