Dissertations / Theses on the topic 'Broadband frequency'
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1
Chou, Thomas Clayton. "Broadband frequency-independent beamforming." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11854.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.Includes bibliographical references (p. 103-105).
by Thomas Clayton Chou.
M.S.
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雷靜 and Jing Lei. "Frequency synchronization methods for digital broadband receivers." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B31244427.
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Pamuk, Gokhan. "Design And Realization Of Broadband Instantaneous Frequency Discriminator." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/3/12612044/index.pdf.
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In this thesis, RF sections of a multi tier instantaneous frequency measurement (IFM) receiver which can operate in 2 &ndash18 GHz frequency band is designed, simulated and partially realized. The designed structure uses one coarse tier, three medium tiers and one fine tier for frequency discrimination. A novel reflective phase shifting technique is developed which enables the design of very wideband phase shifters using stepped cascaded transmission lines. Compared to the classical phase shifters using coupled transmission lines, the new approach came out to be much easier to design and fabricate with much better responses. This phase shifting technique is used in coarse and medium tiers. In fine frequency measurement tier, I/Q discriminator approach is used because reflective phase shifters would necessitate unacceptably long delay lines. Two I/Q discriminators are designed and fabricated using Lange directional couplers that operate in 2-6 GHz and 6-18 GHz, resulting in satisfactory response. Additionally, 6 GHz HP and 6 GHz LP distributed filters are designed and fabricated to be used for these I/Q discriminators in fine tier. In order to eliminate possible ambiguities in coarse tier, a distributed element LP-HP diplexer with 10 GHz crossover frequency is designed and fabricated successfully to be used for splitting the frequency spectrum into 2-10 GHz and 10-18 GHz to ease the design and realization problems. Three power dividers operating in the ranges 2-18 GHz, 2-6 GHz and 6-18 GHz are designed for splitting incoming signals into different branches. All of these dividers are also fabricated with satisfactory response. The fabricated components are all compact and highly reproducible. The designed IFM can tolerate 48 degrees phase margin for resolving ambiguity in the tiers while special precautions are taken in fine tier to help ambiguity resolving process also. The resulting IFM provides a frequency resolution below 1 MHz in case of using an 8-bit sampler with a frequency accuracy of 0.28 MHz rms for 0 dB input SNR and 20 MHz video bandwidth.
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To, Chau B. "Real Frequency Parametric Approach to Broadband Matching Problems." Thesis, California State University, Long Beach, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10638732.
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The purpose of this project is to study the real frequency parametric approach and to implement it in MATLAB as a CAD matching network synthesizer. This approach uses the parametric presentation of Brune function for modeling the real part of the immittance function of the lossless equalizer, which improves the computational time and numerical stability. The parametric approach inherits all the merits of the former real frequency direct computational technique; therefore, it is able to provide optimized solutions for double matching problems as well as the single matching problems.
The parametric approach is applied to examples presented in this project including a double matching problem and a single matching problem. In addition, different topologies of the equalizer are presented in each matching problem. To compare the behavior and the efficiency of each matching network, wideband S-parameter simulation for each scenario is generated by Agilent Design System (ADS) software.
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Ward, Darren Brett, and db_ward@hotmail com. "Theory and application of broadband frequency invariant beamforming." The Australian National University. Faculty of Engineering and Information Technology, 1996. http://thesis.anu.edu.au./public/adt-ANU20050418.112459.
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In many engineering applications, including radar, sonar, communications and seismology, the direction of impinging signal wavefronts can be used to discriminate between competing sources. Often these source signals cover a wide bandwidth and conventional narrowband beamforming techniques are ineffective, since spatial resolution varies significantly across the band. In this thesis we consider the problem of beamforming for broadband signals, primarily when the spatial response remains constant as a function of frequency. This is called a frequency invariant beamformer (FIB).¶
Rather than applying the numerical technique of multi-parameter optimisation to solve for the beamformer parameters, we attempt to address the fundamental nature of the FIB problem. The general philosophy is to use a theoretical continuous sensor to derive relationships between a desired FI beampattern and the required signal processing structure. Beamforming using an array of discrete sensors can then be formulated as an approximation problem. This approach reveals a natural structure to the FIB which is otherwise buried in a numerical optimisation procedure.¶
Measured results from a microphone array are presented to verify that the simple FIB structure can be successfully implemented. We then consider imposing broadband pattern nulls in the FI beampattern, and show that (i) it is possible to impose an exact null which is present over all frequencies, and (ii) it is possible to calculate a priori how many constraints are required to achieve a null of a given depth in a FIB. We also show that the FIB can be applied to the problem of broadband direction of arrival (DOA) estimation and provides computational advantages over other broadband DOA estimators.¶
Through the theoretical continuous sensor approach, we show that the FIB theory can be generalised to the problem of designing a general broadband beamformer (GBB) which realizes a broadband angle-versus-frequency beampattern specification. Coupled with a technique for radial beampattern transformation, the GBB can be applied to a wide class of problems covering both nearfield beamforming (in which the shape of the impinging wavefront must be considered and farfield beamforming (which is simplified by the assumption of planar wavefronts) for a broadband beampattern specified over both angle and frequency.
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Kongara, Gayathri. "Space-Frequency Equalization in Broadband Single Carrier Systems." Thesis, University of Canterbury. Electrical and Computer engineering, 2009. http://hdl.handle.net/10092/4421.
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Broadband wireless access systems can be used to deliver a variety of high data
rate applications and services. Many of the channels being considered for such
applications exhibit multipath propagation coupled with large delay spreads. Cur-
rently, orthogonal frequency division multiplexing is employed in these channels
to compensate the effect of dispersion. Single carrier (SC) modulation in conjunc-
tion with frequency-domain equalization (FDE) at the receiver has been shown to
be a practical alternate solution as it has lower peak to average power ratio and is
less sensitive to frequency offsets and phase noise compared to OFDM. The effect
of multipath propagation increases with increasing data rate for SC systems. This
leads to larger inter-symbol-interference (ISI) spans. In addition the achievable ca-
pacity of SC-broadband systems depends on their ability to accommodate multiple
signal transmissions in the same frequency band, which results in co-channel inter-
ference (CCI) when detecting the desired data stream. The effects of CCI and ISI
are more pronounced at high data rates. The objective of this research is to investi-
gate and a develop low-complexity frequency domain receiver architectures capable
of suppressing both CCI and ISI and employing practical channel estimation.
In this thesis, a linear and a non-linear receiver architecture are developed in the
frequency domain for use in highly dispersive channels employing multiple input
multiple output (MIMO) antennas. The linear receiver consists of parallel branches
each corresponding to a transmit data stream and implements linear equalization
and demodulation. Frequency domain joint CCI mitigation and ISI equalization is
implemented based on estimated channel parameters and is called space-frequency
Broadband wireless access systems can be used to deliver a variety of high data
rate applications and services. Many of the channels being considered for such
applications exhibit multipath propagation coupled with large delay spreads. Cur-
rently, orthogonal frequency division multiplexing is employed in these channels
to compensate the effect of dispersion. Single carrier (SC) modulation in conjunc-
tion with frequency-domain equalization (FDE) at the receiver has been shown to
be a practical alternate solution as it has lower peak to average power ratio and is
less sensitive to frequency offsets and phase noise compared to OFDM. The effect
of multipath propagation increases with increasing data rate for SC systems. This
leads to larger inter-symbol-interference (ISI) spans. In addition the achievable ca-
pacity of SC-broadband systems depends on their ability to accommodate multiple
signal transmissions in the same frequency band, which results in co-channel inter-
ference (CCI) when detecting the desired data stream. The effects of CCI and ISI
are more pronounced at high data rates. The objective of this research is to investi-
gate and a develop low-complexity frequency domain receiver architectures capable
of suppressing both CCI and ISI and employing practical channel estimation.
