Design Of High Power Communication Amplifier Model

The current wireless communication systems have made significant progress toward wide band and high-data-rate applications, but the high peak-to-average ratio (PAR) signals require linearly amplify. Power amplifier is the most energy-intensive components in Base station system. Unfortunately, the efficiency of linear amplifier is usually very low, especially far away from the maximum output power point. Effective measures are urgently needed to improve the efficiency for the linear area(power back off PAR), also asked a simple structure,stable performance.Doherty amplifier can keep high efficiency over an extended power rang. Mainly simply constituted by a class C and class AB amplifier. Based on the analysis of basic power amplifier theory and key performance, the Doherty amplifier's principle,structure,development were discussed in detail. Finally, under project background, a base station amplifier model,50.3dBm average output power, used for the 6.0dB PAR 4 carrier GSM900 MHz signals amplification, has been completed. The author's main task is the RF amplify part design, including driver amplifier,uneven power divider,the end stage Doherty amplifier design. Efficiency of the model is more than 38% when work at average out power. The model gain is 58.5dB under the test result. Based on the target impedance design method and CAD software, schematic and electromagnetic simulation, PCB and practical model has been accomplished.The actual testing proves the model has required performance.The main design and key of this work has been focused on the final stage amplifier. The amplifier's small size, video bandwidth (VBW) and other properties have been specially designed. In order to improve the efficiency and power amplifier performance, the power divider ratio for main amplifier and peak amplifier has been adjusted to 1:1.2.The efficiency of the final amplifier reached 45.5%, compared with ordinary class AB amplifier increased by about 6 percentage points. Video bandwidth is 32MHz under the definition of 2dB IMD asymmetry.