Polar Transmitter Circuits Based On Cordic Computer

The continuous development of information technology has pushed the wirelesselectronic equipment towards lower power, low cost and better-performed. The bestway to meet the requirement of modern advanced wireless communication is utilizinghardware circuits based on CMOS IC(Integrated Circuit) technology. Among the circuitblocks, transmitter always plays a significant role in many wireless applications.Theresearch on high-efficient and low power transmitter circuit is always a hot issue in bothindustrial design and academic research, and draws a lot interest from worldwide.This thesis mainly focuses on an approach to improve the performance oftransmitter at its circuit structure and topology level. At the beginning,the basicconcepts and structure of quadrature modulation based transmitter were introduced. Thequadrature transmitter system separates the series baseband signal stream into twoparallel sub-streams,and it employs a couple of LO(Local Oscillator) signal with a fixedphase difference of90degree to realize up-conversion. The signal paths of this structurecan be divided into I(in-phase) path and Q(quadrature-phase) path since the quadratureLO signals on each path. The main drawback of quadrature system is the mismatchbetween I and Q path, this would cause serious harm to total performance.To improvethis, a new transmitter structure based on polar modulation is proposed in this thesis.Unlike quadrature structure, polar modulation converts parallel signal to its relativepolar formation,by using two new variables amplitude A(t) and phase Φ(t), throughamplitude modulation and phase modulation separately, the combined signal at output isequivalent to traditional modulation system.The proposed structure mainly consists ofthe signal form conversion block, phase path, envelope path.Based on Cordic computer, signal form conversion block is built in Modelsimplatform, it separates the desired signal from initial I and Q. Also, by using ADS andTSMC0.18μm RF CMOS PDK(Process Design Kit), a class E power amplifier with18dBm output power and power added efficiency of60%in X band realized.Thesystematic verification work is done compared to quadrature modulation.