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Wide bandwidth GaAs MESFET amplifierYan, Kai-tuan Kelvin 29 April 1992 (has links)
Graduation date: 1992
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Nonlinear System Identification and Analysis with Applications to Power Amplifier Modeling and Power Amplifier PredistortionRaich, Raviv 07 April 2004 (has links)
Power amplifiers (PAs) are important components of communication
systems and are inherently nonlinear. When a non-constant modulus
signal goes through a nonlinear PA, spectral regrowth (broadening)
appears in the PA output, which in turn causes adjacent channel
interference (ACI). Stringent limits on the ACI are imposed by
regulatory bodies, and thus the extent of the PA nonlinearity must
be controlled. PA linearization is often necessary to suppress
spectral regrowth, contain adjacent channel interference, and
reduce bit error rate (BER). This dissertation addresses the
following aspects of power amplifier research: modeling,
linearization, and spectral regrowth analysis.
We explore the passband and baseband PA input/output relationships
and show that they manifest differently when the PA exhibits
long-term, short-term, or no memory effects. The so-called
quasi-memoryless case is especially clarified. Four particular
nonlinear models with memory are further investigated. We provide
experimental results to support our analysis.
The benefits of using the orthogonal polynomials as opposed to the
conventional polynomials are explored, in the context of digital
baseband PA modeling and predistorter design. A closed-form
expression for the orthogonal polynomial basis is derived. We
demonstrate the improvement in numerical stability associated with
the use of orthogonal polynomials for predistortion.
Spectral analysis can help to evaluate the suitability of a given
PA for amplifying certain signals or to assist in predistortion
linearization algorithm design. With the orthogonal polynomials
that we derived, spectral analysis of the nonlinear PA becomes a
straightforward task. We carry out nonlinear spectral analysis
with digitally modulated signal as input. We demonstrate an
analytical approach for evaluating the power spectra of filtered
QPSK and OQPSK signals after nonlinear amplification.
Many communications devices are nonlinear and have a peak power or
peak amplitude constraint. In addition to possibly amplifying the
useful signal, the nonlinearity also generates distortions. We
focus on signal-to-noise-and-distortion ratio (SNDR) optimization
within the family of amplitude limited memoryless nonlinearities.
We obtain a link between the capacity of amplitude-limited
nonlinear channels with Gaussian noise to the SNDR.
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Hybrid Digital/RF Envelope Predistortion Linearization for High Power Amplifiers in Wireless Communication SystemsWoo, Wangmyong 27 April 2005 (has links)
Hybrid Digital/RF Envelope Predistortion Linearization for High Power Amplifiers in Wireless Communication Systems
Wangmyong Woo
151 Pages
Directed by Dr. J. Stevenson Kenney
The objective of this research is to implement a hybrid digital/RF envelope predistortion linearization system for high-power amplifiers used in wireless communication systems. It is well known that RF PAs have AM/AM (amplitude modulation) and AM/PM (phase modulation) nonlinear characteristics. Moreover, the distortion components generated by a PA are not constant, but vary as a function of many input conditions such as amplitude, signal bandwidth, self-heating, aging, etc. Memory effects in response to past inputs cause a hysteresis in the nonlinear transfer characteristics of a PA. This hysteresis, in turn, creates uncertainty in predictive linearization techniques. To cope with these nonlinear characteristics, distortion variability, and uncertainty in linearization, an adaptive digital predistortion technique, a hybrid digital/RF envelope predistortion technique, an analog-based RF envelope predistortion technique, and a combinational digital/analog predistortion technique have been developed.
A digital adaptation technique based on the error vector minimization of received PA output waveforms was developed. Also, an adaptive baseband-to-baseband test system for the characterization of RF PAs and for the validation of linearization algorithms was implemented in conjunction with the adaptation technique. To overcome disadvantages such as limited correction bandwidth and the need for a baseband input signal in digital predistortion, an adaptive, wideband RF envelope predistortion system was developed that incorporates a memoryless predistortion algorithm. This system is digitally controlled by a look-up table (LUT). Compared with conventional baseband digital approaches, this predistortion architecture has a correction bandwidth that is from 20 percent to 33 percent wider at the same clock speeds for third to fifth order IMDs and does not need a digital baseband input signal.
