Feedforward Power Amplifier Research And Design

In mobile communication systems, information transmission is developing sharply in the direction of increasing channel capacity, dynamic range, output power level, and frequency bandwidth. The new generation of mobile communication system puts forward higher requirements for the linearity of amplifiers. Particularly to power amplifier, its linearity will directly affect the performance of the whole system. Due to the stability and high linearity of feed-forward technique, it is the fastest-growing linear technology.This master dissertation analyzes the working principle of RF power amplifiers, in particular its non-linear characteristics, and then raises several amplifier linearization techniques, such as power back-off technique, negative feedback technique, pre-distortion technology, and feed-forward technology. The dissertation highlights the work principle of the feed-forward amplifier circuit, and then quantitative analysis of the key components parameters in the system.This master dissertation simulates the feed-forward amplifier system and its key components by ADS, and makes the budget distribution for the components, takes further analysis on design ideas and elements of feed-forward technology; and then eliminates distortion signals by power combiners and couplers, and studies the difference of the system output power and inter-modulation distortion under different situations through its simulation results.Finally, this master dissertation describes the entire design process of the main amplifier and the auxiliary amplifier according to the requirements of the simulation system, including selection of the transistors, amplifier design structure, etc. The dissertation makes the one-tone test and two-tone test for the main amplifier and the auxiliary amplifier respectively. One-tone test is used to analyze the influence on output power and gain of supply voltage of the power amplifier circuits at all levels, and also two-tone test is used to get the amplifier output power, gain and inter-modulation distortion, results of which basically achieved the established targets. In the last of this paper, the test results reflect the feasibility of this design; at the same time analyze some indicators which do not meet the requirements.