M. Tech. (Chemical Engineering, Faculty of Engineering and Technology), Vaal University of Technology / Amplitude modulation is not commonly associated with effective amplifying. This work focuses on implementing amplitude modulation into a high efficiency Class E amplifier. Different types of amplifiers are compared with each other, to show the advantages of using a Class E amplifier. The theory of the Class E amplifier is dealt with in detail. A harmonic filter is designed for the amplifier to make it radio spectrum friendly. The modulation process is implemented with the aid of a transformer into the Class E amplifier. The advantage of this is that the transformer serves both as a radio frequency choke for the Class E circuit as well as a modulator. The implementation of the amplitude modulation into the high efficient Class E circuit was successful. The final Class E circuit had superb efficiency, the harmonic filter showed good harmonic attenuation and the modulation process had low distortion. All this resulted in a fine low power AM transmitter.

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 68-70). Also available on the World Wide Web.

Thesis (M. App. Sc.)--Carleton University, 2003. / Includes bibliographical references (p. 99-102). Also available in electronic format on the Internet.

Thesis (M. App. Sc.)--Carleton University, 2004. / Includes bibliographical references (p. 84-93). Also available in electronic format on the Internet.

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2011 / Modern technologies have led to extensive digital music reproduction and distribution. It is fitting then that digital audio be amplified directly from its source rather than being converted to an analogue waveform before amplification. The benefits of using a digital controller for audio processing include being able to easily reconfigure the system and to add additional functions at a later stage.Digital audio is primarily stored as Pulse Code Modulation (PCM) while Pulse Width Modulation (PWM) is the most popular scheme used to drive a class-D amplifier. The class-D amplifier is selected in many applications due to its very high energy efficiency. Conventional PCM to PWM conversion is inherently nonlinear. Various interpolation schemes are presented in this research project which help to address the nonlinearity.Digitally generated PWM has a limited resolution which is constrained by the system clock. This thesis presents noise shaping techniques which increase the effective resolution of the PWM process without having to use an excessively high system clock. Noise shaping allows a low resolution modulator to be used to reproduce high resolution audio.

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2016. / In all radio frequency (RF) electronic communication systems, power amplifiers (PAs) are used to generate the final transmitted signal. Specifically, these PAs are used to increase the output power of the transmitted signal. The PA accomplishes this by converting the applied direct current (DC) power to the PA into RF power, while being driven by a RF input signal. The portion of DC power that is not converted into RF power is dissipated as heat. The power conversion mechanism that takes place in a PA is described by the power conversion efficiency (PE) and the power added efficiency (PAE). A CubeSat is a small satellite in the shape of a 10 × 10 × 10 cm cube, weighing less than 1 kg and contains a RF electronic communication system which allows communication with the satellite. A CubeSat requires a PA with high PE in order to increase the lifetime of the on-board battery, facilitate thermal management on-board the satellite, increase system reliability, and reduce the size and manufacturing cost of the satellite. To maximize the theoretical PE of a RF PA, several design techniques and classes of operation were investigated, the basis of which lies in the fulfilment of the necessary and sufficient conditions for a maximum PE. A PA, which uses the Class-F-1 (inverse Class-F) mode of operation, fulfils the necessary and sufficient conditions for a maximum theoretical PE, and therefore presents itself as a good option for a high efficiency PA. This thesis presents the design of a Class-F-1 PA, using the Cree CGH40010F GaN power active device. An optimum output matching network is used to terminate the drain of the GaN power active device with the required load impedances at the fundamental, 2nd and 3rd harmonic frequencies of operation. The designed PA delivers a maximum PE of 95 % at an operating frequency of 2.2 GHz, a maximum PAE of 82 % at an operating frequency of 2.2 GHz and a maximum output power of 40.6 dBm at an operating frequency of 2.2 GHz.

No description available.

published_or_final_version / Electrical Engineering / Master / Master of Science in Engineering

published_or_final_version / Electrical Engineering / Master / Master of Philosophy

published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy