Abstract: A high-frequency power amplifier comprises a pair of FETs, a divider which supplies opposite-phase versions of a signal to be amplified to the FETs, distributed-parameter transmission lines connected respectively at one ends thereof to output electrodes of the FETs, and a combiner which combines signals appearing at another ends of the transmission lines into a signal of a common phase. Stubs which short-circuit for even harmonics included in output signals of the FETs are connected respectively to the transmission lines at positions distant from the output electrodes of the FETs by a multiple of a quarter wavelength of the fundamental wave included in the output signals of the FETs.

Abstract: Disclosed is a microwave solid-state amplifier arranged such that a plurality of amplifier units are used in combination of a radial cavity resonator so as to perform power dividing/combining, and that in order to make the microwave solid-state amplifier capable of performing a wide band operation and have less circuit loss, a coupling portion between the radial cavity resonator and each of the amplifier units is formed such that a loop-like conductor constituted by a stripline forming an input/output portion of the amplifier unit is removably inserted through a slot formed in a side wall surface of the cavity resonator.