Broadband Doherty Alternative with Filter Design Considerations

Abstract

Doherty Amplifiers have become the standard architecture for high-efficiency cellular infrastructure applications, but most designs in production and in the field are limited in RF bandwidth (RFBW). Though it would be desirable to have Doherty amplifiers that operate over several adjacent bands, the importance of system efficiency under corrected linearity conditions has limited the deployment of wider-bandwidth Doherty amplifiers. This is particularly true where amplifiers require peak power capability of 500W or greater. This paper discusses filter design techniques related to RF power semiconductors targeted for wideband Doherty operations, as well as an amplifier technique that we call Frequency Selective Broadband (FSBB) Doherty design-this technique allows an alternative amplifier design covering multiple operating bands, without trade-offs in efficiency performance.