LAUSR

In this letter, a distributed element‐based load network is proposed for designing a high‐efficiency dual‐band (DB) 5‐W Class‐E power amplifier (PA), at two widely spaced frequencies of 2.4 and 5.8 GHz. This network consists of two different stages. The first stage deploys a flexible network configuration with crossed transmission lines (TLINs) to provide concurrent DB fundamental matching in a closed‐form derivation, which transforms the standard resistance of 50 Ω directly to the optimal complex impedances. By tolerating the combination of the up‐side and down‐side TLINs, the size of the overall circuit as well as the implementation complexity are reduced. The second stage uses a DB TLIN‐based resonator preceded by a series 50 Ω stub to control the harmonic impedances without altering the fundamental impedances, ensuring high efficiency at the fundamental frequencies. The measured prototype shows highest power added efficiency (PAE) of around 62.9% and 61.7% with output power of about 39 and 35 dBm at 2.45 and 5.76 GHz, respectively.