Generation Mechanism for 3^<rd> Order Inter-Modulation Distortion in Harmonic Frequency Controlled Ultra-High Efficiency Amplifier

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Circuit synthesis methods for class-F high efficiency microwave amplifiers have been proposed, where up to 7^<th> order higher harmonic frequencies are taken into consideration in the design. In the class-F microwave amplifiers, load impedances for a transistor are zero at even order harmonic frequencies and those are infinity at odd order harmonic frequencies. Because of intervention of output parasitic capacitance such as base-collector capacitance in heterojunction bipolar transistors(HBT), the open circuit condition for the transistor is difficult to be retained. In addition, circuit losses in class-F load circuit degrade power efficiency also. In this project, using the ISE-TCAD two dimentional device simulator, optimum doping density for HBT collector has been derived for the class-F amplifier operation. And also introducing low loss resin circuit board with tan δ=0.0023, class F load circuit considering up to 7^<th> order harmonic frequencies were designed and fabricated in a di … More stributed circuit form. Fabricated InGaP/GaAs HBT class-F amplifier circuits operating at 1.9 GHz delivered 74.2% measured PAE(Power Added Efficiency) and 76.6% measured collector efficiency. In the case that circuit loss is de-embedded, the PAE is 78.7% and the collector efficiency reached 81.2%. These values are bench mark results in microwave amplifiers operating around 2 GHz.In a 3^<rd> order inter modulation distortion view point, not only a fundamental frequency, but also harmonic and sub-harmonic frequencies should be taken into account, since frequency mixing phenomena among these frequencies take important rolls for distortion generations. In FET class-F amplifier, short-circuited conditions for even order higher harmonic frequencies bring about less distortions, since generation mechanism via even order higher harmonic frequencies are deleted. However in the HBT class-F amplifiers, because of existence of large base to collector capacitance, the distortion generation mechanism are more complicated. It has been pointed out that self compensation among multi vectors for 3^<rd> order inter-modulation distortion signals occurs. In a view point of sub-harmonic frequency termination conditions, short circuited filtering circuits at bias supplying networks are found to be effective to reduce the distortions for both two tones and W-CDMA signals. Less