Predistort-linearization RF Power Amplifier Design

The requirements, of the linearity of RF power amplifier (RFPA) which come from thewide application of linear modulation techniques and the rapid development of fourthgeneration cellular mobile communication system have been improved. It is a difficultproblem that there are inter-modulation distortions which are generated by the characteristicof these linear modulation techniques that envelope is dynamic when modulated signalthrough RFPA results in the detrimental effects that distorting the amplitude and the phase,enlarging the spectrum, worsening the bit error rate (BER), disturbing the adjacent-channelsignals, and etc. Therefore, the research of linearization technology, in order to meet thelinearity and efficiency requirements of RFPA, has become a focus.This thesis makes a research on the RF digital pre-distortion technology which appliesto design, in accordance with the demands of RFPA such as high-linearity, high-gain andhigh-power from a wideband wireless communication system project, a linear RFPA, after theanalyzation of the non-linear characteristics and the non-linear mathematical model,introduction of current linearization techniques, and the discussion of advantages anddisadvantages of these linearization techniques. The research, presented above, it is made oftwo parts:1. A50W linear solid-state RFPA module based on LDMOS has been designed. Thisthesis through the discussion on method for the design of power amplifiers, analyzation of theperformance and optimization of circuit simulation, makes the module which is applied to aspecific project of the wideband wireless communication system to achieve the followingspecifications.a. working frequency band:225MHz to512MHz;b. gain≥36dB;c. gain flatness≤±1dB;d. VSWR≤1.5;e. When output power(P-1db) is greater than50W, IM3≤-25dBc.2. A linearization RFPA applying RF digital predistortion technique which based on thetruncated Volterra model has been designed. This thesis through those means which are design,manufacture and testing of the actual circuits whole the process makes the RFPA to have agood linear effect that IM3Less than-40dBc, which improved about20dB when poweramplifier output power greater than50W. The design and test of the RFPA based on RF predistortion technology symptomatizethat the technology can reduce the RF power amplifier distortion and increase output powerwhile maintaining good linearity, effectively improve the power efficiency of the systembetter. Therefore, RF predistortion linearization technology is a promising linearizationtechnology.