Patent ID: 7741907

Claim:
A class-F amplifier comprising: an amplifying element configured to output an output signal including a component of an angular frequency ωo of an input signal, and harmonic components thereof; a first reactance circuit interconnecting an output terminal and a ground terminal of the amplifying element; a fundamental matching circuit disposed at an output terminal end of the amplifying element; a second reactance circuit connected between an input terminal of the fundamental matching circuit and the output terminal of the amplifying element; and a load interconnecting an output terminal of the fundamental matching circuit and a ground terminal, wherein the amplifying element has as an output impedance that is an impedance of a parallel circuit comprising an output resistor and an output capacitor, the first reactance circuit is configured to be open for a dc component, shorted for components of angular frequencies 2ωo, 4ωo, . . . , 2nωo, where n is an arbitrary integer of 1 or more, and parallel resonant with the output capacitor of the amplifying element for components of angular frequencies 3ωo, 5ωo, . . . , (2n+1)ωo, the second reactance circuit is configured to be shorted for a dc component, and open for components of angular frequencies 3ωo, 5ωo, . . . , (2n+1)ωo, the output capacitor is connected in parallel with the first reactance circuit, having a circuit having an admittance Yp(s) to be open for a dc, shorted for angular frequencies 2ωo, 4ωo, . . . , 2nωo, and open for angular frequencies 3ωo, 5ωo, . . . , (2n+1)ωo, and the amplifying element is a high power element that has an output impedance with a lower impedance value than the load, which narrows the bandwidth for the angular frequency ωo of fundamental wave to be matched, when the output capacity Co is large so that the bandwidth is prevented from getting narrower, the admittance Yp(s) is conditioned, in its partial fraction development: Yp(s) =Hp·s+Yp1(s) such that Hp=Co, the second term Yp1(s) represents an admittance of the first reactance circuit, the first reactance circuit gets parallel resonant with the output capacitor of the amplifying element for odd harmonics, permitting the impedance seen from the output resistor with the load inclusive to be open for odd harmonics, allowing for a class-F operation at high frequencies where the output capacitor of the amplifying element is non-negligible.