In this thesis, a linear and a non-linear receiver architecture are developed in the
frequency domain for use in highly dispersive channels employing multiple input
multiple output (MIMO) antennas. The linear receiver consists of parallel branches
each corresponding to a transmit data stream and implements linear equalization
and demodulation. Frequency domain joint CCI mitigation and ISI equalization is
implemented based on estimated channel parameters and is called space-frequency
7
Thiem, Keem B. "Design of broadband wire antennas for frequency hopping applications." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA267405.
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Zhu, Yu. "Frequency domain equalization for single carrier broadband wireless communications /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?ECED%202007%20ZHUY.
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Zhang, Jin. "Fixed broadband wireless access systems at millimeter wave frequency." Thesis, University of South Wales, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436363.
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Shah, Veeral S. (Veeral Sanjay) 1978. "Timing and frequency synchronization in OFDM broadband wireless systems." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/86850.
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Hill, Samuel Joseph. "Time-frequency localisation of defects using broadband pulsed arrays." Thesis, University of Warwick, 2014. http://wrap.warwick.ac.uk/63771/.
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The spatial periodicity of an array of emitters with an alternating polarity structure is utilised to generate a wavefront with a range of interesting properties. This wavefront is generated by simultaneously exciting the elements with a pulse with carefully selected broadband characteristics. The creation of these waves leads to a broadband interference effect that causes the wavefront to cover a large range of solid angles. More interestingly, however, is the continuous variation of the frequency of the wavefront as a function of angle. Whilst this pulsed array system demonstrates many interesting phenomena, it can also be applied to practical scenarios within the field of non-destructive testing. As the generated wavefront propagates through the sample, it will be scattered by discontinuities that may be present in the sample. This scattered wave will have a unique time of flight and frequency, and this information can be used to locate the position of defects. Due to the frequency variation of the wavefront, the angular position of the defect can be calculated from the frequency of the scattered wave. The radial position of the scatterer can be estimated using the time of flight of the wave. This approach has some advantages over the phased array techniques, which are currently utilised within the field of ultrasonic inspection. Whilst phased array techniques are versatile and can control the generated ultrasonic beam, they require complicated electronics and beam-forming algorithms to achieve this. This requirement is avoided with the pulsed array, as all of the array elements are activated simultaneously. Also, as the time-frequency characteristics of the scattered wave maps directly to the polar co-ordinates, only a single measurement is needed to locate a defect. This is in contrast to other ultrasonic methods that only utilise the time of flight information of the scattered wave, and hence multiple measurements are needed to localise a defect.
12
Jain, Nidhi. "Single carrier frequency domain equalization for broadband wireless communications." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/5996.
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Thesis (M.S.)--University of Missouri-Columbia, 2007.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on November 13, 2008) Includes bibliographical references.
13
Miyake, Hiroe. "Frequency-Dependent Source Heterogeneities for Broadband Ground Motion Simulation." 京都大学 (Kyoto University), 2003. http://hdl.handle.net/2433/149078.
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Kyoto University (京都大学)0048
新制・課程博士
博士(理学)
甲第9956号
理博第2617号
新制||理||1333(附属図書館)
UT51-2003-H377
京都大学大学院理学研究科地球惑星科学専攻
(主査)教授 入倉 孝次郎, 教授 Mori James J., 教授 岡田 篤正
学位規則第4条第1項該当
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Harrison, S. M. "Radio frequency design issues for a broadband local area network." Thesis, University of Sussex, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375840.
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Rose, C. S. "Ultra-broadband frequency generation in a cavity confined Raman medium." Thesis, University of Salford, 2013. http://usir.salford.ac.uk/31828/.
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Throughout the past few decades, science has progressed towards the ability to probe many extremely fast processes and a large amount of research has been aimed at the area of few-femtosecond pulse generation. This thesis describes the generation of coherent broadband radiation through two-colour pumping of molecular hydrogen confined to a unidirectional ring cavity, and the subsequent synthesis of high peak power and few-femtosecond pulses. A set of normalised semi-classical field equations are derived in Bloch form describing the process of ultra-broadband multi-frequency Raman generation or UMRG, and a 3-wave gain suppression analysis is derived from a subset of the plane wave UMRG field equations which describes gain suppression within the ring cavity in terms of both medium and cavity parameters. The gain suppression analysis is further generalised to include finite levels of linear two-photon frequency detuning of the pump beams. Simulations of the plane wave ultra-broadband multi-frequency Raman (UMRG) equations show that a broad frequency spectrum of mutually coherent sideband can be generated. The inverse Fourier transform of spectra generated in this way yields a train of high power near Fourier limited pulses in the time domain which can range from a few-femtoseconds in duration to tens of attoseconds with repetition rates equal to the Raman transition frequency. Pulses synthesised in this way are limited only by the level of medium dispersion, the reflection bandwidth of the chosen coupling mirror and the chosen Raman medium. Simulations of the transverse UMRG equations within the ring cavity geometry have shown ring cavity enhanced UMRG to be resilient to transverse effects such as finite beam width, beam diffraction and the transverse beam separation of the applied pump beams.
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Koh, Choo Leng. "Broadband adaptive beamforming with low complexity and frequency invariant response." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/69593/.
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This thesis proposes different methods to reduce the computational complexity as well as increasing the adaptation rate of adaptive broadband beamformers. This is performed exemplarily for the generalised sidelobe canceller (GSC) structure. The GSC is an alternative implementation of the linearly constrained minimum variance beamformer, which can utilise well-known adaptive filtering algorithms, such as the least mean square (LMS) or the recursive least squares (RLS) to perform unconstrained adaptive optimisation. A direct DFT implementation, by which broadband signals are decomposed into frequency bins and processed by independent narrowband beamforming algorithms, is thought to be computationally optimum. However, this setup fail to converge to the time domain minimum mean square error (MMSE) if signal components are not aligned to frequency bins, resulting in a large worst case error. To mitigate this problem of the so-called independent frequency bin (IFB) processor, overlap-save based GSC beamforming structures have been explored. This system address the minimisation of the time domain MMSE, with a significant reduction in computational complexity when compared to time-domain implementations, and show a better convergence behaviour than the IFB beamformer. By studying the effects that the blocking matrix has on the adaptive process for the overlap-save beamformer, several modifications are carried out to enhance both the simplicity of the algorithm as well as its convergence speed. These modifications result in the GSC beamformer utilising a significantly lower computational complexity compare to the time domain approach while offering similar convergence characteristics. In certain applications, especially in the areas of acoustics, there is a need to maintain constant resolution across a wide operating spectrum that may extend across several octaves. To attain constant beamwidth is diffcult, particularly if uniformly spaced linear sensor array are employed for beamforming, since spatial resolution is reciprocally proportional to both the array aperture and the frequency. A scaled aperture arrangement is introduced for the subband based GSC beamformer to achieve near uniform resolution across a wide spectrum, whereby an octave-invariant design is achieved. This structure can also be operated in conjunction with adaptive beamforming algorithms. Frequency dependent tapering of the sensor signals is proposed in combination with the overlap-save GSC structure in order to achieve an overall frequency-invariant characteristic. An adaptive version is proposed for frequency-invariant overlap-save GSC beamformer. Broadband adaptive beamforming algorithms based on the family of least mean squares (LMS) algorithms are known to exhibit slow convergence if the input signal is correlated. To improve the convergence of the GSC when based on LMS-type algorithms, we propose the use of a broadband eigenvalue decomposition (BEVD) to decorrelate the input of the adaptive algorithm in the spatial dimension, for which an increase in convergence speed can be demonstrated over other decorrelating measures, such as the Karhunen-Loeve transform. In order to address the remaining temporal correlation after BEVD processing, this approach is combined with subband decomposition through the use of oversampled filter banks. The resulting spatially and temporally decorrelated GSC beamformer provides further enhanced convergence speed over spatial or temporal decorrelation methods on their own.