For more accurate predistortion linearization for PAs with memory effects, an RF envelope predistortion system has been developed that uses a combination of analog-based envelope predistortion (APD) working in conjunction with digital LUT-based adaptive envelope predistortion (DPD). The resulting combination considerably decreases the computational complexity of the digital system and significantly improves linearity and efficiency at high power levels.
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High efficiency switching CMOS power amplifiers for wireless communicationsLee, Ockgoo 13 November 2009 (has links)
High-efficiency performance is one of the most important requirements of power
amplifiers (PAs) for wireless applications. However, the design of highly efficient CMOS
PAs for watt-level applications is a challenging task. This dissertation focuses on the
development of the design method for highly efficient CMOS PAs to overcome the
fundamental difficulties presented by CMOS technology.
In this dissertation, the design method and analysis for a high-power and highefficiency
class-E CMOS PA with a fully integrated transformer have been presented.
This work is the first effort to set up a comprehensive design methodology for a fully
integrated class-E CMOS PA including effects of an integrated transformer, which is
very crucial for watt-level power applications. In addition, to improve efficiency of
cascode class-E CMOS PAs, a charging acceleration technique is developed. The method
accelerates a charging speed to turn off the common-gate device in the off-state, thus
reducing the power loss. To demonstrate the proposed cascode class-E PA, a prototype
CMOS PA was implemented in a 0.18-μm CMOS process. Measurements show an
improvement of approximately 6% in the power added efficiency. The proposed cascode
class-E PA structure is suitable for the design of high-efficiency class-E PAs while it
reduces the voltage stress across the device.
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A highly linear and efficient out-phasing transmitter for multi-band, multi-mode applicationsHur, Joonhoi 29 October 2010 (has links)
There have been many efforts to improve efficiency of transmitter while meeting stringent linearity requirement of modern communication system. Among the technology to enhance efficiency of linear transmitter, the out-phasing technologies, also called the linear amplification with nonlinear components (LINC), is considered as a promising technology. LINC has been studied long times, since it provides excellent linearity with high efficiency by allowing adopt high efficient switch-mode power amplifiers. However, The LINC transmitter has some technical challenges: linearity degradation due to amplitude and phase mismatches, efficiency degradation due to poor combining efficiency, and narrow frequency bandwidth due to output matching network of switching power amplifier.
In this thesis, some state-of-the-art techniques for solving the problems of LINC transmitters are presented. An unbalanced phase calibration technique compensates amplitude/phase mismatches between two parallel paths in the LINC system, and multi-level LINC (MLINC) and an uneven multi-level LINC (UMLINC) structure improve the overall power efficiency. And the reconfigurable Class-D switching PA enables multi-band operation with high efficiency and good linearity. With these techniques, the new multi-band out-phasing transmitter improves the efficiency without sacrificing the linearity performance.
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Quadrature predistortion using difference-frequency technique for base-station high-power amplifiersXiao, Mingxiang, January 2009 (has links)
Thesis (Ph. D.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 138-149). Also available in print.
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Parasitic-aware design and optimization of CMOS RF power amplifier /Choi, Kiyong. January 2003 (has links)
Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 146-149).
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Delta-Sigma Modulation Applied to Switching RF Power AmplifiersAndersson, Tobias, Wahlsten, Johan January 2007 (has links)
Background: The task of this thesis is to investigate the possibility of using non-linear high efficiency switching power amplifiers with spectrally efficient varying envelope modulation schemes and, if possible, further investigate such a solution on a high level. The thesis focuses on the theory necessary to understand the technical issues related to power amplifiers and the procedures behind simulating and measuring the characteristics of different power amplifier configurations. The thesis also covers basic theory behind Delta-Sigma-modulators. The theory is needed to draw conclusions about the feasibility of using a Delta-Sigma-modulator as input to a switching amplifier. Results: Using a Delta-Sigma-modulated input to a switching amplifier inherently degrades the performance, mainly because of poor coding efficiency and high switching activity. However, by merely using a switching amplifier as a mixer it is shown to be possible to transmit a non-constant envelope signal, with digital logic. The resulting circuit is, however, not an amplifier and it should not be seen as the final result. As already mentioned: the result lies in the investigation of a using Delta-Sigma-modulator as input to a switching amplifier. Conclusion: From this investigation we believe that the widely known technique: pulse width modulation (PWM), together with a tuned switching amplifier and some linearization technique, for example pre-distortion, is a better way to go. Much effort should be put in understanding the fundamental limits and possibilities of an efficient tuned switching power amplifier.
