A Volterra-Series-Based Nonlinear Analysis Of Radio Frequency Power Amplifier

With the development of wireless communication, the communication speed becomes faster than before. Based on the high speed transmission scheme of the communication system, a strict requirement for the power amplifier is linearity. The wireless transmission system increasing pushes the demands for the linearity of RF power amplifier. To design a linear power amplifier with high efficiency has become a key technology.Traditional power back-off method is able to improve the power amplifier’s linearity, but it brings an obvious sacrifice on power added efficiency. The novel methods enhance the linearity, however, add complexity by additional circuits. Based on the widely used class AB amplifier, this thesis studies the technique to improve the linearity avoid adding system complexity.Volterra series theory is an effective method to analyze nonlinear behavior. Volterra kernel functions have a definite physical meaning in both time-domain and frequency-domain. Therefore Volterra series method is a suitable option for engineering application. Based on the power amplifier’s characteristics, this thesis sums up a completed set of analysis technique using Volterra Series theory. And this analysis technique is used to develop the system behavior model of the amplifier circuits. The matching circuits, compensation network and bias circuits are then studied by this mean.Experimental results verified the effectiveness of this design method.1. In the research of the common emitter amplifier, IM3(3rd order Intermodulation) is suppressed by more than6dB with the design in harmonic load impedance of output matching network.2. In the research of the cascode amplifier, OIP3(Output3rd Order Intercept Point) is improved by3dB with the design of RLC compensation network.3. In Class AB power amplifier design, the best bias circuit for the balance between efficiency and linearity can be calculated by using the Volterra technique. An analytic expression between the bias circuit and AM-AM is achieved in design stage, so the period of power amplifier’s design and experiment can be shortened.