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Ghiaasi-Hafezi, Golsa. "Broadband Low Noise Frequency Synthesizers for Future Wireless Communication Systems." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1253600913.
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Karjalainen, J. (Juha). "Broadband single carrier multi-antenna communications with frequency domain turbo equalization." Doctoral thesis, Oulun yliopisto, 2011. http://urn.fi/urn:isbn:9789514295027.
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Abstract This thesis focuses on advanced multi-antenna receiver and transmission techniques to improve the utilization efficiencies of radio resources in broadband single carrier communications. Special focus is devoted to the development of computationally efficient frequency domain (FD) turbo equalization techniques for single and multiuser MIMO frequency selective channels. Another special emphasis is given to transmission power optimization for single user MIMO communications, which takes into account the convergence properties of the iterative equalizer. A new iterative FD soft cancellation (SC) and minimum mean square error (MMSE) filtering based joint-over-antenna (JA) multiuser MIMO signal detection technique for multiuser MIMO uplink transmission in frequency-selective channels is proposed. The proposed FD multiuser MIMO detection technique requires significantly lower computational complexity than its time-domain counterpart. Furthermore, significant performance gains can be achieved with the proposed JA turbo receiver compared to an antenna-by-antenna (AA) turbo receiver when the total number of transmitter antennas and users is larger than the number of receiver antennas, as well as in the presence of spatial correlation. The impact of existing linear precoding techniques, e.g, maximum information rate (MaxRate) and minimum sum mean square error (MinSumMSE), on the performance of frequency domain turbo equalization is investigated by utilizing extrinsic information transfer (EXIT) chart analysis. A novel transmission power minimization framework based on an EXIT analysis of single carrier MIMO transmission with iterative FD SC-MMSE equalization is then proposed. The proposed optimization framework explicitly takes into account the convergence properties of the iterative equalizer. The proposed convergence constrained power allocation (CCPA) technique decouples the spatial interference between streams using singular value decomposition (SVD), and minimizes the transmission power while achieving the mutual information target for each stream after iterations at the receiver side. The transmission power allocation can be formulated as a convex optimization problem. A special case having only two mutual information constraints is considered, for which the Lagrange dual function is derived and its dual problem is solved. Inspired by the Lagrange duality, two CCPA based heuristic schemes are developed. The numerical results demonstrate that the proposed CCPA schemes outperform the existing power allocation schemesTiivistelmä Tässä työssä tutkitaan edistyksellisten moniantennivastaanotto- ja lähetysmenetelmien käyttöä radioresurssien tehokkuuden parantamiseen laajakaistaisessa yhden kantoaallon kommunikaatiossa. Työssä keskitytään erityisesti laskennallisesti tehokkaiden taajuustasossa suoritettavien iteratiivisten kanavakorjaintekniikoiden kehittämiseen yhden ja usean käyttäjän multiple-input multiple-output (MIMO) -kommunikaatiossa taajuusselektiivisen radiokanavan yli. Toinen tutkimuksen painopiste on lähetystehon optimointi yhden käyttäjän MIMO-kommunikaatiossa, jossa iteratiivisen kanavakorjaimen konvergenssiominaisuudet otetaan huomioon. Työssä ehdotetaan uudenlaista iteratiivista taajuustasossa suoritettavaa soft-cancellation (SC) ja minimum mean square error (MMSE) -suodatukseen pohjautuvaa joint-over-antenna (JA) monen käyttäjän ilmaisumenetelmää nousevan siirtokanavan tiedonsiirtoon taajuusselektiivisessa radiokanavassa. Ehdotettu tajuustasossa suoritettava usean käyttäjän MIMO-lähetyksen ilmaisumenetelmä vaatii selvästi vähemmän laskentatehoa verrattuna aikatason menetelmään. Tämän lisäksi ehdotetulla menetelmällä voidaan saavuttaa merkittävää suorituskykyhyötyä verrattuna antenna-by-antenna (AA) -pohjaiseen iteratiiviseen vastaanottimeen kun lähetysantennien ja käyttäjien kokonaislukumäärä on suurempi kuin vastaanotinantennien. Suorituskykyhyöty pätee myös tilakorrelaation tapauksessa. Työssä tutkitaan lisäksi olemassa olevien lineaaristen esikoodaustekniikoiden, esim. maximum information rate (MaxRate) and minimum sum mean square error (MinSumMSE), vaikutusta taajuustasossa suoritettavaan iteratiivisen kanavakorjaimen konvergenssiominaisuuksiin xtrinsic information transfer (EXIT) -analyysin avulla. Työssä ehdotetaan uudenlaista EXIT-analyysi-pohjaista lähetystehon minimointimenetelmää yhden kantoaallon MIMO-lähetykseen käyttäen iteratiivista taajuustason SC-MMSE-kanavakorjainta. Menetelmä ottaa huomioon iteratiivisen kanavakorjaimen konvergenssiominaisuudet. Ehdotettu convergence constrained power allocation (CCPA) -menetelmä erottaa tilatason häiriön lähetteiden välillä hyödyntäen singular value decomposition (SVD) -tekniikkaa ja minimoi lähetystehon ja saavuttaa samalla keskinäisinformaatiotavoitteet jokaiselle lähetteelle iteraatioiden jälkeen vastaanottimessa. Lähetystehon minimointiongelma voidaan muotoilla konveksiksi optimointiongelmaksi. Kahden keskinäisinformaatiorajoitteen erityistapaukselle johdetaan Lagrangen duaalifunktio ja ratkaistaan sen duaalifunktio. Työssä kehitetään lisäksi kaksi CCPA-pohjaista heuristista menetelmää. Numeeriset tulokset osoittavat ehdotettujen CCPA-pohjaisten menetelmien suoriutuvan paremmin verrattuna olemassa oleviin menetelmiin
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Srivastava, Abhishek. "High Frequency Study of Magnetic Nanostructures." ScholarWorks@UNO, 2012. http://scholarworks.uno.edu/td/1530.
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The work in this thesis is divided in three parts. In part one we developed electrodeposition method of Nickel Nanowire in commercial AAO template in constant current (Galvanostatic) mode, further we tried to estimate the growth rate from theory, from saturation magnetization and direct measurement from SEM image.
In part two we focused on using the Vector Network Analyzer (VNA) to measure the Ferromagnetic Resonance (FMR))of various magnetic Nanowire arrays. We employed different measurement geometries using microstripline and coplanar waveguide as microwave transmission lines.
In part three our aim was to study the magnetic properties of complex ferromagnetic system, especially the effect of interactions on dynamic properties of magnetic nanostructures (nanowire arrays and exchange biased ferromagnetic-antiferromagnetic multilayers). Our effort was centered on using ferromagnetic resonance to understand the dynamic response of these systems.
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Fragoulis, Ioannis. "An investigation of two broadband HF shipboard communication antennas." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA245608.
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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, December 1990.Thesis Advisor(s): Adler, Richard W. Second Reader: Vincent, Wilbur R. "December 1990." Description based on title screen as viewed on March 30, 2010. DTIC Identifier(s): Ship Antennas, Communication Antennas, Antenna Radiation Patterns, High Frequency, Multiwire Antennas, Theses. Author(s) subject terms: Inverted Cone Antenna, Computer Antenna Modeling, NEC, HF Antennas, Shipboard Antenna. Includes bibliographical references (p. 95). Also available in print.
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Viegas, Colin. "Broadband Schottky diode components for millimeter-wave instrumentation." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/broadband-schottky-diode-components-for-millimeterwave-instrumentation(93ced9dc-f866-418f-a525-742008b89b88).html.
