The Enhancement Techniques Of The Efficiency And Linearity For Broadband CMOS Radio Frequency Power Amplifier

In recent years,with the rapidly development of the wireless communication,the demand of wireless communication system is increasing.Meeting the demands of multiple-wireless communication applications,the systems working in parallel is one of the important tendencies of future.Simply stacking the system will significantly increase the cost and volume of the equipment,and the mutual interference between the systems will significantly reduce the overall stability.Therefore,the multi-standard communication transmitters have become a main developing trend.Meanwhile,with the development of CMOS process,the performances of analog modules and digital modules have improved rapidly,but the performance of the power amplifier(PA),which is the important device of the transmitter,gets worse.With the progress of CMOS technology,the characteristic size and breakdown voltage are decreased and the output power,efficiency and linearity of PA are also decreased.With the diversified working modes,higher transmission rates and a variety of communication protocols,bandwidth,efficiency,and linearity are the main development directions of PA.Although high-efficiency and high-linearity PA have been developed in recent years,they are all based on single-frequency or narrow-band applications and cannot be used in broadband applications.Therefore,the broadband high-performance PA is presented in this paper.The performances of the PA are related to the amplification and transmission characteristics.MOSFET directly affects the amplification characteristics of the PA.So the characteristics and models of MOSFET are discussed.The differences between CMOS and Ga As processes are compared from two aspects of material and stacked structure and the advantage of the CMOS processes is provided.The relationship between the DC performance,small signal performance,large signal performance and physical size of MOSFET is also researched.The development history of the MOSFET model is introduced.A novel MOSFET large-signal model is proposed and the parasitic effects of the large signal model are introduced respectively.For the proposed large signal model,two sets of model formulas are put forward: the first model formula is the relationship between the parasitic parameters and device physical size;the second model formula is the relationship between the S parameter and parasitic parameters.The transmission characteristics of the PA are dependent on the matching network.The conjugate matching network,which is based on the entire design process of an actual wideband PA,is briefly introduced.The load-pull matching technique is compared with the conjugate matching technique for highlighting its importance for PA designing.The relationship between the optimal load and frequency of the common source PA and cascode PA is analyzed by using the novel MOSFET model.The formula can be used to reduce the frequency effect,so as to enhance the saturated output power and the efficiency of the PA.The influence factors of the bandwidth expansion in PA have been introduced.So the bandwidth of the derivative superposition technique in linearity improvement technology and variable bias technique in efficiency improvement technology are expanded.First,the bandwidth of the variable bias technology,which is used for enhancing the efficiency of the PA,was expanded.The sub-threshold power detector is used as the bias generator to expand the bandwidth of the variable bias technology.This technology is combined with the optimal impedance analysis of the cascode structure in Chapter 4 for improving the efficiency of the broadband PA.Second,the negative feedback resistance and cross coupling capacitance are used to expand the bandwidth of the derivative superposition technique,so that can be applied in the broadband application.The optimal linearity technique is applied in 45?2500 MHz CMOS driver PA for improving the linearity of the PA.In addition,the chip of 45?2500 MHz CMOS RF front end are completed.Finally,the broadband CMOS PA and the RF front end are taped out and measured.