Patent ID: 7602241
Filing Date: 2009-10-13
Classification: H03F

Abstract:
1. A multiband Doherty amplifier comprising: a divider for dividing an input signal into two divided signals; a carrier amplifier connected to one output port of the divider, for amplifying one of the divided signals; a delay element connected to the other output port of the divider, for delaying the other divided signal; a peak amplifier connected to an output port of the delay element, for amplifying an output signal thereof; an impedance converter connected to an output port of the carrier amplifier, for performing an impedance conversion; and a combiner comprising a first cascade connection of N impedance conversion transmission lines connected at a joint at which an output port of the peak amplifier and an output port of the impedance converter are joined, for combining the output signals therefrom and performing identical impedance conversion for each of N frequencies, N being an integer equal to or greater than 2; wherein an electric length of the delay element is equal to the electric length of the impedance converter, the impedance converter comprises a second cascade connection of N impedance conversion transmission lines, each having a different line width, performing identical impedance conversion for each of the N frequencies, and the first cascade connection of the combiner causes, while the peak amplifier is in amplification operation, a load impedance seen from the joint to match an output impedance seen from the joint for each of the N frequencies.