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Terahertz source technology has been an active area of research for a number of years. This has helped develop continuous wave solid-state sources that are highly desirable in a wide range of applications spanning from Earth science to medical science. However, even with advances in terahertz technology, the generation of fundamental source power at these frequencies is still challenging. Promising electronic solid-state devices fall short in overcoming source power shortage due to electronic breakdown mechanism and fabrication limits at terahertz frequencies. The fundamental physical limitation of photonic devices, such as low photon energy, force cryogenic operation which at times is impractical. Schottky diode frequency multipliers often offer a very practical solution for generating continuous wave radiation based on solid-state technology. This harmonic source technology is today a most certain candidate for many applications where compactness and room temperature operation is desired. However, despite of all the advances in Schottky diode fabrication and their use in frequency multiplication, output power falls rapidly with increasing frequency. Thermal constrains, fabrication limits, assembly errors and parasitic losses all constitute changes that affect the performance of these devices and make it difficult to reproduce experimental data. To overcome these problems and progress towards the generation of milliwatts of power at terahertz frequencies, the study of existing methods to generate and handle high power is necessary. In the first part of the thesis, the design, fabrication and development of two Schottky diode-based frequency doublers is discussed. The work focuses on the generation of high-power sources that are capable of handling higher input powers while maintaining good thermal efficiencies. A detailed study into the machining tolerances, assembly errors and temperature effects are evaluated for the frequency doublers. High frequency effect such as velocity saturation is also addressed. Depending on the design frequency and power handling, two different circuit configurations are employed for the frequency doublers. While the high-power 80/160 GHz frequency doubler used a discrete flip-chip diode configuration, the 160/320 GHz frequency doubler employed an integrated diode membrane to mitigate sensitivity issues encountered during assembly and enable correlation between simulated and measured data. The second part proposes the use of millimeter-wave Schottky diode-based radiometers for imaging of composites samples. The focus of this experiment is the introduction of an alternate EM inspection method with the use of broadband Schottky diode components. This technique combines two different fields {--} non-destructive testing and radiometry, which presents a potentially new and interesting area for research. Since no single method can qualify to be the most accurate for all inspections, and with the future integration bringing down manufacturing costs of high frequency components, this demonstration presents a new approach to consider for future material imaging and evaluation experiments.
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Alfonzo, Miguel. "Post‐processing of Airborne data using the Broadband Frequency Receiver instrument ADU07." Thesis, Uppsala universitet, Geofysik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-183710.
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In August 2008 and June 2009 two sets of airborne measurements were made in Falun and Borlänge, respectively, by the Geological Survey of Sweden (SGU). The purpose of these campaigns was to test the new Multi Frequency Receiver (MFR) instrument called ADU07 for the collection of airborne data in the VLF and LF bands. This system was designed by Metronix and adapted by Uppsala University together with the SGU in the frame of a joint research project. The SGU in its bedrock mapping program routinely records VLF signals from only two transmitters in the frequency band of 14‐30 kHz. The RMT technique also makes use of electromagnetic signals in both the VLF and LF bands in the frequency range of 10‐250 kHz. By measuring all the three magnetic field components in this broader band, the data acquired by the new MFR system can provide high lateral and vertical resolution compared to the VLF data. This can be done by applying the concepts used for the EnviroMT. The joint research therefore aims at extending the VLF technique currently used by the SGU for geophysical investigations and whereby generating improved and more detailed anomaly maps. The airborne measurements with the ADU07 system were performed by continuously recording the three magnetic field components with a sampling frequency of 512 kHz in three channels. The prior evaluation of the data gave good results in the beginning. However, later tests showed that there were some near field sources onboard the aeroplane that contaminated the data and highly affected the estimation of transfer functions from the radio transmitters’ signals. The noise was basically generated by other measuring instrumentation and the common power supply used to feed both the ADU07 and the PC controller. The main aim of the present project is to develop a processing method that identifies frequencies from these near field sources and filters them out from the spectral ADU07 data. This work has been carried out by writing MATLAB routines. After the filtering, more reliable transfer functions that provide relevant information about the Earth’s resistivity structure can be estimated. Different methods were applied in order to detect the noise in the data. The mean value of the real part of the vertical magnetic field component (Hz) and the scalar tippers were firstly calculated along the profiles. These values should normally be close to zero. These methods did not give any valuable information since no patterns could be seen in the results. Afterwards, the vertical signal‐to‐noise ratio (VSNR) was calculated for every frequency at each station. This criterion showed that, for the first campaign, there were practically two sets of noise frequencies in the spectra: the first group corresponds to the even and odd harmonics of frequency 8 kHz, and the second group to frequency 23.47 kHz and its harmonics. For the last campaign, frequency 10.28 kHz and its harmonics were identified. The band averaging technique that splits the main frequency band into 9 overlapping sub‐bands with 1 octave of width was used. Finally, Prediction Errors (PE’s) were estimated to detect the remaining noise. A threshold was then chosen in order to remove from the spectra those frequencies with a PE above 3 and up to 20% of the number of transmitters in the sub‐bands. These processing steps improved considerably the tipper behaviour for the VLF band along the profiles, although some noise was also added. For the LF band, the filtering steps seem to have worsened the data quality and therefore the tipper estimation. The removal of important frequencies that were hidden in the high noise levels and the useof some other instruments during the data collection could be the causes of these responses.
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Holroyd, Chloe. "Broadband vibrational sum frequency spectroscopy (VSFS) of modified graphene and polymeric thin films." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/broadband-vibrational-sum-frequency-spectroscopy-vsfs-of-modified-graphene-and-polymeric-thin-films(1b1abe44-8679-4384-993f-f9547f41f450).html.
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The surface-specific technique of vibrational sum frequency spectroscopy (VSFS) can provide vibrational information about chemical bonds at surfaces and interfaces. Two photons, of visible and infrared frequency, are spatially and temporally overlapped at a surface/interface to produce a photon at the sum frequency (SF) of the two input photons. As well as this process only being allowed in non-centrosymmetric media (i.e. VSFS is surface/interface specific), the SF process is enhanced when the IR beam is resonant with vibrational resonances. Broadband VSFS has been used in this project to study surfaces of two distinct classes of materials, namely graphene and polymers. Firstly, broadband VSFS was used to investigate the heating polymeric thin films using a home-built heated sample cell. The cell was tested using self-assembled monolayers (SAMs) of 1-octadecanethiol (ODT) grown on gold substrates. It was subsequently used to investigate thin films of poly(methyl methacrylate) (PMMA) of four different thicknesses and two different molecular weights that were spin-coated onto gold substrates. It was shown that the monolayers of ODT become disordered upon heating and solidified to incorporate the disorder introduced by the heating process. The PMMA films were also shown to become more disordered as a function of temperature. Secondly, broadband VSFS was used to investigate modified graphene, motivated by the fact that modifications to pristine graphene, be it intentional (i.e. functionalisation) or unintentional (i.e. contamination), cause the properties of graphene to change. This project focused on studying hydrogenated graphene, N-methylbenzamide functionalised graphene and contamination on commercial graphene. A method for calculating the number of hydrogen atoms in a hydrogen island was developed. VSF spectra of CH stretches in N-methylbenzamide functionalised graphene were obtained. Residues on commercially bought graphene were detected using VSFS and RAIRS. These residues were assigned to PMMA that remained on the CVD graphene by the process of transferring the CVD graphene from the copper foil on which it was grown onto the gold substrates.
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Oksar, Irfan. "Design And Realization Of Mixed Element Broadband Bandpass Filters." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/4/1092964/index.pdf.
