| With the rapid development of wireless communication, linear modulation techniques andhigh-efficiency RF power amplifiers are widely used to make more efficient use of frequency spec-trum and achieve greater efficiency. RF amplifiers usually use power back-off to achieve the system’slinearity requirement under non-constant envelope modulation. However, in order to improve outputpower and efficiency of power amplifier (PA), PA always works in saturated state, which will produc-es nonlinear distortions. The nonlinearity causes distortions within the signal bandwidth, which de-creases the bit error rate at the receiver. It also creates spectral growth beyond the signal bandwidth,which interferes with adjacent channels.For achieving high linear and reasonably efficient power amplifier, we always use linearizationtechniques in general. In the all linearization techniques, digital predistortion (DPD) is the most effec-tive way for its advantages of stability, high efficiency, wide-bandwidth and adaptive. To study digitalpredistortion system, it is required to understand the nonlinear characteristics and memory effects ofPA, and to build exact behavioral model of power amplifier. In this paper, following contents are dis-cussed and studied, including nonlinear characteristic and distortion of power amplifier, memory ef-fect and cancellation of power amplifier, PA behavioral model and digital predistortion system. Ac-cordingly the research works are as follows:1. Introduce the basic theory of power amplifier and analyzes the nonlinear characteristics andits influence, also analysis the memory effect and the influence of predistortion system.2. Designed a class AB power amplifier applied in GSM frequency and test the PA.3. Designed a Doherty power amplifier based on a class AB PA with ADS.4. Introduce the models and linearization methods of power amplifier, proposed a new prunedVolterra Model based on memory and nonlinearity function for power amplifier. Built expe-riment platform with Matlab and instrument, linearized a Doherty power amplifier with dig-ital predisitortion based on the proposed model. |
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