DAB digital broadcasting is the third generation of broadcasting after AM and FM traditional analog broadcasting-digital signal broadcasting. Its appearance is a revolution in broadcasting technology. Digital broadcasting has anti-noise, anti-interference, anti-fading of electric wave propagation, and is suitable for high-speed Mobile reception and other advantages. It provides CD-level stereo sound quality, with almost zero signal distortion, and can achieve "crystal-transparent" audiophile-level broadcast sound quality. The DAB receiver module from Shenzhen Niura is used in the development of DAB digital broadcasting .
DAB/FM radio is a fashionable Walkman Digital Radio (DAB) and Digital Automatic FM radio. This receiver has the characteristics of high sensitivity and low power consumption, and uses an internal lithium-ion battery to supply power. Listening to DAB and FM through headphones and speakers is excellent. Use a 3.5mm double-head stereo audio cable to connect the DAB receiver to the audio amplifier input (Aux-in). This radio can also be used in cars and home audio. This kind of radio supports all DAB III bands (China and Europe), and it will become popular within 10 years.
1. Basic introduction
DAB is the third generation of broadcasting after AM and FM traditional analog broadcasting-digital signal broadcasting. Its appearance is a revolution in broadcasting technology. Digital audio broadcasting not only transmits audio, but also transmits related information (road conditions, weather, news, etc.), and even transmits images. In addition to strong anti-jamming and anti-interference capabilities, the transmitted signal attenuation is also low, so that the transmission and transmission distance of digital broadcasting stations can be longer and the coverage rate can be wider. [1] It provides CD-level stereo sound quality that can reach "crystal-transparent" audiophile-level sound quality. It is especially suitable for broadcasting "classical music", "symphonic music", "pop music", etc. It is extremely popular with professional musicians and music Sought after by audiophiles and audiophiles!
2. Brief history of development
The development of DAB technology originated from the German Institute of Broadcasting Technology in 1980, using the Eureka-147 system to conduct research on terrestrial audio broadcasting technology. In 1985, Germany and began DAB pilot experiments in Munich. In 1986, the governments and broadcasting organizations of Germany, Britain, France, the Netherlands, Denmark and other countries formed the Eureka alliance with the electronics industry and formulated the Eureka-147 DAB specification. The DRM system was proposed by France in 1996. The DRM alliance was established in Guangzhou, China in 1998. It was formally launched in July 2003. There are currently about 30 member countries, and about 27 DRM systems are officially operating in the world. Although mainland China It is a member of the DRM Alliance, but currently still uses Eureka-147 as the main DAB experimental specification. The IBOC system has other uses for the frequency planned by Eureka-147 in the United States, but it is proposed to master the development technology of digital broadcasting and use the existing AM and FM frequency bands as the research and development work of IBOC. Because the sound quality has not improved so far, the current reform Use IBOC HDC encoding and decoding technology for R&D and testing
3. Listening technology
According to the current popular statement, DAB is the product of the migration of audio transmission from the analog era to the digital era. It is also the third-generation broadcasting system that came out after AM and FM. But what is even more interesting is that by relying on DAB, in theory you can use your eyes to "listen" to the broadcast-due to the digital nature, DAB can transmit any text or even image signals. So you can connect the DAB radio to the TV to restore the video image in the digital signal. In this sense, DAB is no longer a pure broadcasting system that only transmits audio signals.
Even in terms of radio quality, DAB broadcasting has a great advantage compared with analog radio. The signal-to-noise ratio of DAB broadcasting is at least 95db, and the encoding rate is above 192Kbps, which has exceeded the sound quality level of most MP3s. At the same time, due to the characteristics of anti-interference and anti-wave attenuation of digital signal transmission, DAB broadcasting is very suitable for use in fierce mobile environments, such as vehicles.
In terms of user experience, DAB radio is also completely different from traditional AM/FM. DAB broadcasting only requires the user to remember a very limited number of frequency bands-each frequency band belongs to a specific comprehensive radio station, and each radio station can set up 5-6 channels in this frequency band. For a classical music lover, the typical procedure for listening to DAB radio is: tune to the "broadcast frequency" where the radio station (such as BBC) is located, then enter the music sub-channel under it, and finally enter the classical music channel, just like The same as opening the menu.
