In today's world, the development of communication technology is a rapid, accurate is man's desire for change... ), but the current human rely on wireless communication is completely done by radio, the following frequencies are mostly concentrated in the C band, pretty crowded, so, in order to increase the information in the limited spectrum resources transmission, signal modulation mode is more and more complex, appeared such as the 64 qam, 256 qam and many other non constant envelope modulation way, so, leads to the signal peaks are bigger than constantly, figure 1-1 is the instantaneous probability distribution and class AB amplifier signal envelope of instantaneous efficiency curve comparison chart (why and compare class AB? Because not so long ago base station power amplifier is the type),



FIG. 1-1 class AB amplifier efficiency of envelope and envelope probability distribution

See not hard, signal distribution near the modest average probability is bigger, too large and too small probability of signal is small, but can be found from the figure of the class AB amplifier efficiency as the signal power is increased, so near the average power amplifier efficiency is very low, when the base station power amplifier using class AB amplifier, often need to about 6 db from P - 1 db back to work, the efficiency will be dropped to 50% from 20% (for example, not sure data), don't look down upon oh, if the required output rated power of 100 w, fever, you calculate how much power, therefore the traditional class AB amplifier cannot meet the requirements of modern communication system for the power amplifier efficiency, so need to design efficient power amplifier to meet the needs of system for efficiency, you might say this if you have any difficult, with the switch type power amplifier (such as E class), with the harmonic control class amplifier (such as F class), the theory of efficiency of 100%, but, unfortunately, very difficult, the efficient amplifiers linear correction directly make do make dead (DPD algorithm to refuel oh... ), at the same time, the efficient work of the power amplifier bandwidth is not enough, the reliability is not good, but god never shuts one door but he opens another, thankfully, as early as 1936, W.H.D oherty invented Mr Doherty amplifier architecture, the architecture of the power amplifier, at the same time in the amplifier can back to work with high efficiency and good linearity, so what is the principle of power amplifier structure that the cow force, the following step by step to deconstruct Doherty amplifier architecture (for the interpretation of the following has the students understand the working principle of the power amplifier tube, don't know the power amplifier working principle of the classmates, please stop, catch up with the basic knowledge of first... ),