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RF power amplifiers and MEMS varactorsMahdavi, Sareh. January 2007 (has links)
This thesis is concerned with the design and implementation of radio frequency (RF) power amplifiers and micro-electromechanical systems---namely MEMS varactors. This is driven by the many wireless communication systems which are constantly moving towards increased integration, better signal quality, and longer battery life. / The power amplifier consumes most of the power in a receiver/transmitter system (transceiver), and its output signal is directly transmitted by the antenna without further modification. Thus, optimizing the PA for low power consumption, increased linearity, and compact integration is highly desirable. / Micro-electromechanical systems enable new levels of performance in radio-frequency integrated circuits, which are not readily available via conventional IC technologies. They are good candidates to replace lossy, low Q-factor off-chip components, which have traditionally been used to implement matching networks or output resonator tanks in class AB, class F, or class E power amplifiers. The MEMS technologies also make possible the use of new architectures, with the possibility of flexible re-configurability and tunability for multi-band and/or multi-standard applications. / The major effort of this thesis is focused on the design and fabrication of an RF frequency class AB power amplifier in the SiGe BiCMOS 5HP technology, with the capability of being tuned with external MEMS varactors. The latter necessitated the exploration of wide-tuning range MEMS variable capacitors, with prototypes designed and fabricated in the Metal-MUMPS process. / An attempt is made to integrate the power amplifier chip and the MEMS die in the same package to provide active tuning of the power amplifier matching network, in order to keep the efficiency of the PA constant for different input power levels and load conditions. / Detailed simulation and measurement results for all circuits and MEMS devices are reported and discussed.
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The development of an experimental, low profile, broadband travelling wave tube amplifier.Vassilopoulos, Nicolaos. January 1994 (has links)
An experimental, field replaceable travelling wave tube (TWT) with low profile, TEM
transitions has been developed with the aim of combining the cost advantages of field
replaceable TWTs with the bandwidth advantages of TEM transitions. Field replaceable
TWTs are cheaper because their periodic permanent magnet (PPM) stacks (which are
expensive) are easier to produce and can be reused. Standard TEM transitions have a
high profile and prevent TWTs from being plugged into PPM stacks. The stacks of
packaged TWTs are therefore built onto the tubes, using split ring magnets, before the
tubes are potted. Upon failure, such tubes are discarded together with their focusing,
coupling and cooling structures.
Two types of low profile, TEM transitions were investigated: a ring and a plug transition.
In the former, the helix was joined to a metal ring that was sandwiched between two
ceramic rings in the vacuum envelope. Due to its high shunt capacitance, this transition
was narrowband. In the plug transition, the helix was joined to a small metal plug in the
wall of a ceramic tube. Plug transitions with a return loss of better than 10 dB over an
octave were made but some technological difficulties were encountered. Metal/ceramic
joining with active solder is therefore discussed.
The development of graphite attenuators was attempted but graphite of high enough
resistivity to achieve the attenuation and matching required was not available. Thin film
attenuators were therefore used instead. Some good attenuators were made but the
molybdenum films were sensitive to processing conditions.
An empirical procedure was developed to magnetize PPM stacks to a wanted profile.
The stacks that were designed and built resulted in good beam focusing. TWT tests
were made using an automated test station that was built. Maximum RF gains and
output powers of 20 dB and 43 dBm respectively were measured.
The TWT design, construction and testing was a combination of materials science and
microwave work. Some simulations were used to solve electromagnetic problems but
much of the work was practical, involving trial and error and many measurements. / Thesis (Ph.D.)-University of Natal, Durban, 1994
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