In fact, DAB has become the standard for digital audio broadcasting in Western European countries such as the United Kingdom. At present, the most influential DAB standard is Eureka-147, commonly known as "European Regulation", but its use area is not limited to Europe. In addition, IBOC (In-Band On-Channel) formulated by the United States and DRM (Digital Radio Mondiale) formulated by France are also two important DAB technical standards in the world. As the signing place for the DRM standard that was just established in July 2011, China has become one of the 30 members of the alliance. Through cooperation with the European Union, China has established a DAB laboratory in Beijing, and has already started building a DAB pilot network in Guangdong and conducting DAB broadcasting. [2]
4. Features
On the basis of COFDM technology, DAB adopts time interleaving and hierarchical error-proof protection, making DAB mobile characteristics almost perfect. DAB's spectrum bandwidth is 1.5MHz; data bandwidth is 1.2M, with time division function, when users choose After the program is finished, the DAB decoder only needs to decode the required DAB symbols, so the time division function is very effective. According to the code stream of the selected program, the power ratio of the DAB decoder can be reduced to 20%-50% of the full power. One of the reasons for DAB's global popularity is that among many digital mobile standards, DAB is the most mature and has ready-made stations and network facilities available. It is a technology that realizes handheld mobile digital reception with small engineering volume, low cost and better performance. . [3]
5. Differences
The biggest difference between DAB and traditional broadcasting (FM, AM), in addition to DAB's transmission quality and technology of CD sound quality, DAB also has the ability to receive multimedia information, including text, data, pictures, images, and even real-time information updates. Therefore, the application of DAB is not limited to audio broadcast services, but more importantly, data broadcasting services. Therefore, many scholars and experts refer to DAB as Digital Broadcasting.
6. Development status
Although it has been nearly 25 years since the advent of DAB technology, it is only within 10 or even 5 years that it has truly entered civilian use. The sharp price reduction of DAB radio has become the rapid development of DAB radio in some countries from 2003 to 2004. The most important factor in popularity.
In 1996, when DAB broadcasting was just launched in Foshan, the only DAB radio available in China was a model that could only receive audio signals provided by Philips, and its price was as high as £4,200. But since 2003, the price of the cheapest home and car DAB radios in the UK has fallen to 80 pounds and 400 pounds, respectively. The domestic Tsinghua University is also actively developing high-quality and inexpensive DAB radios for domestic use.
It can be said that listening to DAB broadcasts has become a fashion, and more and more hardware manufacturers are responding. At the CeBIT exhibition held in 2012, iRiver, a major digital audio equipment manufacturer, launched a DAB radio with the model iDA-100. Although it supports the playback of popular audio files such as MP3, the battery life is only as short as 7 hours, so iDA-100 should indeed be a "radio supplemented by MP3 playback." In addition, TerraTec, a sound card manufacturer with the same reputation as Creative, has also entered the DAB field.
In China, in addition to Guangdong and Beijing, the two regions where DAB applications were the first to start, DAB applications have also been implemented in Tianjin and Henan. And Philips also launched a car radio that can receive DAB broadcasts in China in August.
7. Product Application
There are currently more than 60 types of DAB digital broadcast receiving terminals, including MP4, PMP, GPS navigator and USB receivers.
(1) Navigation application
The navigator using DAB technology can understand real-time road condition information, weather conditions, and the openness of elevated ramps just like receiving broadcasts. Compared with previous navigators using TMC technology, DAB technology covers a wider area, and the listening signal and sound quality are better. And because of the way similar to the radio, there will be no traffic charges.
(2) Mobile TV application
The DAB mode can bring convenience to mobile TV users, such as convenient reception, rapid transmission, wide coverage, and mobile reception. Free is the biggest benefit DAB brings to users. Mobile TV users can not only listen to traditional audio broadcast programs, but also listen to and watch multimedia information such as videos, data, text, and pictures, including real-time traffic information, weather information, and so on. [4]
8. How to receive
To receive DAB programs, you must use DAB dedicated receiving equipment to listen to or watch the programs or information you want to receive. DAB receiving equipment can be roughly divided into car type, home type, portable type and computer receiving card. General household, car and portable type DAB receiving equipment are roughly the same as today's FM/AM receiver. The computer receiving card's DAB receiving The equipment, in addition to receiving general audio programs, can also receive text, pictures, images and other content at the same time. Because it is installed on a computer and integrated through the Internet, the application level is more flexible and extensive; the current more expensive car and portable type The receiving DAB receiving device also has most of the functions that a computer receiving card can achieve.
(1) Receiver
Not all digital receivers are DAB receivers. There are many digital receivers on the market, but most of them are analog FM, AM broadcast and satellite broadcast receivers manufactured by digital technology. Such receivers are called digital Receiver. The DAB receiver must comply with the Eureka 147 technical specifications in order to receive DAB signals.
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