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In this thesis, a highly selective broadband hybrid bandpass filter operating between 0.4-2.0 GHz with a stopband up to 7 GHz is designed and analyzed. The realization is carried out by hybrid method, which combines both lumped and distributed element filters. In this approach, two separate filters, which are lumped highpass with 0.4 GHz corner frequency and distributed stripline lowpass with 2 GHz corner frequency, are combined to get the bandpass filter that has a passband in between 0.4 to 2.0 GHz. The usage of the lumped elements for the highpass filter resulted in a great size reduction compared to distributed element approach. The design software FILPRO&tradeis used to synthesize the trial filters. More than forty filters are synthesized, and among them, the ones that have better properties are chosen for further processes. Optimization, modeling and electromagnetic simulations of the selected lumped and distributed filters are carried out on the software GENESYS&trade
. Distributed filters are also simulated using the software SONNET&trade
. After the simulations, all of the simulated filters are realized and measured, and the level of consistency with the simulations is observed. According to the results of the measurements, the filter combination that has the best combination of low insertion loss, small dimensions, high stopband attenuation and low spur levels is selected for the final bandpass filter structure and a few variants are examined to get the final structure.
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McCormick, Jackson C. "Spatial and temporal ionospheric monitoring using broadband sferic measurements." Thesis, Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54469.
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The objective of this thesis is to use radio emissions from lightning, known as `radio atmospherics' or `sferics', to study the temporal and spatial variation of the lower ionosphere, a layer of ionized atmosphere beginning at $\sim$70 km altitude (D-region). Very Low Frequency (VLF, 3$-$30kHz) radio waves are a useful diagnostic for lower ionospheric monitoring due to their reflection from this region and global propagation. Traditionally, the lower ionosphere has been sensed using single-frequency VLF transmitters allowing for analysis of a single propagation path, as there are only a small number of transmitters.
A lightning stroke, however, releases an intense amount of impulsive broadband VLF radio energy in the form of a sferic, which propagates through the Earth-ionosphere waveguide. Lightning is globally distributed and very frequent, so a sferic is therefore also a useful diagnostic of the D-region. This is true both for ambient or quiet conditions, and for ionospheric perturbations such as solar flare x-ray bursts. Lightning strokes effectively act as separate VLF transmitting sources. As such, they uniquely provide the ability to add a spatial component to ionospheric remote sensing, in addition to their broadband signature which cannot be achieved with man-made transmitters.
We describe the methods of processing in detail. As an example, we analyze a solar flare during which time there is a significant change in magnitude and frequency content of sferics. This disturbance varies with distance from the source, as well as time. We describe the methods of processing in detail, and show results at Palmer Station, Antarctica for both a quiet and active solar day.
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Rouse, Jerry Wayne. "Energy-Based Boundary Element Method for High-Frequency Broadband Sound Fields in Enclosures." NCSU, 2000. http://www.lib.ncsu.edu/theses/available/etd-20000911-161316.
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This work sets forth a new method for predicting the spatialvariation of mean square pressure within two-dimensionalenclosures containing high-frequency broadband sound fieldsand light to moderate absorption. In the new method, theenclosure boundaries are replaced by a continuousdistribution of broadband uncorrelated sources, each ofwhich provides a constituent field expressed in terms ofmean square pressure and time average intensity variables.Superposition of these fields leads to the overall meansquare pressure and time average intensity as a function ofposition. Boundary conditions for radiating and absorbingsurfaces are recast in terms of energy and intensityvariables. The approach is implemented as a boundaryelement formulation for efficient evaluation of the pressureand intensity fields in enclosures. In contrast totraditional boundary element methods, the new method isindependent of frequency. A two-dimensional model problemenclosure is investigated to verify the new method. The exact analytical solution for the mean square pressuredistribution within the model problem enclosure is obtainedand compared to the results predicted by the new method.The comparisons indicate that the new method is asignificant improvement upon classical diffuse field theoryand computationally efficient relative to traditional boundary element methods and ray tracing techniques.
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Qatawneh, Ibrahim Awad Zamil. "The use of orthogonal frequency division multiplex (OFDM) techniques in mobile broadband applications." Thesis, University of Huddersfield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363241.
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Verma, Arti. "Broadband Echosounder Calibration and Processing for Frequency Dependent Target Strength and Phase Measurements." Thesis, Curtin University, 2019. http://hdl.handle.net/20.500.11937/80865.
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An analysis technique is developed for the calibration and processing for the target strength and phase spectra using a broadband echosounder. A new variable ‘residual phase’ is introduced, which could be used as a target classifier. Implementation of the method to characterise marine organism from the open ocean, demonstrated consistent target strength and residual phase and the matching of both the variables to the output of the numerical scattering model verified the method.
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Chheda, Shital Ratilal. "A Comparison Between Synchronous CDMA and Orthogonal Frequency Division Multiplexing (OFDM) for Fixed Broadband Wireless Access." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/31896.
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The growth of broadband Internet access has paved the way for the development of many new technologies. As the cost of implementing broadband access soars, the best alternative will be to use fixed wireless for these services. This thesis addresses the possibility of 3rd Generation (3G) mobile cellular wireless systems as the basis for fixed broadband wireless service. Two of the 3G technologies aimed at providing fixed broadband wireless access are Time Division Synchronous Code Division Multiple Access (TD-SCDMA) and Orthogonal Frequency Division Multiplexing (OFDM).
This thesis aims to provide a preliminary study on using TD-SCDMA and OFDM for broadband wireless systems. Currently, there is not enough theory and information to establish the feasibility of using either of these technologies for broadband wireless access. First, the basic features and background on synchronous CDMA and OFDM are presented for the reader to better understand these technologies. Then, an example TD-SCDMA system is described, and some analytical and experimental results are presented. Finally, TD-SCDMAâ s technologies, along with this systemâ s attributes, are compared analytically to that of Vector OFDM (VOFDM).
Master of Science
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Huang, Wenxiang. "A broadband RF CMOS frond-end for multi-standard wireless communication." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1170882877.
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Banerjee, Bhaskar. "Development of Broadband Noise Models and Radio Frequency Integrated Circuits using Silicon Germanium HBTs." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/13984.
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A novel transit time based analytical broadband noise model is developed and implemented for high frequency bipolar transistors. This model is applied to a complementary (npn + pnp) silicon germanium (SiGe) heterojunction bipolar transistors (HBT). A complete set of analytical equations are derived using this transit time noise model, to express the four fundamental noise parameters in terms of device parameters.
A comprehensive analysis on the ac, dc and broadband noise performance of a 200 GHz SiGe HBT technology, under cryogenic temperatures, is presented. The transit time based noise model is used to analyze the RF noise behavior of the SiGe HBT down to 85 K. Significant performance gain is demonstrated in cryogenic temperatures indicating the suitability of SiGe HBT for extreme environment electronics.
A sub-circuit based substrate parasitic modeling methodology, in silicon based processes, is presented. A test case low noise amplifier, operating in the 5 GHz band, is designed in a SiGe HBT process and is used to demonstrate the validity of the design methodology. A dual-band, dual-mode transceiver front end for IEEE802.11a/b/g WLAN applications, is designed in a 0.8 and #956;m SiGe HBT process. The transceiver uses a new architecture which uses an on-chip frequency doubler and a single off-chip frequency synthesizer for both the 2.4 and 5 GHz bands. The performance of the transceiver meets the specification of the IEEE802.11a/b/g standards.
The work described in the dissertation significantly advances the state-of-the-art in bipolar broadband noise modeling and RF, microwave circuit design using silicon based processes. The contributions and implications of this work for future research are discussed.
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Chronopoulos, Dimitrios. "Prediction of the vibroacoustic response of aerospace composite structures in a broadband frequency range." Phd thesis, Ecole Centrale de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-00787864.
