An Improved Design of Feed-forward Power Amplifier

Amplifier’s nonlinear phenomenon is the significant factor that affects the performance of radio & microwave communication system. In this paper, the principle of feed-forward technology and various improved solutions are introduced. Meanwhile, aiming at their shortages of classic feed-forward and OCFF topology, a new high linearization solution is proposed for the large power output, which reduces difficulty of the error amplifier design and input power. The results show it can improve the power efficiency remarkably without adding the complexity of the system, which is of practical value for improving the communication quality. DOI: 10.2529/PIERS060817033556 With the development of large capacity 3 G mobile communication, owing to adding channels, branching the bandwidth and employing higher frequency modulation method, the higher linearization for the power amplifier is especially important for communications system. The linearization matter has been one of the key issues of the new generation mobile communication system [1]. In radio & microwave communications system, nonlinear character of power amplifier is the most resource to result in the system’s nonlinear. Therefore, it is meaningful for the communication development to analyze the nonlinear character and to study on the simple, feasible Linearization method of the power amplifier. At present, the linearization technologies for RF & microwave power amplifier are classified into four kinds: power back-off, feedback, predistortion and feed-forward, which are different in system architecture and advantages. Especially the double loop feed-forward topology, which is applied widely in many productions owing to its high performance, better linearization, wider available bandwidth. For the present, many papers focus on the parameter optimization and controlling the phase and amplitude, meanwhile, there are some papers researching on improving the performance of passive element. But few people pay attention to improve the system solution [6]. In this paper, the classic feed-forward technology and various improved solutions are introduced, at the same time, aiming at the shortage of the classic feed-forward and OCFF technology, a new improved measurement for large power output is presented, the results show it can improve the power efficiency remarkably and reduce difficulty of the assist amplifier design without adding the complexity of the system.