The Switched Mode Power Amplifiers

Non

Radio Frequency Interference /RFI/ design guide for aerospace communications systems

Radio frequency interference design guide for aerospace communications system

A very low distortion high efficiency class-F power amplifier at 900 MHz.

This paper presents a novel class - F power amplifier for mobile applications in which with a proper harmonic tuning structure the need f or an extra fil tering section is eliminated . A class - F power a mplifier employing a GaN HEMT device has been designed, fabricated and measured at 900 MHz . The fabricated circuit achieves a n excel lent harmonic - suppression level and the t otal h armonic distortion is around 1.2% . It overcomes the narrow band performance of class - F power amplifier s, giving more than 70% efficiency over a 100 MHz bandwidth . Experimental results show that the amplifier is able to deliver 38.5 dBm output power while achieving the state - of - the - art PAE of 8 0.5 % with a peak drain eff iciency of 8 4 % , and a power gain of 13.6 dB for an input power of 25 dBm . A good agreement between measurement and simulation results is observed for the proposed structure.Peer ReviewedPostprint (published version

Hysteresis and oscillation in high-efficiency power amplifiers

Hysteresis in power amplifiers (PAs) is investigated in detail with the aid of an efficient analysis method, compatible with commercial harmonic balance. Suppressing the input source and using, instead, an outer-tier auxiliary generator, together with the Norton equivalent of the input network, analysis difficulties associated with turning points are avoided. The turning-point locus in the plane defined by any two relevant analysis parameters is obtained in a straightforward manner using a geometrical condition. The hysteresis phenomenon is demonstrated to be due to a nonlinear resonance of the device input capacitance under near optimum matching conditions. When increasing the drain bias voltage, some points of the locus degenerate into a large-signal oscillation that cannot be detected with a stability analysis of the dc solution. In driven conditions, the oscillation will be extinguished either through synchronization or inverse Hopf bifurcations in the upper section of the multivalued curves. For an efficient stability analysis, the outer-tier method will be applied in combination with pole-zero identification and Hopf-bifurcation detection. Departing from the detected oscillation, a slight variation of the input network will be carried out so as to obtain a high-efficiency oscillator able to start up from the noise level. All the tests have been carried out in a Class-E GaN PA with measured 86.8% power-added efficiency and 12.4-W output power at 0.9 GHz.This work was supported by the Spanish Ministry of Economy and Competitiveness (MINECO) under Project TEC2014-60283-C3-1-R and Project TEC2014-58341-C4-1-R, with FEDER co-funding, the Parliament of Cantabria (12.JP02.64069) and by the Predoctoral Fellowship for Researchers in Training of the University of Cantabria and the Regional Ministry of Education of the Government of Cantabria

Contributing to Second Harmonic Manipulated Continuum Mode Power Amplifiers and On-Chip Flux Concentrators

