| The performance of the output matching circuit is one of the most critical roles in designing well-performance power amplifier. However, when choosing the transmission line for circuit design, there is a problem usually neglected by the designers, which is power loss of the output matching circuits. The power loss occurs in the capacitors, inductors, transmission lines of the matching network, and other energy components. Power loss may cause serious impedance mismatch of power amplifie, and then more power can be reflected to input location. Even the power will be dissipated in term of thermal. Therefor, it will significantly drop the efficiency and output power capability of power amplifier.The paper mainly introduces power losses and thermal characteristic for the matching circuit of power amplifier. A matching circuit module is working at the frequence 2.0GHz, which is connected to the 50Ωconnecter at the input and output, which is used the microstrip technology for the input and output matching circuit. The paper maimly includes:1. Introduce the development of microwave power amplifiers and their categories, as well as its technical specifications and requirements.2. Analyze the characteristic impedance of microstrip line, transmission characteristics and other parameters, as well as note in the practical design.3. Grasp to design the matching circuit of the power amplifier rapidly and present every step in the way of clear and methodical analysis.4. Use Agilent's software ADS(Advanced Design System) to design and simulate three different topologies of matching circuits, and generate PCB (Printed Circuit Board) board.5. Propose the test solution of the matching circuit of power amplifier, and offer test results. Afterward Propose a better analysis, which can be comprehensive understanding of the electromagnetic and temperature performance of matching circuits. At last, compare the performance of the three output matching circuits.The study can be found that energy loss in the single and double stub matching circuits cause the phenomenon of bright and shade. However, the hotspot of the quarter wavelength transformer occurs at the dicontinuity. The power will be dissipated in the way of heat, which will make the local temperature rise. Even the power radiates significantly, which could make the transmission line bend and impedance dismatching, Moreover, it will affects output power.The paper is the first trial that research the electrical and thermal characteristic using the microstrip for matching circuit of power amplifier. There are some issues that will be solved, but it provides a new method of how the matching circuit deal with the impedance diversification due to the power losses and thermal change. The method is not only suitable to matching circuit of power amplifier, but also it provides a good guideline for other matching types. This method of measurement will continue to develop in the study in the future. |
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