Study On High-efficiency Rf Power Amplifiers With Dynamic Bias

Manufacturers face more and more pressure of the operating costs and energy efficiency. Therefore, the concept of green base station has been proposed. As the largest power dissipation component of green base station, the efficiency of the RF power amplifiers directly have influenced on the operation cost of base station. Hence it is quite urgent to find the solution of the high efficiency power amplifier. Based on the analysis of the merits of dynamic biases with the envelope tracking and the power tracking techniques, taking into account that the envelope tracking techniques is difficult to apply to the broadband RF power amplifiers, the power tracking technique is utilized to design the high efficiency power amplifiers with the dynamic bias, which has good performance of high efficiency, large gain and wide bandwidth in the TD-SCDMA operation band and also a very high value in engineering aspect.An RF power amplifier with dynamic bias will be designed in the first part. The techniques related to the PA design such as impedance match theory, dynamic bias theory will be argued and researched. Improved the traditional load pull theory, an optimization method which simultaneously scans the load and source impedance is proposed to determine the optimum load and source impedance. With two methods of Smith chart and the S parameter optimization, the designs of the matching circuits have been implemented. According to the results of comparison of two methods, the optimal impendence matching circuits have been achieved. Finally, the dynamic bias circuit is designed according to the power tracking, mainly including detector circuit design, voltage amplification circuit and its drain bias voltage varies in proportion to the amplitude of the input signal.The Second part mainly presents the testing results of the RF power amplifier with dynamic bias. Firstly, the power amplifiers have been tested with one-tone and two-tone signals. Then, the testing results have been compared between conventional power amplifier and dynamic bias power amplifier. Also, Analysis of the output spectrum of the power amplifier with one-carrier TD-SCDMA input signal. Finally, according to the probability density function of the input power, adopt a series of optimized and tested method, the average efficiency of the power amplifiers have been Calculated. The testing results show that this PA can achieve high power-added efficiency which presents 5% and 10% enhancement, respectively, compared to the conventional amplifier at 2.0175GHz of TD-SCDMA frequency when the input power changes. What is more, the average efficiency calculated according to the power added efficiency and the probability density of the one tone TD-SCDMA signal input has been improved nearly 6% from the 20% to 26%. The power...