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During its mission, a launch vehicle is subject to broadband, severe, aeroacoustic and structure-borne excitations of various provenances, which can endanger the survivability of the payload and the vehicles electronic equipment, and consequently the success of the mission. Aerospace structures are generally characterized by the use of exotic composite materials of various configurations and thicknesses, as well as by their extensively complex geometries and connections between different subsystems. It is therefore of crucial importance for the modern aerospace industry, the development of analytical and numerical tools that can accurately predict the vibroacoustic response of large, composite structures of various geometries and subject to a combination of aeroacoustic excitations. Recently, a lot of research has been conducted on the modelling of wave propagation characteristics within composite structures. In this study, the Wave Finite Element Method (WFEM) is used in order to predict the wave dispersion characteristics within orthotropic composite structures of various geometries, namely flat panels, singly curved panels, doubly curved panels and cylindrical shells. These characteristics are initially used for predicting the modal density and the coupling loss factor of the structures connected to the acoustic medium. Subsequently the broad-band Transmission Loss (TL) of the modelled structures within a Statistical Energy Analysis (SEA) wave-context approach is calculated. Mainly due to the extensive geometric complexity of structures, the use of Finite Element(FE) modelling within the aerospace industry is frequently inevitable. The use of such models is limited mainly because of the large computation time demanded even for calculations in the low frequency range. During the last years, a lot of researchers focus on the model reduction of large FE models, in order to make their application feasible. In this study, the Second Order ARnoldi (SOAR) reduction approach is adopted, in order to minimize the computation time for a fully coupled composite structural-acoustic system, while at the same time retaining a satisfactory accuracy of the prediction in a broadband sense. The system is modelled under various aeroacoustic excitations, namely a diffused acoustic field and a Turbulent Boundary Layer (TBL) excitation. Experimental validation of the developed tools is conducted on a set of orthotropic sandwich composite structures. Initially, the wave propagation characteristics of a flat panel are measured and the experimental results are compared to the WFEM predictions. The later are used in order to formulate an Equivalent Single Layer (ESL) approach for the modelling of the spatial response of the panel within a dynamic stiffness matrix approach. The effect of the temperature of the structure as well as of the acoustic medium on the vibroacoustic response of the system is examined and analyzed. Subsequently, a model of the SYLDA structure, also made of an orthotropic sandwich material, is tested mainly in order to investigate the coupling nature between its various subsystems. The developed ESL modelling is used for an efficient calculation of the response of the structure in the lower frequency range, while for higher frequencies a hybrid WFEM/FEM formulation for modelling discontinuous structures is used.
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Gundry, Sarah. "Implementation of an ultra-broadband high power frequency modulator based on coherent molecular oscillation." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413552.
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Nigro, David. "Prediction of broadband aero and hydrodynamic noise : derivation of analytical models for low frequency." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/prediction-of-broadband-aero-and-hydrodynamic-noise-derivation-of-analytical-models-for-low-frequency(25bb8835-9cf8-488a-acc0-677a53122801).html.
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In this thesis we explore several topics with applications to both aero and hydroacoustics. Due to the much larger speed of sound in water compared to in air, several of the approximations used in aeroacoustics are not applicable underwater over the range of frequencies of interest. Specifically, we study the finite-chord effects on two broadband noise mechanisms: the trailing edge noise and the ingested noise problems. We start by investigating the acoustic wave diffraction by a finite rigid plate using three different methods. We compare the behaviour of the different solutions as a function of the reduced acoustic wavenumber. Our results reveal that the Mathieu function expansion is the most appropriate method as long as the reduced acoustic wavenumber is not too large. Finally, we show how the Mathieu functions can be used to build a Green's function tailored to an elliptic cylinder of arbitrary aspect ratio without relying on addition theorems. The results obtained in chapter two motivated the search for an exact solution to the trailing edge noise problem using a Mathieu function expansion. It is shown that the approximate methods used in aeroacoustics are not accurate enough for reduced acoustic wavenumbers less than unity, and for all wavenumbers near cut-off. Furthermore it is shown that, even at low Mach numbers, it is crucial to take into account the effects of convection at low frequency. Finally Lighthill's analogy is used, combined with the tailored Green's function introduced previously, to recover the two asymptotic Mach number scalings of the acoustic power for a flat plate at high frequency and low frequency. In chapter four, we introduce a novel method to solve the ingested noise problem by decomposing the pressure field into a singular part whose functional form can easily be found, and a regular part that we express using a Mathieu function expansion. It was found that finite-chord effects do have a strong impact for reduced acoustic wavenumbers less than unity, and for all wavenumbers near cut-off. The following chapter focuses on the trailing edge noise mechanism and details how the theory for a single stationary aerofoil can be applied to a rotating propeller. Due to the general geometry of a blade, we extended Amiet's model to take into account a mean flow misaligned with the blade chordline. Different semi-analytical models of wall pressure spectra are introduced and compared. We make extensive use of Brooks' data for a NACA 0012 aerofoil to obtain realistic inputs in the semi-analytical models. Finally, we introduce and compare two models of rotating blade trailing edge noise. The effects of both the angle of attack and the number of strips are then investigated. The final chapter is distinct from the rest of the thesis. We propose a model for studying the low Mach number flow noise from a 2D circular cylinder with small roughness. The method is based on using the Green's function tailored to a smooth cylinder in Curle's acoustic analogy. It was found that the main source of noise was the tonal low frequency scattering by the smooth geometry. However, it is suggested that roughness elements might be the dominant source of noise at higher frequency.
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Jayalath, A. D. S. (Angiyaddage Dhammika Srilal) 1967. "OFDM for wireless broadband communications (peak power reduction, spectrum and coding)." Monash University, School of Computer Science and Software Engineering, 2002. http://arrow.monash.edu.au/hdl/1959.1/7995.
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Jayalath, A. D. S(Angiyaddage Dhammika Srilal) 1967. "OFDM for wireless broadband communications(peak power reduction, spectrum and coding) /." Monash University, School of Computer Science and Software Engineering, 2002. http://arrow.monash.edu.au/hdl/1959.1/7995.
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Enchelmaier, David Samuel. "A miniaturised wideband frequency synthesiser." Thesis, Queensland University of Technology, 2009. https://eprints.qut.edu.au/31851/1/David_Enchelmaier_Thesis.pdf.
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Wideband frequency synthesisers have application in many areas, including test instrumentation and defence electronics. Miniaturisation of these devices provides many advantages to system designers, particularly in applications where extra space and weight are expensive.
The purpose of this project was to miniaturise a wideband frequency synthesiser and package it for operation in several different environmental conditions while satisfying demanding technical specifications. The four primary and secondary goals to be achieved were:
1. an operating frequency range from low MHz to greater than 40 GHz, with resolution better than 1 MHz,
2. typical RF output power of +10 dBm, with maximum DC supply of 15 W,
3. synthesiser package of only 150 100 30 mm, and
4. operating temperatures from 20C to +71C, and vibration levels over 7 grms.
This task was approached from multiple angles. Electrically, the system is designed to have as few functional blocks as possible. Off the shelf components are used for active functions instead of customised circuits. Mechanically, the synthesiser package is designed for efficient use of the available space. Two identical prototype synthesisers were manufactured to evaluate the design methodology and to show the repeatability of the design.
Although further engineering development will improve the synthesiser’s performance, this project has successfully demonstrated a level of miniaturisation which sets a new benchmark for wideband synthesiser design. These synthesisers will meet the demands for smaller, lighter wideband sources. Potential applications include portable test equipment, radar and electronic surveillance systems on unmanned aerial vehicles. They are also useful for reducing the overall weight and power consumption of other systems, even if small dimensions are not essential.
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Krishnamurthy, Prashant Venkatanarayana. "A combined frequency, code and time division multiple-access technique for broadband indoor wireless communications." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=24062.
