| With the rapid development of wireless communication, technologies of complicated high-order modulation and OFDM are used to improve the spectrum efficiency. The Peak to Average Power Ratio (PAPR) of the signal increases and the efficiency of the power amplifier (PA) will decrease. Envelope tracking (ET) technology attracts much attention for the reason that it is an effective method to improve the PA efficiency. This thesis focuses on the ET technique. The Envelope Amplifier (EA), which is the key part of the ET system, is designed and optimized in this thesis. A hardware platform of this EA is implemented. The platform is tested and the results are shown and analyzed.Research progresses of high efficiency PAs are summarized. ET is one of effective methods to improve PA efficiency for advantages of large danymic range and small signal distortion. Simulations of the ET system have been done to study both the advantages and disadvantages of this power modulation technique.Then, three EA implemetation methods based on linear mode, switching mode and hybrid mode amplifiers are analyzed respectively. The switching mode EA has the potential to adopt new techniques and to have better performances. Two schemes of the switching mode EAs are proposed in this thesis, which are optimized schemes based on multiple power supplies and adaptive multiple power supplies. Simulations have been done for these two schemes and the simulation results are analyzed in the thesis.Finally, the scheme of ET system with adaptive multiple power supplies is implemented and the hardware platform is established. Signal testing has been done on this platform. In addition, the hybrid mode EA system is established and tested. The simulation results are shown and analyzed. |
PDF Full Text Request