Designing & Researching Of A-Doherty Amplifier With LDMOS FETs

With the rapid development of wireless communication industry in recent years, the band resources are increasingly scarce, higher spectral efficiency modulation techniques have emerged, such as 4G communication standard TDD-LTE uses OFDM technology, which It means to transmit the signal has a higher PAR. The higher PAR put forward higher requirements that power amplifier linearity,through a certain power backoff can effectively improve the linearity of the transmitted signal, but this would mean inefficient power amplifier, power amplifier is the largest component of energy consumption in the wireless communication base station, the efficiency of the system will directly determine the level of efficiency, and therefore the power amplifier must still be able to maintain high efficiency over the range of power back-off, otherwise the power amplifier heat dissipation problem becomes very serious, and will resulting in a serious waste of power resources, which is obviously contrary to the current concept of the communications industry, "small station" "green station" in. Through efficiency enhancement techniques can solve the above problems, the most commonly used efficiency enhancement techniques include LINC Technique, EE&R Technique, Outphasing technique, ET technique and Doherty technique. Doherty technique because of its relatively simple structure and ease of implementation become one of the most feasible, cost-effective, the most mature technology commercialization. However, Doherty technology, there are some disadvantages, so its academic improvements proposed A-Doherty amplifier, it has also become one of the hot current base station power amplifier.During the joint training of the author of this article in the Micro-electronics Research Institute, according to research in conjunction with the Micro-electronics Research instructor arrangement made according to the specific job content writing we are engaged.First article on power amplifier design specifications, design methods, a detailed description; secondly analyzes the Doherty amplifier works, and pointed out the reasons for its shortcomings exist; then, the traditional Doherty power amplifier to improve proposed A-Doherty amplifier, and focus from "different power transistor" and "unequal power-driven" perspective, combined with practical examples and theoretical formula analyzes the reasons for the relative improvement of conventional Doherty amplifier; and finally, based on the requirements TDD-LTE communication base station simulation designed and implemented the rollback amounted to a 9.5 dB of high power and high efficiency a-Doherty amplifier, after a lot of testing, the test results meet the requirements of the system indicators. The test results show that this section A-Doherty amplifier saturation power up to 330 Watts(55.17 dBm), the saturation power point PAE of 52% rollback 9.5 dB PAE of 40% relative to the symmetric Doherty amplifier backoff 9.5 dB when PAE can be increased by 10%, for a class AB amplifier when the same amount of retraction PAE can be increased by 20%, fully embodies the a-Doherty amplifier huge advantage in the communication base station and ease of implementation for the communications industry " small station " " green station " and other demands is a very large significance.