What is Digital Television Radio?

Digital television is also called digital television or digital television, which means that all links from the studio to transmission, transmission, and reception use digital television signals or all signal transmission to the system is composed of 0 and 1 digital strings. The type of television that is transmitted by a binary digital stream, as opposed to analog television. The signal loss is small and the receiving effect is good.

Digital television is also called digital television or digital television, which means that all links from the studio to transmission, transmission, and reception use digital television signals or all signal transmission to the system is composed of 0 and 1 digital strings. The type of television that is transmitted by a binary digital stream, as opposed to analog television. The signal loss is small and the receiving effect is good.

Chinese name

Digital television broadcasting

Foreign name

Digital television broadcasting

applied Science

Communication

Digital TV Broadcasting Development

The third-generation television, marked by high-definition television (HDTV), has become the development direction of a new generation of digital televisions due to its ideal audio-visual effects and multi-function. In order to achieve a definition higher than 1000 lines, when MPEG-2 compression coding is used, the HDTV source coding rate will reach 25MHz. In order to use the existing analog channels (bandwidth of 6 to 8MHz) to transmit broadcast HDTV, channel coding must be performed to compress the transmission bandwidth.

At present, there is no uniform international standard for channel coding and modulation. And the modulation method will be different depending on the media (satellite, terrestrial, cable) that can be used for digital television broadcasting. For example, a single-carrier signal is used in a satellite communication system. While external coding is used, punctured convolutional coding is added internally. The modulation method of the signal generally uses four-phase phase shift keying (QPSK); wired cable communications generally have no additional internal Coding, the modulation method in Europe uses Quadrature Amplitude Modulation (QAM), the United States also recommends QAM modulation, but some cable TV operators advocate the use of residual sideband modulation (VSB); the modulation used in terrestrial broadcasting In terms of differences, Chinese national standards use time-domain synchronous orthogonal frequency division multiplexing (TDS-OFDM) technology, European and Japanese standards use orthogonal frequency division multiplexing (OFDM) technology, and the United States uses VSB modulation.

It can be seen from the above description that the development of HDTV will face two main problems: the first is the coexistence of multiple systems, and the second is the smooth transition from analog TV to HDTV. The HDTV solution based on software radio technology can well solve the problems faced by the development of HDTV.

Digital TV broadcasting composition

The basic structure of digital TV broadcasting system broadcasting and receiving consists of the following three subsystems.

(1) Source coding and compression subsystem. The subsystem receives analog video and audio signals through an analog-to-digital converter (ADC) and converts them into a digital bit stream, then compresses it with MPEG-2, and adds control and auxiliary data.

(2) Service reuse and delivery subsystem. This subsystem combines video, audio, and auxiliary data streams to form packets, adds tags, and packets form a single data stream. These multiplexing tasks are controlled using the MPEG-2 delivery system syntax.

(3) Transmission subsystem. It includes channel coding and modulation for multiplexed data streams.

The application of software radio in digital TV broadcasting system mainly involves the transmission subsystem in digital TV broadcasting system.

The basic idea of software radio is based on a universal, standard, and modular hardware platform. Software programming is used to implement various functions of the radio station. It is liberated from the hardware-based, application-oriented single station design method, as much as possible. Many communication functions are realized by software. In this way, the development of new communication systems and new products will gradually shift to software.

Figure 1 shows a physical picture of a digital TV modulator USB card. It has software development kits based on Windows 2000 / XP and Linux, and supports programmable RF output levels (0.1dB steps). The supported modulation methods include: DVB-T / DVB-H, ATSC8VSB, QAM, DVB-S / DVB -S2, T-DMB, ISDB-T, SBTVD-T and DTMB, etc.

Based on the principle of software radio, a block diagram of a digital TV broadcasting system can be constructed (as shown in Figure 2). The universal modulator in the figure completes the functions of channel coding and signal modulation before frequency conversion of the signal.

Figure 1 Digital TV Demodulator USB Card

Figure 2 Software Radio Digital TV Transmitter Block Diagram

This software radio-based digital TV broadcasting system implements the main functions of the system with software, which can be applied to different transmission media (such as wireless, cable and satellite digital TV), generate digital TV signals of different standards, and perform different bit rates. Encoding, and has a strong ability to upgrade the system. When a new signal processing method (such as a new coding method, modulation method, etc.) appears, only new software can be loaded to realize the digital television broadcasting of the new standard, which not only reduces investment, but also shortens the cycle of product development.

The significance of digital TV broadcasting

In the production of digital television receiving equipment (including digital televisions and digital television set-top boxes), the problem of receiving multiple systems should be considered, which is of great significance for improving the coverage of digital televisions and reducing the cost of viewing. According to the principle block diagram of the transmitting end of the digital television broadcasting system based on software radio technology, the principle block diagram of the digital television receiving system based on software radio technology can also be conceived (as shown in Figure 3). The system can receive digital TV with different transmission methods through different software loaded.

Figure 3 Software Radio Digital TV Receiver Functional Block Diagram

The main difficulty in implementing a digital television broadcasting system based on software-defined radio technology is to require low cost. If the cost is too high, it will become a bottleneck that limits its development. It is believed that with the development of microelectronic technology, this software-based digital TV will have a good development prospect.

Software-defined radio can well solve the two problems of coexistence of multiple systems in digital television, and the smooth transition from existing analog television to HDTV, and can provide a powerful impetus for the development of digital television broadcasting systems.