A broadband Doherty power amplifier without a quarter-wave impedance inverting network

A new Doherty power amplifier topology without a quarter-wave impedance inverting network is proposed. This topology enables the enhancement of amplifier bandwidth and achieves a more compact amplifier size. In order to remove an inverting network, the output matching network of the carrier amplifier is designed to realize high performance both at a low-RF level in the off-state of a peaking amplifier and at the RF saturation level. A 1.9-GHz Doherty amplifier without a quarter-wave impedance inverting network was designed and fabricated using GaN HEMTs. A series-connection-type amplifier using an output-combining balun was realized in a lumped-element circuit configuration. The amplifier achieved a power-added efficiency (PAE) of 51% at an output power of 29 dBm under an 11-dB input back-off from a 34-dBm saturated output power with a power-added efficiency of 59%. A maximum PAE higher than 48% was obtained over a frequency range of 1.67 to 1.97 GHz.