Multicarrier Uhf Band Adaptive Predistortion Feedforward Power Amplifier Design And Implementation

In nowadays, the society is demanding more and better mobile communicationbusiness, so the resource of frequency spectrum has become scarce, and mobilecommunication has meet with serious constraint. To this problem it is an effectivemethod to improve the data transfer rate and efficiency of utilizing frequency spectrum.So in modern system of communication the modulated signal which has high datatransfer rate, large variable range and high PAR is been used, but this give a difficultduty to the part related to radio frequency in the system. Especially in multi-carriertransmitting system the amplifier should meet the specified power and its efficiency,and the linearity would not lead distortion. However, these specifications of PA are incontradiction with each other, and can not be both achieved easily. So the research to PAwith high efficiency and linearity has gone to bottleneck, become focus in the world.In order to acquire high output power of transmitter and its efficiency in wirelesssystem, the amplifier is usually working close to the saturation, but by this thenon-linearity is so bad that the PA becomes a main origin of non-linearity, this wouldcause both distortion in the band and interference out the band, and the former increasethe bit error rate, the latter produce adjacent channel interference to decrease efficiencyof utilizing frequency spectrum because of spectrum spreading. To avoid this result thetechnology of linearization is used to realize the high efficiency and linearity of thesystem. Designing the RF power amplifier is always a problem in the process of the RFcircuit design. Power back-off technology was ever used to improve the linearity, butthe efficiency of power is decreased by this way. From then on, the technology ofnegative feedback, pre-distortion, feed-forward have been utilized successively, buteach has its own deficit.Against the status quo, and combining the feature of each method, this subjectresearch the self-adaptive pre-distortion feed-forward technology of linearization, so asto improve the linearity as well as the efficiency of the amplifier in the UHF. Because ofimporting self-adaptive module, the drifting of the environment factor like temperature,time would not affect the circuit, so that the system became more stable. The digital control system is used in the design, combined with the RF linearization system, whichis realized via the technology of pre-distortion and feed-forward, so as to acquire the RFoutput with high linearity and efficiency. The PA is composed of several subsystems,each is given system-level simulation in the design. In the subject, many parts involvewith amplifying circuits, vector adjustment, power coupling, etc. they are designed andsimulated to form modules of function. Combine these modules and debug the systemto achieve specified index. Compare the measured results with the simulated dada, andgive analysis to them in the dissertation. According to the measured result, the8-carriersystem has the IMD3of-57dBc and efficiency of13.5%when the output power is33.8dBm, consequently realized the designed goal of high linearity and efficiency.