Abstract-In modern mobile communication systems, spectral efficient modulation formats have been widely used, which results in the envelope of the radio frequency (RF) signal is variable and having large peak to average power ratio (PAPR). In order to amplify the RF signal without distortion, the linear power amplifier (LPA) is adopted, which is less efficient when powered by constant voltage. Three popular techniques, i.e., Doherty, envelope elimination and restoration (EER), and envelope tracking (ET) techniques, to greatly improve the efficiency of the power amplifiers are analyzed and compared in this paper, and it is shown that the ET technique is the most suitable for future mobile communication systems. In the ET systems, the ET power supply is the key equipment, which dominates the system efficiency. With the development of the mobile communication systems, the bandwidth and the PAPR of the envelope signals are increasing rapidly, which pose severe challenges on the design of the ET power supply. This paper summarizes and sorts the ET power supplies in the literatures, and a detailed comparison is presented to guide the selection of ET power supplies for different applications. Finally, the methods, including soft-switching, slow envelope, and band separation are proposed for further increasing the efficiency of the ET power supply.Index Terms-Band separation, Doherty, envelope elimination and restoration, envelope tracking, power amplifier, slow envelope, supply modulator, soft-switching.
I. IntroductIonT HE mobile communication brings convenience of real-time communicating to people in a mobile state without physical transmission line, and it has been continuously developing ever since its advent in 1970s [1]. The first-generation (1G) mobile communication systems adopted analog electronics technology and can only provide voice service. Furthermore, it suffered poor anti-interference ability and slow data transmission rate. The second-generation (2G) mobile communication systems employed digital electronics technology, and they can transmit and receive voice and text message. With the rapidly increased customers and the demand for multi-media service, the data transmission rate is required to be faster, and the third-generation (3G) and fourth-generation (4G) mobile communication systems emerged in succession, which makes the video calling service and internet surfing into reality [1].With the development of mobile communication, the power consumption increases rapidly, accounting for about 10% of the global power generation. Thus, it is necessary to reduce the power consumption of the mobile communication. In mobile communication systems, the base stations consume the majority of the power. In a base station, about 50% of the power is consumed by the power amplifier, and its loss is dissipated as heat, which requires extra power to cool down. So, increasing the efficiency of the power amplifier is the basis of reducing the overall power consumption of the mobile communication.In 2G mobile communicatio...