Improvement of Doherty amplifier efficiency with new low-pass filter using Photonic Bandgap characteristics

In this paper, the power added efficiency (PAE) of a Doherty amplifier has been improved by applying Photonic Bandgap (PBG) characteristics on the output of amplifier. The new low-pass filter (LPF) using PBG characteristics is adopted on the output offset transmission lines. As a result of the high order harmonics termination, excellent improvement in PAE, maximum output power as well as linearity is obtained. The PAE is improved as much as relatively 35% compared with a conventional Doherty power amplifier. Moreover, size of LPF is reduced by PBG characteristics. Therefore the whole amplifier circuit size is considerably reduced by diminishing in size of the LPF as compared with a Doherty amplifier using conventional LPFs.