Slip Imbalance, The Linc Transmitter System

LINC(Linear Amplification using Non-Linear Components)technique is becoming one of the main techniques on resulting nonlinearity in the power amplifier. With the rapid progress of wireless communication, problem in the scarcity of radio resources turns to be obvious gradually. How to make use of radio spectrum resources adequately has been placed on the agenda. However,emergence of data transmission techniques and digital modulation techniques with high ACPR, whose spectrum efficiency are higher, have introduced a severe challenge to linearity technique of power amplifier. As a big breakthrough in improving linearity of power amplifier, LINC technique could make power amplifier's efficiency achieve 100% in desirable condition. It is not only the perfect unite of digital technique and analogous technique, but also the perfect unite of high linearity and high efficiency. For more than 30 years LINC technique has become research hot spot in wireless communication field home and abroad. Its key technique and algorithm, such as design in algorithm of the compensation on gain and phase imbalances, and design in SCS (Signal components Separator) in the structure with feedback loop circuit, need to be researched deeply.This thesis carried out a deep research in algorithm of compensation on gain and phase. LINC transmitters are sensitive to the imbalances existed in the system because of its special structure. The imbalances could affect its quality badly and make the spectrum of output signal spread largely. Not only the linearity of system would decrease but also the goal to reach 100% efficiency would go further. First, this thesis introduced the linearity techniques of power amplifier briefly. Then LINC technique's development status, development trend home and abroad and its several main techniques were introduced in detail. After introducing the principle of LINC technique and the imbalances in gain and phase, both of which are the key problems in LINC transmitters, were researched in detail. The contribution of the Signal Component Separator, the Quadrature Modulation, the Power Amplifier and the Combiner to the effect of imbalances in gain and phase have been analyzed in theory respectively in order to solve these problems. Through analysis and summary about gain and phase imbalances, this paper proposed an algorithm and then optimized it to make this algorithm converges faster with smaller error. This algorithm has presented good convergence and robustness through the simulation in a new LINC transmitter system. Finally, a LINC system testing platform was established on DSP and the module was tested. Then good effect on compensation on the gain and phase imbalances has been proved. Not only the ACPR has been decreased but also the LINC's linearity has been improved.