Design Of Digital Power Amplifier Based On Polar Coordinate Transmitter System

As the key role in the circuit system,the power amplifier finally transmits the signal to the antenna,so the various losses are the biggest.Due to its special function and irreplaceability,its efficiency is directly linked to the whole circuit system.How to develop a high-efficiency power amplifier is a key concern for engineers in the modern electronics industry;polar transmitter system as a new type of digital transmitter system using digital power amplifiers with the high efficiency characteristics which traditional Cartesian transmitter system analog power amplifiers can't achieve,and thus fully meet the needs mentioned above.This thesis mainly studies the basic working principle of the whole architecture of the new polar coordinate transmitter system and the working characteristics of the digital power amplifier based on this transmitter architecture,and realizes the design of high efficiency power amplifier.The research of the thesis first introduces the basic functions of each module in the RF link of the polar transmitter system and the working principle of the whole architecture.Then it focuses on the evaluation and design of the power amplifier module.The whole chip adopts the 65 nm CMOS produced by Hualian Electronics.The CMOS process is applied to the Bluetooth transceiver function in the 2.45 GHz band.The research is mainly based on the simulation design.The SpectrRF tool under the Cadence simulation software is used to first evaluate the performance of the basic unit structure under various conditions(D,E,F)of the entire digital power amplifier,according to various types of power in the application background.The power,efficiency,linearity and size of the basic unit of the amplifier are considered as the most suitable power amplifier type,and then the actual signal simulation is performed.Through the control variable method,the main reference is to optimize the efficiency and amplitude-amplitude distortion(AM-AM distortion)and amplitude-phase distortion(AM-PM distortion)of various types of digital power amplifiers under the specified conditions of 13 dBm output power.It shows that the digital power amplifier of SCPA structure has an almost ideal oblique AM-AM linearity while meeting the requirements of the output power and efficiency of the specification,and thus it is not necessary to add a module for correcting linearity in the former stage,so it is adopted,and still under the condition of post-imitation It can achieve nearly 35% efficiency while guaranteeing 13 dBm output power while having near-ideal AM-AM and AM-PM linearity with a swing of no more than 20°.In addition,an 8-bit thermometer encoding is used to input the amplitude signal to reduce the chip area occupied by the entire power amplifier module.Next,the transmit and receive conversion function are added to the entire chip,so that the power amplifier can maintain good performance while be connected to the low-noise amplifier module in the latter stage of the chip transmitter operating mode.and then the simulation shows that it is still have about 30% efficiency and good linearity at a 13 dBm output power.