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A new approach to dynamic range enhancementCheng, Fu-Sheng 10 November 2009 (has links)
This thesis evaluates a new approach for effectively increasing the dynamic range of optical fiber links for transporting RF signals. This new approach, called the Dynamic Range Enhancement Technique (DRET), is key to connecting remotely located microcell base station antenna sites to a centralized base station via optical fiber while maintaining a good dynamic range. This thesis examines the causes and characteristics of distortion introduced by the optical fiber link and describes and compares the performance of the DRET with other dynamic range enhancing techniques using computer simulation. In most instances, the DRET is shown to be superior both in reducing harmonic and intermodulation distortion compared to other dynamic range enhancement techniques. The DRET has several advantages over automatic gain control (AGC) including stability and the absence of parasitic modulation on weak signals caused by fading or transient high power signals. / Master of Science
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'n Studie van die elektroniese kompensasie van vervormings in kragnetwerke02 March 2015 (has links)
M.Ing. / Please refer to full text to view abstract
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A pipelined baseband digital predistortion architecture for RF amplifier linearizationXu, Xiangqing 30 May 1995 (has links)
This thesis describes the design of a baseband digital predistortion
architecture for radio frequency (RF) amplifier linearization. Existing amplifier
linearization techniques are first examined. The nonlinearity of an amplifier can
be characterized as amplitude-to-amplitude distortion and amplitude-to-phase
distortion. The distortion can be corrected by providing a predistorted driver
signal (both in amplitude and phase) to the amplifier. This counteracts the
nonlinearity of the amplifier so that the overall system is more linear. A
pipelined predistortion architecture is designed to allow fast processing speed,
and is capable of providing linearization for a bandwidth of 25 Mhz. The
simulation results show significant improvement in amplifier's performance
using predistortion technique. The system bandwidth versus cost is examined
by using commercially available components. / Graduation date: 1996
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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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Digital Circuit-Level Emulation of Transistor-Based Guitar Distortion EffectsOverton, William Ernest 13 April 2006 (has links)
The objective of this thesis was to model the Fuzz Face , a transistor-based guitar distortion effect, digitally at the circuit level, and explore how changes in the discrete analog components change the digital model. The circuit was first simulated using SPICE simulation software. Typically outputs and how they changed based on transistor gains were documented. A test circuit was then constructed in lab to determine true transistor gains. An analog Fuzz Face circuit was then constructed, and physical parameters were recorded. A digital model was then created using MATLAB. Capacitive filtering effects were found to be negligible in terms of the guitar signal and were not modeled. The transistors were modeled using the Ebers-Moll equations. A MATLAB algorithm was written to produce Fuzz Face type distortion given an input guitar signal. The algorithm used numerical techniques to solve the nonlinear equations and stored them in a look-up table. This table was used to process the input clips. The sound of the Fuzz Face was not perfectly modeled, but the equations were found to provide a reasonable approximation of the circuit. Further study is needed to determine a more complete modeling equation for the circuit.
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Understanding distortion in silicon-germanium transistors, and its application to RF circuitsSeth, Sachin 17 November 2009 (has links)
In an increasingly crowded frequency spectrum with strong interfering signals, the distortion performance, or the linearity, of RF circuits is key to their ability to reject strong intermodulation terms that can corrupt the weak but desired carrier signal. A standard figure-of-merit for small-signal linearity is the Input/Output Third Order Intercept Point (IIP3/OIP3), which represents the input/output power level at which the power of fundamental frequency (PFUND) become equal to that of the third-order intermodulation product (P3rd). Clearly, a higher IIP3 number yields improved linearity, and is highly desirable for many circuits.
The thesis will focus on describing the issues that can stem in telecommunication systems from these non-linearities. These non-linearities can be modeled by using a rigorous mathematical expansion based on the Volterra Series. The thesis will "demystify" the Volterra series so that it could be readily understood by the circuit designer, without over burdening him with too much mathematics. Using this series, the distortion performance of an amplifier will be quantified based on IIP3 metrics as described above. Having identified sources of non-linearities, and quantifying the effect of each non-linearity on total IIP3 of an amplifier, the thesis will focus on mitigating these non-linearity sources to increase the overall IIP3 of an amplifier. The techniques discussed to do this are based on both novel device design as well as novel circuit techniques. The amplifiers under discussion will all be SiGe based, due to their exemplary RF performances (comparable to III-V devices) at the fraction of the cost.
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Adaptive digital polynomial predistortion linearisation for RF power amplifiers : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Engineering in Electrical and Computer Engineering at the University of Canterbury, Christchurch, New Zealand /Giesbers, D. M. January 1900 (has links)
Thesis (M.E.)--University of Canterbury, 2008. / Typescript (photocopy). "August 2008." Includes bibliographical references (p. [123]-126). Also available via the World Wide Web.
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Power Spectrum Prediction of Amplified Dual-Band LTE-Advanced SignalsYang, Xianzhen 30 March 2018 (has links)
In wireless communication, the nonlinearity of a radio frequency (RF) power amplifier is an important issue for power amplifier designers. Since the nonlinearity is generated by the properties of physical components, it is hard to avoid it in producing power amplifiers. Power amplifier designers should know about the nonlinearity in order to compensate for it.
A two-tone test is a relatively widely used method to measure the nonlinearity of a power amplifier, which means the third order intercept point (IP3) can be measured from the two-tone test. Through the two-tone test, researchers have proposed some formulae to present what the amplified Code Division Multiple Access (CDMA) signal is like. They derived formulae in terms of output power, bandwidth, IP3, and IP5 to express the amplified CDMA signal and further to Orthogonal Frequency Division Multiplexing (OFDM) signals. With the development of wireless communication, researchers put their interest increasingly in Multiple Input Multiple Output (MIMO) systems. A formula expressing amplified dual two-tone signals has been proposed. In their research, they discussed what the expressions of intermodulation and cross modulation are and what their locations are.
In this research, dual band LTE-Advanced signals, whose modulation is OFDM are utilized, which means this research proposes a formula expression about the power spectrum of dual-band LTE-Advanced signals. Intermodulation and cross modulation caused by nonlinearity of power amplifiers are then specially discussed. This study will help RF designers to continuously compensate for them.
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Distortion analysis of CMOS analog integrated circuits operating in the moderate inversion region and implications for RF applications /Toole, William January 1900 (has links)
Thesis (Ph. D.)--Carleton University, 2004. / Includes bibliographical references (p. 217-223). Also available in electronic format on the Internet.
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