The Design Of A Predistortion Power Amplifier Based On DGS

Mobile communication plays a very important role in the rapid development of society. With the production of the protocol of 3G mobile communication, and the short of radio frequency resources, the mobile communication will face challenges. Higher data transfer rate and high utilizing rate of the radio frequency resource are the most effective way to solve this problem, which lead to great change in modulation technique. As one of main module in RF system, RF power amplifier is essential in the development of mobile communication, and its performance limited the development of the mobile communication, so the development of the RF PA is very important. It has already been researched deeply in three points about the design of RF PA in this paper: design technology,linearization technology,Defected ground structure(DGS).The strengths and weaknesses of every method were analyzed thoroughly in this paper. According to the excellent performance demanded by the high-power RF PA, the design method of power amplifier based on Load-pull was proposed. Because the load-pull system can measure the impedance parameters of the RF PA exactly, so it is very suitable for the high-power RF PA design. This paper presents a measurement of FLL177 based on Load-pull system, and the PCB circuit has been implemented with these parameters. The testing result of the PCB circuit meets the requirements, it explains that the method based on Load- pull system can simplify the design process, can also get excellent performance.The nonlinearity of the RF PA would have a serious impact on mobile communication. In order to improve the performance of the RF PA, the predistortion technique which has many benefits like simple circuit and broadband signal is used in this paper. After the further analysis of predistortion, the innovative ideas will be made in this paper, and a circuit which can suppress the 3rd and 5th harmonics has been designed. The fundamental signal has been suppressed perfectly, when the predistortion signal generate. The predistortion circuit has been simplified and the performance has been improved in this way. Based on many simulations, the IMD3 and IMD5 are excellent suppressed in PCB circuit.The harmonics which impact the output power can't be ignored when a RF PA designed. DGS which have filter characteristic is analyzed thoroughly in this paper. DGS used in the terminal of the output matching networks in PA can suppress the harmonics which don't increase the size of the PA. The test results of the DGS PA verify that the output power and efficiency of the PA have been improved by DGS.