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Commutation signalling is an antimultipath technique employing direct-sequence bandwidth spreading for combatting multipath induced ISI. We propose a CDMA-like multiple-access scheme which utilizes this inherent spreading for broadband cellular indoor wireless communications. The intra-cell multiple-access is by time division while the inter-cell interference is reduced via combined frequency and code division. The frequency bands of adjacent cells overlap to increase bandwidth efficiency. We consider the interference between spread-spectrum signals with partially overlapping spectra and apply the results to the analysis of this cellular system. The uplink and downlink are considered with and without cell sectorization. The downlink is used for obtaining certain system design parameters and for comparing the merits of different pulse shapes. We finally compare the proposed scheme with the usual TDMA/FDMA and CDMA schemes. The proposed scheme is found to require less bandwidth compared to the usual TDMA/FDMA scheme. However, CDMA requires a lesser bandwidth than the proposed scheme since it employs powerful very low rate channel coding techniques.
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Behrle, Charles D. "Computer simulation studies of multiple broadband target localization via frequency domain beamforming for planar arrays." Thesis, Monterey, California. Naval Postgraduate School, 1988. http://hdl.handle.net/10945/22976.
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Approved for public release; distribution is unlimitedComputer simulation studies of a frequency domain adaptive beamforming algorithm are presented. These simulation studies were conducted to determine the multiple broadband target localization capability and the full angular coverage capability of the algorithm. The algorithm was evaluated at several signal-to-noise ratios with varying sampling rates. The number of iterations that the adaptive algorithm took to reach a minimum estimation error was determined. Results of the simulation studies indicate that the algorithm can localize multiple broadband targets and has full angular coverage capability.
http://archive.org/details/computersimulati00behr
Lieutenant, United States Navy
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Thamrin, Cindy. "Measurement of lung function using broadband forced oscillations /." Connect to this title, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0103.
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Zand, Emad Dolatshahi. "Measurement of TOA using frequency domain techniques for indoor geolocation." Link to electronic thesis, 2003. http://www.wpi.edu/Pubs/ETD/Available/etd-0428103-130325.
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Huang, Defeng. "Low complexity diversity combining and carrier frequency offset compensation for ubiquitous OFDM based broadband wireless communications /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202004%20HUANG.
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Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2004.Includes bibliographical references (leaves 163-171). Also available in electronic version. Access restricted to campus users.
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Bolas, Eduardo José Ludovico. "Broadband VHF maritime communications based on cognitive radio." Doctoral thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/16285.
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Doutoramento em Engenharia EletrotécnicaTraditionally, maritime business is associated to transportation, which represents about 90% of global trade, and fishery, but new activities at sea, opened up by technological innovations, are transforming economical context of maritime services and resources. In the future, the massive use of technology to support endurance and ranging of maritime operations, namely in intelligent transport systems and autonomous vehicles areas, would lead to federations of maritime based embedded computing devices. Nevertheless, existing systems are not prepared to support such paradigm change. Currently, stovepiped systems rely on narrowband communications systems, where voice and low data rate are the most common used services, and specific broadband applications, such as Internet access, are supported by satellite communications (SATCOM). Unfortunately, UMTS/LTE networks do not provide consistent solutions, due their limited sea coverage, so there is a need for an additional capacity that can provide acceptable performances at low cost, which might act as a complement or even an alternative to satellite. We propose a Cognitive Radio based Broadband VHF (CR-B-VHF) communications solution to provide appropriate connectivity to support current information exchange requirements and enable future developments on maritime services and applications, thus avoiding SATCOM inconveniences. This CR-BVHF network would operate in a context of spectrum scarcity, within hierarchical spectrum access model, and use cognitive radio based concepts to implement a dynamic system that can activate and deactivated subcarriers, according to spectrum opportunities, ensuring an adequate interference level at incumbent's live services. The main contribution of this thesis work is the proposed CR-B-VHF framework and the demonstration of its suitability, feasibility and deployability. The presented relevancy analysis provides an overview of the state of the art on maritime business and its associated support communications and information systems, and prospects future requirements and applications for low-cost broadband access. The developed solutions for detection and exploitation of multiple non-contiguous narrowband spectrum opportunities in maritime VHF band, within a hierarchical spectrum access context, and their envisage performances, provide good indications regarding attainability of opportunistic BVHF systems and their future deployment. Finally, the discussion on regulatory and standardization issues intend to contribute for a shared problem solving, providing an end user perspective of hierarchical spectrum access. Despite the fact that technical aspects are nor the main issues on opportunistic systems deployment, novel proposed Spectrum Coherences Detector and its experimental demonstrated performances might be an important enabler and an additional argument to convince maritime communications stakeholders.
Tradicionalmente, a economia do mar está associada ao transporte marítimo, que representa cerca de 90% do comércio mundial, e à pesca, mas as novas atividades associadas à inovação tecnológica estão a transformar o contexto económico dos serviços e aplicações marítimas. No futuro, a utilização massiva de tecnologia no suporte às atividades desenvolvidas no mar, nomeadamente em transportes marítimos inteligentes e sistemas autónomos, conduzirá a uma federação de sistemas marítimos integrados. Contudo, as comunicações marítimas existentes não estão preparadas para dar suporte a esta alteração de paradigma. Atualmente, os sistemas dedicados baseiam-se em comunicações de banda estreita, onde a telefonia e a transmissão de dados de baixo débito são os serviços mais comuns, e aplicações de banda larga específicas, como o acesso a Internet, são disponibilizados através de comunicações por satélite (SATCOM). Infelizmente, as redes UMTS/LTE não providenciam soluções consistentes, devido à fraca cobertura sobre o mar. Por conseguinte, existe uma clara necessidade de capacidade adicional que possa disponibilizar desempenhos adequados a baixo custo e que possa constituir um complemento, ou mesmo uma alternativa, ao satélite. Nesta tese é proposta uma solução de comunicações de banda larga em VHF, baseada em rádio cognitivo (CR-B-VHF), que permite disponibilizar uma adequada conectividade de suporte aos requisitos atuais de troca de informação e a futuros desenvolvimentos nos serviços e aplicações marítimas, evitando as desvantagens da utilização do satélite. Esta rede foi concebida para operar num contexto de escassez de espectro, assumindo um modelo de acesso hierárquico, e utiliza conceitos de rádio cognitivo para implementar um sistema dinâmico que possa ativar e desativar sub-portadoras, de acordo com as oportunidades para transmitir, garantindo um adequado nível de interferência com os serviços dos incumbentes. O principal contributo deste trabalho é a proposta de um conceito de CR-B-VHF e a demonstração da sua adequabilidade, exequibilidade e aceitabilidade. A análise de relevância apresentada, proporciona uma perspetiva do estado da arte das atividades marítimas associadas à economia do mar e dos sistemas de informação e comunicação que lhes dão suporte, bem como uma perspetiva dos requisitos futuros e as aplicações para acessos de banda larga a baixo custo. As soluções desenvolvidas para a deteção e exploração de múltiplas e nãocontíguas oportunidades de banda estreita na banda marítima de VHF, e as suas previsíveis prestações, abrem boas perspetivas relativamente ao potencial dos sistemas oportunísticos na banda de VHF e a sua futura implementação. Finalmente, é apresentada uma discussão sobre questões regulatórias e de normalização, cujo objetivo é contribuir para a solução do problema da utilização partilhada do espectro, providenciando uma perspetiva de utilizador final, num modelo de acesso hierárquico ao espectro.
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Okonkwo, Igweani Uchenna Titus. "Optical fiber transmission systems for in-door next generation broadband access network." Thesis, Brunel University, 2014. http://bura.brunel.ac.uk/handle/2438/10539.