The current cellular network consumes a staggering 100 TWh of energy every year. In the coming years, millions of devices will be added to the existing network to realize the Internet of Things (IoT), further increasing its power consumption. An RF power amplifier typically consumes a large proportion of the DC power in a wireless transceiver, improving its efficiency has the largest impact on the overall system. Additionally, amplifiers need to demonstrate high linearity and bandwidth to adhere to constraints imposed by wireless standards and to reduce the number of amplifiers required as an amplifier with a broader bandwidth can potentially replace several narrowband amplifiers. A typical approach to improve efficiency is to present an appropriate load at the harmonics generated by the transistor. Recently proposed continuous modes based on harmonic manipulation, such as class B/J continuum, continuous class F (CCF) and continuous class F-1 (CCF-1), have shown the capability of achieving counteracting requirements viz., high efficiency, high linearity, and broad bandwidth (with a fractional bandwidth greater than 30%). In these classes of amplifiers, the second harmonic is manipulated by placing a reactive second harmonic load and the reactive component of the fundamental load is adjusted while keeping a fixed resistive component of the fundamental load. The first contribution of this work is to investigate the reason for amplifiers designed in classes B/J continuum and CCF to achieve high efficiency at back-off and 1dB compression. In this thesis, we demonstrate that the variation of the phase of the current through the non-linear intrinsic capacitances due to the variation of the phase in the continuum of drain voltage waveforms in Class B/J/J* continuum leads to either a reduction or enhancement of intrinsic drain current. Consequently, a subset of voltage waveforms of the class B/J/J* continuum can be used to design amplifiers with higher P1dB, and efficiency at P1dB than in Class B. A simple choice of this subset is demonstrated with a 2.6GHz Class B/J/J* amplifier, achieving a P1dB of 38.1dBm and PAE at P1dB of 54.7%, the highest output power and efficiency at P1dB amongst narrowband linear amplifiers using the CGH40010 reported to date, at a comparable peak PAE of 72%. Secondly, we propose a new formulation for high-efficiency modes of power amplifiers in which both the in-phase and out-of-phase components of the second harmonic of the current are varied, in addition to the second harmonic component of the voltage. A reduction of the in-phase component of the second harmonic of current allows reduction of the phase difference between the voltage and current waveforms, thereby increasing the power factor and efficiency. Our proposed waveforms offer a continuous design space between class B/J continuum and continuous F-1 achieving an efficiency of up to 91% in theory, but over a wider set of load impedances than continuous class F-1. These waveforms require a short at third and higher harmonic impedances, which are easier to achieve at a higher frequency. The load impedances at the second harmonic are reactive and can be of any value between -j∞ and j∞, easing the amplifier design. A trade-off between linearity and efficiency exists in the newly proposed broadband design space, but we demonstrate inherent broadband capability. The fabricated narrowband amplifier using a GaN HEMT CGH40010F demonstrates 75.9% PAE and 42.2 dBm output power at 2.6 GHz, demonstrating a comparable frequency weighted efficiency for this device to that reported in the literature. IoT devices may be deployed in critical applications such as radar or 5G transceivers of an autonomous vehicle and hence need to operate free of failure. Monitoring the drain current of the RF GaN MMIC would allow to optimize the device performance and protect it from surges in its supply current. Galvanic current sensors rely on the magnetic field generated by the current as a non-invasive method of current sensing. In this thesis, our third major contribution is a planar on-chip magnetic flux concentrator, is enhance the magnetic field at the current sensor, thereby improving the current detection capability of a current sensor. Our layout utilizes a discontinuity in a magnetic via, resulting in penetration of the magnetic field into the substrate. The proposed concentrator has a magnetic gain x1.8 in comparison to air. The permeability of the magnetic core required is 500, much lower than that reported in off-chip concentrators, resulting in a significant easing of the specifications of the material properties of the core. Additionally, we explore a novel three-dimensional spiral-shaped magnetic flux concentrator. It is predicted via simulations that this geometry becomes a necessity to enhance the magnetic field for increased form factor as the magnetic field from a single planar concentrator deteriorates as its size increases

Techniques for Wideband All Digital Polar Transmission

abstract: Modern Communication systems are progressively moving towards all-digital transmitters (ADTs) due to their high efficiency and potentially large frequency range. While significant work has been done on individual blocks within the ADT, there are few to no full systems designs at this point in time. The goal of this work is to provide a set of multiple novel block architectures which will allow for greater cohesion between the various ADT blocks. Furthermore, the design of these architectures are expected to focus on the practicalities of system design, such as regulatory compliance, which here to date has largely been neglected by the academic community. Amongst these techniques are a novel upconverted phase modulation, polyphase harmonic cancellation, and process voltage and temperature (PVT) invariant Delta Sigma phase interpolation. It will be shown in this work that the implementation of the aforementioned architectures allows ADTs to be designed with state of the art size, power, and accuracy levels, all while maintaining PVT insensitivity. Due to the significant performance enhancement over previously published works, this work presents the first feasible ADT architecture suitable for widespread commercial deployment.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201

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