The Polar Transmitter Based On Envelope Elimination And Restoration

With the continuous development of modern communication technologies,the application of various wireless terminal products and various non-constant envelope modulation technologies with high spectrum utilization rate and transmission rate are emerging.The use of OFDM and other multi-carrier non-constant envelope modulation technology,but also produce a larger peak-to-average ratio,in the traditional orthogonal transmission system,the RF power amplifier mainly uses a linear power amplifier,so the need for a larger transmitter The power back-off ensures that the transmitter power amplifier operates in the linear region,which results in a significant reduction in transmission efficiency.Therefore,in terms of peak-to-average ratio signals,in order to ensure high transmission efficiency and low signal distortion,it is of great significance to design an efficient transmitter architecture.At present,there are many transmitter architectures that improve the efficiency of power amplifiers,based on envelope elimination and restoration.Polar transmitters are the ideal choice.The polar transmitter based on envelope elimination and recovery is a radio frequency transmission system that can theoretically satisfy both high transmission efficiency and low signal distortion.Different from the traditional orthogonal transmission system,the architecture decomposes the baseband signal into the envelope and phase signals through amplitude and phase separation,and then phase information is carried on the RF carrier through phase modulation.Finally,the signal is composited to eliminate the envelope signal.Recovery,due to the constant envelope characteristics of the phase signal,allows the transmitter power amplifier to always operate in the linear region without requiring power backoff,thereby improving the transmission efficiency.In this paper,the background significance of research on polar transmitters,the research status at home and abroad,and the achievements are briefly introduced.Then the traditional and digital implementation schemes of the transmission architecture are compared.First,the basic principles of the transmission system based on envelope elimination and restoration are introduced.The key techniques of amplitude and phase separation,delay estimation and delay adjustment,and multi-sampling rate signal processing involved in the transmission architecture are introduced.The influence of the branch delay mismatch on the entire transmitter is also analyzed.The FPGA hardware design of the system includes the amplitude and phase separation module,the delay estimation module,the signal processing module and the external communication interface module.Finally,the test platform and the scheme are introduced,and the influence on the transmitter performance before and after the delay adjustment is analyzed.