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This thesis investigates the generation and radio-over-fibre (RoF) transport of unlicensed 60 GHz millimetre-wave (mm-wave) frequency band. The investigated benefits of transmission schemes applicable for the mm-wave generation include optical carrier suppression (OCS), optical frequency multiplication (OFM) and remote heterodyne detection (RHD). For the in-door cabling of the mm-wave transmission, a low-cost polymer optical fibre (POF) along with bend-insensitive single mode fibre (BI-SMF) has been investigated for short-range networks. Transporting mm-wave generated signals over POF and BI-SMF cables based on OCS scheme showed results with the highest spectral efficiency and least inter-symbol interference over a 2.5 Gbit/s data delivery. Based on this thesis analysis, OCS simulation of POF showed the most reliable power penalty performance and receiver sensitivity at 30-m whilst the BI-SMF fiber produced equal observations at 150-m and more. In observing the free space links of delivering the RoF signal, the attenuation on the received signal power for both POF and BI-SMF was insignificant but expected, as the simulation assumed complete and total collimation of the light beams onto the aperture of the photodetector. OCS scheme for mm-wave generation and transport was explored based on the cost effectiveness of using one external modulator compared to other generation schemes that utilised more than one external modulator. OFM scheme was simulated to transport LTE and Wi-Fi signals along with 60 GHz RF band through both SMF and MMF-POF/BI-SMF cables. OFM transport scheme produced the highest attenuation on LTE, Wi-Fi and mm-wave signals carrying 100 Mbit/s data as simulated POF lengths increased. The best performance POF length was observed at 10-m. The application of offset launch technique at the coupling of SMF and POF showed insignificant improvement on signal bandwidth. The free space OFM transmission also demonstrated negligible change to the received signal power. This reinforces the attributes of deploying OWC system in an in-door environment. In other investigation, the simulated successful delivery of mm-wave signal using RHD scheme modulated and transported 10 Gbit/s data signal over POF and BI-SMF cables. Additional observed unrecorded result also showed BI-SMF cable maintained a 2% reduction of received power for 450-m fiber cable from 150-m. The attributes to RHD includes its low operating power system application and delivery of localised 60 GHz signal for uplink RoF transmission. The conceptualised design of Gigabit data delivery for indoor customer applications either through POF or BI-SMF cable, transporting various wireless channels has been presented in this thesis for the design of a robust next generation Broadband access network to reinforce the fiber-inside-the-home (FiTH) deployment.
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Sprague, John W. "Free space optics and wireless broadband radio frequency technology : bringing highspeed network access to the last mile." Thesis, Monterey, California. Naval Postgraduate School, 2002. http://hdl.handle.net/10945/6013.
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Approved for public release; distribution is unlimitedExisting copper phone and cable infrastructure no longer provide the required broadband for today's emerging applications. Homes and businesses in the "last mile" require the same access to broadband speeds available inside the fiber optic ring. It is not economically feasible, however, to bring fiber optic cable to each and every home and business in the "last mile." Free Space Optics and Wireless Broadband Radio Frequency are two technologies gaining popularity as an alternative broadband infrastructure. Free Space Optics uses lasers and Wireless Broadband uses Radio Frequency waves to send large amounts of data from one place to another. Both are wireless technologies that use free space. As a result, they are quickly deployed, easily scaled, and cheaper to install and upgrade than wired infrastructures. These characteristics support missions of the Armed Forces in which wire-bound infrastructure is not dependable, is impractical to build and maintain, or requires a high degree of mobility. This thesis addresses the "last mile" problem including why current infrastructure will not provide a broadband solution. Free Space Optics and Wireless Broadband Radio Frequency technologies are explored and discussed. Finally, an economic analysis of alternative network designs utilizing the two emerging technologies is applied to a fictitious city with a population of one million.
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Wolfe, Patrick Jason. "Perceptually motivated approaches to audio signal enhancement : broadband noise reduction via Bayesian modelling of time-frequency coefficients." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619708.
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Haas, Ellen Carla. "The perceived urgency and detection time of multi-tone and frequency-modulated warning signals in broadband noise." Diss., This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-10022007-145242/.
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Li, Guoqing. "Resource allocation in OFDMA networks /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/6136.
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Gill, Deshinder Singh. "Issues for the design and implementation of a novel frequency agile modem on a broadband local area network." Thesis, University of Sussex, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328348.
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Belleval, Christophe. "Robust Statistics Applied to Radio Astronomy : Radio Frequency Interference Mitigation and Automated Spectral Line Detection for Broadband Surveys." Thesis, Paris Sciences et Lettres (ComUE), 2019. http://www.theses.fr/2019PSLEO009.
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La nouvelle génération de radiotélescopes couplée avec les outils de numérisation à haute performance offrent des opportunités sans précédent en matière d'étude de l'environnement galactique et extragalactique. L'énorme quantité de données produites pose un certain nombre de défis, parmi lesquels : enregistrer des flux de données à très haut débit, en stocker temporairement des quantités considérables, adapter les logiciels à un traitement de masse, et fournir aux chercheurs des outils pratiques d'analyse.J'ai écrit cette thèse autour de deux thèmes. Premièrement la gestion des interférences électromagnétiques, et deuxièmement la mise au point de méthodes de détection automatique en aveugle de raies spectrales. Les algorithmes que je décris ont été développé à partir d'observations effectuées au radiotélescope décimétrique de Nanc{c}ay et enregistrées avec le spectromètre à large bande et haute fréquence d'échantillonnage WIBAR. Contrairement à l'analyse spectrale classique, ces algorithmes traitent les séries temporelles de densité de flux. Dans le but d'éliminer les interférences électromagnétiques et de détecter automatiquement des raies spectrales, j'ai choisi d'appliquer à ces séries temporelles des procédés issus des statistiques robustes, à savoir des paramètres de position, d'échelle, et de régression non linéaire qui sont insensibles aux données aberrantes.Dans la première partie, je présente les bases de la statistique appliquée à la radioastronomie, et plus spécifiquement des statistiques robustes appliquées à ce projet. Je décris les propriétés de différents paramètres de position, d'échelle et de régression, et en discute les avantages et inconvénients. Dans la seconde partie, après avoir présenté les caractéristiques du spectromètre WIBAR, j'expose les paradigmes et choix fondamentaux qui m'ont guidé dans le développement à cet effet du logiciel RObust Elusive Line detection (ROBEL). Dans la troisième partie, je présente et discute les résultats d'une part d'observations de radiosources effectuées avec WIBAR et traitées par ROBEL, d'autre part de la détection et de l'élimination de différents types d'interférences électromagnétiques. Je conclus en présentant les perspectives de développement, en particulier l'adaptation de tels procédés aux interféromètres dans le cadre de SKAThe advent of a new generation of radio telescopes coupled with digital processing hardware have provided tremendous new opportunities for extensive studies of the Galactic and extra galactic environment. In parallel, the nowadays huge amount of data produced has generated specific challenges. Among others: to secure high-speed data capture, to temporarily store huge quantities of raw data, to upgrade processing to this new data profile, and to provide researchers practical tools of analysis.In this thesis I have focused on two issues. Firstly the mitigation of radio frequency interference (RFI), and secondly practical methods for automated blind detection of spectral lines. The algorithms I present have been developed using observational data from the decimetric 100m-class single-dish Nanc{c}ay Radio Telescope (France) acquired with the WIBAR broadband and high sampling rate spectrometer. Contrary to classical spectral data analysis, The algorithms I have developed take into account time-series of flux-density. In order to excise RFI and detect spectral lines, I chose to apply robust statistics to these time-series, i.e., estimators of location and scale as well as regression which are immune to statistical outliers.In the first part, I lay down the basics of robust statistics applied to radio astronomy, used for this project: after having recalled basics of classical statistics in the context of radio astronomy, I discuss the pros and cons of several robust estimators of location and scale, followed by an evaluation of options for robust regression pertaining to the aims of this project. In the second part, I first describe the technical properties of the WIBAR broadband receiver, and then the fundamental assumptions and choices I have made to setup the architecture of the RObust Elusive Line detection (ROBEL) post-processing software I have developed for this matter. In the third part, I present results first from observations of different sources with WIBAR, and second related to RFI mitigation. After having discussed current issues, I conclude with possible future developments in interferometry in the SKA context