Radio Frequency Power Amplifier And Microstrip Circuits Design

With the rapid development of the wireless communication, the increasing number of the users and limited spectrum recourse require higher spectrum exploited and higher date ratio. Power amplifier, as one of the core components for the wireless communication systems, its performance has a great effect on the communication quality of the system. The current use of the multi-carriers cause a high power to average ratio strongly requires that the power amplifier should have sufficient linearity, while the base stations demand high efficiency as well as the terminals. To insure the communication quality, power amplifiers is confronted with the severe challenges for higher linearity and efficiency. Therefore, more and more linearization and efficiency enhancement techniques have been adopted for power amplifier to settle these problems.The dissertation theoretically analyzed the non-linear characteristics of the power amplifier and the common non-linear power amplifier models. Comprehensive comparisons were made for various the linearization techniques and efficiency enhancement techniques with their characteristics and complexities. The first key work here focused on the Doherty power amplifier, which has a distinguished feature of active load pull effect as an efficiency enhancement technique. Doherty power amplifier is characterized by its high efficiency for a wide range output power back off without using additional periphery circuits. This is due to its special biases setup for the carrier amplifier and peaking amplifier which results in two kinds of operating modes according to the input signal lever.The theoretical analysis of the Doherty work principles and the requirements of working patterns in the low and high lever range were presented. And the current trends of the Doherty power amplifier design were also described. For the traditional Doherty power amplifier, the current of the peaking amplifier could not get to the maximum allowable level that the load modulation of both amplifiers was unable to achieve the optimized impedance at the maximum output and resulted in the efficiency degeneration because its low bias. A novel inverted Doherty structure which exchange the output power combined point improved the efficiency of the Doherty power amplifier effectively. A three stages cascaded Doherty power amplifier was constructed for the wireless mobile base station with high gain and high efficiency. An advanced design method of uneven power drive was applied to enhance the peak envelope power output ability and the efficiency at the high level range. Then an experiment was implemented to verify the linearity difference between Doherty power amplifier and Class AB amplifier for theoretical analysis.The defected ground structure (DGS) was studied based on the classic dumbbell shape as a hotspot of the microstrip circuit researches. The effect of its dimension parameters on the frequency response was carried out and three types of equivalent circuit pattern extraction methods were also summarized. Several kinds of novel DGS unit were proposed and their equivalent circuit pattern and their elements values were extracted from their electromagnetic simulation. And the novel DGS units were utilized for low pass filters and multi-band pass filters design. A new dual mode transmitter was made by combined a broadband power amplifier with the DGS for its bandgap property, and the experiment results show the validity of the design.Finally, two low insertion open loop resonator bandpass filters with 0o feed stucture for wireless local area network (WLAN) were presented, and the filters were optimized with DGS and Spurlines for wide stopband range, respectively. The final part was the ultra-wideband (UWB) filter design and the main work focused on the hybrid microstrip/CPW structure with multi-mode resonators (MMR). The characteristics of the MMR were analyzed and several types of the UWB filter were proposed with single notch at 5.8 GHz or dual notchs by using tight coupling.