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Digital radio is radio that uses digital technology to transmit and/or receive across the radio spectrum. In many modern systems, the radio signal is a digital signal that has been produced using digital modulation. Digital radio receivers also exist, that decode analog radio signals using digital electronics. ==Types== 1. Today the most common meaning is digital radio broadcasting technologies. In these systems, the analog audio signal is digitized, compressed using formats such as mp2, and transmitted using a digital modulation scheme. The aim is to increase the number of radio programs in a given spectrum, to improve the audio quality, to eliminate fading problems in mobile environments, to allow additional datacasting services, and to decrease the transmission power or the number of transmitters required to cover a region. However, analog radio (AM and FM) is still more popular and listening to radio over IP (Internet Protocol) is growing in popularity. In 2012 there are four digital wireless radio systems recognized by the International Telecommunication Union: the two European systems ''Digital Audio Broadcasting'' (DAB) and ''Digital Radio Mondiale'' (DRM), the Japanese ''ISDB-T'' and the U.S. or Arab World ''HD-Radio'' (IBOC). 2. An older definition, still used in communication engineering literature, is wireless digital transmission technologies, i.e. microwave and radio frequency communication standards where analog information signals as well as digital data are carried by a digital signal, by means of a digital modulation method. This definition includes broadcasting systems such as digital TV and digital radio broadcasting, but also two-way digital radio standards such as the second generation (2G) cell-phones and later, short-range communication such as digital cordless phones, wireless computer networks, digital micro-wave radio links, deep space communication systems such as communications to and from the two Voyager space probes, etc. 3. A less common definition is radio receiver and transmitter implementations that are based on digital signal processing, but may transmit or receive analog radio transmission standards, for example FM radio. This may reduce noise and distortion induced in the electronics. It also allows software radio implementations, where the transmission technology is changed just by selecting another piece of software. In most cases, this would however increase the energy consumption of the receiver equipment. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Digital radio」の詳細全文を読む スポンサード リンク
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