High-Frequency Power Amplitude Modulators with Class-E Tuned Amplifiers, Journal of Telecommunications and Information Technology, 2008, nr 4

A high-frequency power amplifier used in a drain amplitude modulator must have linear dependence of output HF voltage Vo versus its supply voltage VDD. This condition essential for obtaining low-level envelope distortions is met by a theoretical class-E amplifier with a linear shunt capacitance of the switch. In this paper the influence of non-linear output capacitance of the transistor in the class-E amplifier on its Vo(VDD) characteristic is analyzed using PSPICE simulations of the amplifiers operating at frequencies 0.5 MHz, 5 MHz and 7 MHz. These simulations have proven that distortions of theVo(VDD) characteristic caused by non-linear output capacitance of the transistor are only slight for all analyzed amplifiers, even for the 7 MHz amplifier without the external (linear) shunt capacitance. In contrast, the decrease of power efficiency of the class-E amplifier resulting from this effect can be significant even by 40%

High Efficiency Class E Microwave Frequency Multipliers

A novel design methodology for the successful implementation of high efficiency class E frequency multipliers is presented in this work. An innovative class E configuration is proposed for a frequency tripler that provides an advantage over the conventional designs, by allowing a 50 %duty cycle drive with a realisable load for 100 %DC-to-RF efficiency operation. A novel quantitative analysis of class E networks is developed that aids in the rapid yet accurate assessment of circuit performance. The first-order analysis provides an intuitive evaluation of class E operation and harmonic content of the switch waveforms. The analysis is shown to be applicable to both class E amplifiers and multipliers, providing closed-form equations for an intelligent first design. The proposed class E tripler configuration is evaluated using this technique and is shown to be a practically viable solution for achieving high DC-to-RF efficiency. Techniques involved in the design and implementation of the novel frequency tripler are investigated, and three microstrip circuits are presented that provide high drain efficiency, high unwanted harmonic rejection and low DC power consumption. Innovative design of the input matching circuit that exploits the nonlinear input capacitance of the device, and the output matching circuit that simultaneously provides appropriate harmonic terminations and unwanted harmonic rejection, ensure a simultaneously high achievable conversion gain and DC-to-RF efficiency. Practical demonstration of the three novel circuits display the highest reported DC-to-RF efficiency and conversion gain for m~crowave frequency triplers to date. Trade-oITs between circ.uit complexity,size and simultaneously achievable high efficiency and high conversion gain are identified and elucidated with the three novel designs

Applications of the genetic algorithm optimisation approach in the design of high efficiency microwave class E power amplifiers

In this thesis Genetic Algorithm Optimisation Methods (GA) is studied and for the first time used to design high efficiency microwave class E power amplifiers (PAs) and associated load patch antennas. The difficulties of designing high efficiency PAs is that power transistors are highly non linear and classical design techniques only work for resistive loads. There are currently no high efficient and accurate procedures for design high efficiency PAs. To achieve simplified and accurate design procedure, GA and new design quadratic equations are introduced and applied. The performance analysis is based on linear switch models and non linear circuitry push-pull methods. The results of the analytical calculations and experimental verification showed that the power added efficiency (PAE) of the PAs mainly depend on the losses of the active device itself and are nearly independent on the losses of its harmonic networks. Hence, it has been proven that the cheap material PCB FR4 can be used to design high efficiency class E PAs and it also shown that low Q factor networks have only a minor effect on efficiency, allowing a wide bandwidth to be obtained. In additional, a new procedure for designing class E PAs is introduced and applied. The active device (ATF 34143) is used. Good agreement was obtained between predicted analyses and the simulation results (from Microwave Office (AWR) and Agilent ADS software). For the practical realization, class E PAs were fabricated and tested using PCB FR4. The practical results validate computer simulations and the PAE of the class E PAs are more than 71% and Gain is over 3.8 dB when input power (Pin) is equal to 14 dBm at 2 GHz

Simple and Efficient Transcutaneous Inductive Micro-System Device Based on ASK Modulation at 6.78 MHz ISM Band

This paper deals with designing a simple and efficient simultaneous inductive power and data transmission for transcutaneous Micro-system based on ASK modulation at 6,78 MHz industrial, scientific, and medical (ISM) band to avoid the tissue damage. The modified ASK modulator and inductive coupling link driven by efficient Class-E power amplifier with 94,5% efficiency and the coupling link of up to 78,29% of efficiency are introduced to transmit 500 Kbit/s of data with modulation index 12,5%, modulation rate 7,37%. The proposed design is simple, easy to implement and able to power the bio-implantable devices with DC V up to 5 V. The mathematical model is given and the system is designed and validated by professional OrCADPsPice 16,6 environment simulation using a standard AMS 0,35 μm MOS technology. In addition, for real-time simulation, the electronic workbench MULISIM 11 has been used to simulate the class-E power amplifier switching. This design is useful for cochlear implants, retinal implants and implantable micro-system stimulator

Class-E Power Amplifiers in Modern RF Transmitters

Power amplifiers have been playing a vital role in most wireless communication systems. In order to improve efficiency of wireless systems, advanced transmitter architectures, such as Doherty amplifiers, outphasing amplifiers, supply voltage modulation techniques are widely used. The goal of this work is to develop novel techniques for building load modulation transmitters based on class-E power amplifiers. The first contribution is an analytical model for derivation load network parameters. The proposed model derives the parameters for both the peak and back-off power levels providing high efficiency. The proposed model demonstrates, that class-E PA with shunt capacitance and shunt filter is capable of providing high drain efficiency for back-off output power levels. The second contribution is a design of a wideband class-E power amplifier (PA) with shunt capacitance and shunt filter. The broadband operation has been achieved by application of the double reactance compensation technique. Simulated and experimental results are presented. The performance of the fabricated PA is compared with existing wideband PAs. The third contribution is application of the proposed technique to outphasing PA design. The designed outphasing PA was optimized, fabricated and tested. A possibility to extend the operational bandwidth of the PA is considered. Also the application of the proposed technique to Doherty PA design is demonstrated. The fourth contribution is linearization of outphasing PA. Firstly, an analytical model describing the nonlinearity of nonisolated combiners under amplitude imbalance is presented. Secondly, a novel phase-only predistortion technique for class-E outphasing PAs is proposed. Thirdly, linearization of the fabricated outphasing PA based on memory polynomial model is demonstrated using a 64QAM OFDM modulated signal with 20 MHz bandwidth. Overall, this work provides novel techniques for load modulation transmitter design based on class-E power amplifiers with shunt capacitance and shunt filter