A new circuit topology to realize high efficiency, high linearity, and high power microwave amplifiers

The unexpected and unprecedented growth in demand for increased communications capacity by telecommunications consumers has led to the implementation of a variety of multi-spectral digital modulation techniques. All of these have in common the need for improved amplifier linearity in order to be practical or to co-exist with other users in the same spectrum. Many systems also mandate that the amplifier efficiency be as high as possible to extend the operating time of portable or self-contained power sources. In addition to the above, many systems desire relatively high power outputs to be obtained for improving reliability or availability. A workable compromise is difficult to achieve for any given set of parameters. Much effort in the literature is devoted to designs of amplifiers that seek to meet the above requirements. In this paper, work that was reported previously is extended to a more general higher power case by introducing a previously unknown circuit topology variation of a microwave Doherty amplifier. The new topology shown easily extends the load line modulation principle to higher power designs while also providing a design technique that avoids many of the complications of two tightly coupled interactive stages. A brief review of previous work is included for completeness.