Where V dcrepresents the dc voltage at the drain, V d1is the amplitude of the fundamental component of the drain voltage and V dn is the amplitude of the n th odd harmonic component of the drain voltage. Idealized waveforms of the drain current and voltage in the class F power amplifier.In other words, the input impedance of the drain network represents an open circuit to the odd harmonics and a short circuit to the even harmonics. Accordingly, the drain to source voltage at the device output contains only odd harmonics while the drain current contains only even harmonics. These resonators must present open circuit (harmonic peaking) to the odd harmonic components and short circuit (harmonic termination) to the even harmonic components at the device output. If the RF device is assumed to operate as a switch then the shaping of the drain waveforms can be changed by controlling the harmonic components of the drain voltage and current through the insertion of multiple harmonic resonators in the output matching (or load) network of the power amplifier. As seen from this sketch, there is no overlapping between the drain voltage and current waveforms, which means zero dissipated power in the RF transistor and thereby leading to 100% theoretical efficiency. The idealized operation of the class F RF power amplifier imposes the drain (or collector) voltage to be shaped as a square wave and the drain (or collector) current to be shaped as a half-wave sinusoidal waveform as shown in Fig.1.
Advanced design system 2017 equation portable#
The simulated results have indicated that the circuit gives a dc-to-RF efficiency of more than 84 % and a power gain of 11 dB at 500 MHz with an operating bandwidth from 440 to 540 MHz.Ĭlass F RF power amplifiers are finding widespread applications in modern portable and base station transmitters due to their high-efficiency operation.
To confirm the approach of analysis, a 10 W class-F UHF power amplifier circuit has been designed and simulated using a typical Gallium Nitride high electron mobility RF transistor (GaN HEMT) to operate at 500 MHz with the aid of the Advanced Design System (ADS) computer package. The benefits of this topology include simplicity of design, controllable bandwidth, and harmonic tuning and impedance transformation at the same time. The proposed network consists of a parallel short circuited λ/8 stub, parallel open circuited λ/8 stub, and a T-section lumped-element transformer. In this paper, a new load network for class F power amplifiers has been introduced and derived analytically. To do this task, a suitable load network is to be synthesized in order to present the proper harmonic impedances at the output of the RF power transistor. Class-F RF power amplifiers offer improved efficiency over conventional class-B power amplifiers by properly controlling the harmonic components of the voltage and current signals at the output terminals of the RF device, while driving it to operate as an ON/OFF switch. High efficiency RF power amplifiers are increasingly employed in modern mobile communication systems to reduce battery size and power supply consumption.
0 kommentar(er)
