Analysis and Design of Outphasing Transmitter Using Class-E Power Amplifiers With Shunt Capacitances and Shunt Filters

In this paper, a novel outphasing power amplifier (PA) based on class-E amplifiers with shunt capacitances and shunt filters is proposed. The new design provides high drain efficiency for both peak and back-off power levels. A mathematical model for the class-E power amplifier with shunt capacitance and shunt filter is presented. The proposed model enables derivation of load circuit parameters that provide optimum drain efficiency for the peak and back-off power levels using closed form mathematical expressions. Based on this model, an outphasing power amplifier is designed and subsequently implemented using microstrip transmission lines and a GaN HEMT devices. The fabricated power amplifier prototype is optimized for 2.14 GHz and provides drain efficiency of over 60% for back-off power levels up to 8.5 dB. The amplifier demonstrates a 44.3% drain efficiency for 64QAM OFDM modulated signal with 20 MHz bandwidth. Adjacent channel leakage ratio (ACLR) of −39.5 dB and error vector magnitude (EVM) of 0.9 % were achieved after the application of a memory polynomial linearization algorithm

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

Class E/F switching power amplifiers

The present invention discloses a new family of switching amplifier classes called class E/F amplifiers. These amplifiers are generally characterized by their use of the zero-voltage-switching (ZVS) phase correction technique to eliminate of the loss normally associated with the inherent capacitance of the switching device as utilized in class-E amplifiers, together with a load network for improved voltage and current wave-shaping by presenting class-F.sup.-1 impedances at selected overtones and class-E impedances at the remaining overtones. The present invention discloses a several topologies and specific circuit implementations for achieving such performance

Novel techniques for improving the performance of MESFET power amplifiers.

This thesis describes the research activities that have been investigated for improving the 3rd order intermodulation distortion products (IM3) and power added efficiency (PAE) and bandwidth performance of microwave GaAs MESFET power amplifiers. Two novel circuit techniques, one for improving the 3dB bandwidth performance and the other for improving the IM3 and PAE performance, were proposed and verified through simulation and practical measurements. The technique of including lumped elements matching networks within the package encapsulation (Close-to-Chip lumped element matching) of a 2GHz MESFET device is described for the first time. Simulation results showed that the amplifier using this technique had a 3dB bandwidth 3 times wider than the amplifier with Off-Chip distributed element matching. The linearity and efficiency performance of a 2GHz MESFET was improved significantly by presenting a difference frequency shunt short-circuit termination across the drain terminal. A 16dB reduction in IM3 and an improvement of 4% in PAE performance was measured on the bench. Success with this technique was further demonstrated with digitally modulated signals

The Switched Mode Power Amplifiers

Non

Using MEMS in class D amplifiers for standard GSM carrier

The equivalent circuit of MEMS capacitive switches can be used to analyze a class D power amplifier, operated by a power supply of 3.7V. The system is intended for GSM audio frequency to produce an output power of (0.5-1.0) mW at a load output impedance of (8-10) Q. The system gain must be greater than 33 dBm and the estimated loss (0.5-1) dB. A model for the power amplifier using MEMS passive devices has been developed. The model helps to determine the design parameters that affect the performance and reliability of the system that operate an RF transceiver. The optimization of the amplifier and the MEMS capacitor switching devices and how to integrate the system, will also be discussed. The design and the equivalent circuit were simulated using a PSpice model