class-F RF Research Articles

High gain over an octave bandwidth class-F RF power amplifier design using 10W GaN HEM

The wireless communication industry grows faster each day. In terms of RF power amplifier (RFPA), the requirements on efficiency, linearity, bandwidth, output power and cost are getting more stringent. RFPA is considered as the most important component because of consuming large power in a base station. In this paper, a systematic approach is used to design a high flat gain class-F RFPA over an octave bandwidth. The simulation of a 1.5GHz class-F power amplifier mode demonstrates a high drain efficiency while accomplishing a high flat gain over a wide bandwidth. To identify the optimum impedance for the output matching and input matching network, the load-pull and source-pull are performed. The simulation results show that the RFPA can deliver a drain efficiency of 68.37 % at the output power of 40.79 dBm with power added efficiency of 66.94 %. The designed PA achieved a high gain between 13 dB to 17 dB from 0.5 GHz to 2.0 GHz of a frequency band. The matching circuits are realized on an FR-4 substrate to keep the cost as low as possible. A 10W GaN HEMT CGH40010 transistor from Cree has been used for this RFPA design.

A New Topology of Load Network for Class F RF Power Amplifiers

High efficiency RF power amplifiers are increasingly needed in modern mobile communication systems to reduce the battery size and power supply consumption. Class-F RF power amplifiers offer improved efficiency over the 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. 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. In this paper, a new load network for class F power amplifiers has been introduced and derived analytically. The proposed network consists of a parallel short circuited λ/8 stub, parallel open circuited λ/8 stub, and a T-section lumped-elementtransformer. The benefits of this topology include simplicity of design, controllable bandwidth, and harmonic tuning and impedance transformation at the same time. 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 simulated results haveindicated that the circuit gives adc-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.

Design of a High Linearity 6-GHz Class-F Radio Frequency Power Amplifier

In this study, a high linearity class-F RF power amplifier is introduced. It is designed to operate at a frequency of 6 GHz with a bandwidth of 400MHz. The amplifier mixes between the characteristics of conventional switch mode class-F and class B amplifiers. It is biased at very low quiescent power, thus it dissipates negligible DC power in the absence of RF excitation. This makes it suitable for handset applications. The amplifier is designed and tested on Microwave Office Environments. It showed linear input/output characteristics for an input RF power range of -20 to 5d Bm. The amplifier collector efficiency is 80%, which is greater than that of ideal class-B power amplifier. In addition, it is sensitive to amplify low level RF signals, therefore it needs no preamplifier.

Adjustable Load With Tracking Loop to Improve RF Rectifier Efficiency Under Variable RF Input Power Conditions

Terminating an RF rectifier with an optimum load resistance is important to maximize the efficiency of converting RF power to dc power. The optimum load resistance can also vary significantly as a function of RF input power. Therefore, an adjustable load circuit that tracks changes in RF power is required to maximize efficiency. As a way of implementing an adjustable load circuit that can provide a regulated output voltage to power a host system, a two-stage power-conversion circuit is proposed. The first stage is a dc-to-dc discontinuous mode converter that is controlled by an input loop to regulate the load impedance presented to the RF rectifier. The analysis, design, and experimental results of the first stage adjustable load circuit with a tracking loop are described. The load is connected to a 985-MHz 10-W GaN Class-F RF rectifier and results with the load circuit are compared to the optimum load.

High-efficiency class-F RF/microwave power amplifiers

This article provides a tutorial and review of recent developments in high-efficiency class F RF/ microwave PAs. The principles of class-F RF PAs are explained first. Recent progress in their theory and in design techniques is then presented. Different approaches of class-F PA designs are explained, and some examples of practical designs are illustrated. Finally, an attempt is made to discuss the future developments of class-F RF/microwave PAs.