Dissertations / Theses on the topic 'Beamformer'
To see the other types of publications on this topic, follow the link: Beamformer.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Beamformer.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Tisdale, Neil. "Improved broadband adaptive beamformer performance." Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/158117/.
Full textAbstract:
The protection of wireless communications links against interference is a key concern in mission critical systems. In particular low probability of interception (LPI) systems which operate below the thermal noise floor of the receiver are particularly vulnerable. To protect against interference it is often necessary to include some form of active interference suppression. Broadband adaptive beamforming is one such technique which may be used to suppress interference by spatial and spectral filtering of the signals received by an array antenna. The hardware requirements of adaptive Beamforming systems are high in comparison to other approaches. As a result, the total number of adaptable weights realisable in the beamformer may be limited by the size, weight and power constraints of the system. This will limit the degrees of freedom in the beamformer and hence, the interference cancellation capability of the beamformer. The effectiveness of increasing the number of time-taps in space-time adaptive processors (STAP) as a method of increasing the number of interferers the beamformer can simultaneously cancel in an environment containing a mix of narrowband, partialband and broadband interference is studied. An alternative scheme to free up degrees of freedom in the beamformer is proposed based on frequency-domain excision to pre-filter narrowband interference before it reaches the beamformer. This approach frees up degrees of freedom in the beamformer, which would otherwise be consumed by the narrowband interference, for use in cancelling partialband and broadband interference. To enable the excision filters to identify narrowband interference while allowing partialband and broadband interference to pass through, a novel scheme is presented which produces a frequency mask that varies on a per-bin basis. Eigenanalysis of the beamformer's covariance matrix is used to explore the ability of frequency-domain excision to desensitise the beamformer to narrowband interference while bit error rate (BER) simulations demonstrate the enhanced interference protection the scheme affords an LPI communications link. Mismatches between the gain and phase responses of the radio-frequency (RF) front-end channels in broadband adaptive beamformers can limit their cancellation performance against higher power partialband and broadband interference. This performance limitation arises from the decorrelation experienced by the received signals across the array due to the interchannel mismatches. In STAP systems this performance limitation may be mitigated by increasing the number of taps per channel in the STAP. However, the computational complexity of adding additional time-taps tends to be high in STAP beamformers. Two new methods of interchannel mismatch compensation are proposed based on efficient frequency-domain methods. Simulations using software models and experiments using a hardware STAP system demonstrate the proposed techniques' ability to improve the cancellation performance where interchannel mismatches are limiting cancellation performance.
2
Howe, G. S. "A real-time adaptive beamformer for underwater telemetry." Thesis, University of Newcastle Upon Tyne, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307825.
Full text
3
Chau, Loo Kung Gustavo Ramón. "Robust Minimmun Variance Beamformer using Phase Aberration Correction Methods." Master's thesis, Pontificia Universidad Católica del Perú, 2017. http://tesis.pucp.edu.pe/repositorio/handle/123456789/8498.
Full textAbstract:
The minimum variance (MV) beamformer is an adaptive beamforming method that has the potential
to enhance the resolution and contrast of ultrasound images. Although the sensitivity of the MV
beamformer to steering vector errors and array calibration errors is well-documented in other fields, in
ultrasound it has been tested only under gross sound speed errors. Several robust MV beamformers
have been proposed, but have mainly reported robustness only in the presence of sound speed mismatches.
Additionally the impact of PAC methods in mitigating the effects of phase aberration in MV
beamformed images has not been observed
Accordingly, this thesis report consists on two parts. On the first part, a more complete analysis
of the effects of different types of aberrators on conventional MV beamforming and on a robust MV
beamformer from the literature (Eigenspace-based Minimum Variance (ESMV) beamformer) is carried
out, and the effects of three PAC algorithms and their impact on the performance of the MV beamformer
are analyzed (MV-PC). The comparison is carried out on Field II simulations and phantom experiments
with electronic aberration and tissue aberrators. We conclude that the sensitivity to speed of sound
errors and aberration limit the use of the MV beamformer in clinical applications, and that the effect
of aberration is stronger than previously reported in the literature. Additionally it is shown that under
moderate and strong aberrating conditions, MV-PC is a preferable option to ESMV.
On the second part, we propose a new, locally-adaptive, phase aberration correction method (LAPAC)
able to improve both DAS and MV beamformers that integrates aberration correction for each point in
the image domain into the formulation of the MV beamformer. The new method is tested using fullwave
simulations of models of human abdominal wall, experiments with tissue aberrators, and in vivo
carotid images. The LAPAC method is compared with conventional phase aberration correction with
delay-and-sum beamforming (DAS-PC) and MV-PC. The proposed method showed between 1-4 dB
higher contrast than DAS-PC and MV-PC in all cases, and LAPAC-MV showed better performance
than LAPAC-DAS. We conclude that LAPAC may be a viable option to enhance ultrasound image
quality of both DAS and MV in the presence of clinically-relevant aberrating conditions.Tesis
4
Koutrouli, Eleni. "Low Complexity Beamformer structures for application in Hearing Aids." Thesis, Blekinge Tekniska Högskola, Institutionen för tillämpad signalbehandling, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-17612.
Full textAbstract:
Background noise is particularly damaging to speech intelligibility for people with hearing loss. The problem of reducing noise in hearing aids is one of great importance and great difficulty. Over the years, many solutions and different algorithms have been implemented in order to provide the optimal solution to the problem. Beamforming has been used for a long time and has therefore been extensively researched. Studying the performance of Minimum Variance Distortionless Response (MVDR) beamforming with a three- and four- microphone array compared to the conventional two-microphone array, the aim is to implement a speech signal enhancement and a noise reduction algorithm. By using multiple microphones, it is possible to achieve spatial selectivity, which is the ability to select certain signals based on the angle of incidence, and improve the performance of noise reduction beamformers. This thesis proposes the use of beamforming, an existing technique in order to create a new way to reduce noise transmitted by hearing aids. In order to reduce the complexity of that system, we use hybrid cascades, which are simpler beamformers of two inputs each and connected in series. The configurations that we consider are a three-microphone linear array (monaural beamformer), a three-microphone configuration with a two-microphone linear array and the 3rd microphone in the ear (monaural beamformer), a three-microphone configuration with a two-microphone linear array and the 3rd microphone on contra-lateral ear (binaural beamformer), and finally four-microphone configurations. We also investigate the performance improvement of the beamformer with more than two microphones for the different configurations, against the two-microphone beamformer reference. This can be measured by using objective measurements, such as the amount of noise suppression, target energy loss, output SNR, speech intelligibility index and speech quality evaluation. These objective measurements are good indicators of subjective performance. In this project, we prove that most hybrid structures can perform satisfyingly well compared to the full complexity beamformer. The low complexity beamformer is designed with a fixed target location (azimuth), where its weights are calibrated with respect to a target signal located in front of the listener and for a diffuse noise field. Both second- and third- order beamformers are tested in different acoustic scenarios, such as a car environment, a meeting room, a party occasion and a restaurant place. In those scenarios, the target signal is not arriving at the hearing aid directly from the front side of the listener and the noise field is not always diffuse. We thoroughly investigate what are the performance limitations in that case and how well the different cascades can perform. It is proven that there are some very critical factors, which can affect the performance of the fixed beamformer, concerning all the hybrid structures that were examined. Finally, we show that lower complexity cascades for both second- and third- order beamformers can perform similarly well as the full complexity beamformers when tested for a set of multiple Head Related Transfer Functions (HRTFs) that correspond to a real head shape.
5
Sanyal, Alarka. "CMOS Phase Shifter for Conformal Phased Array Beamformer Applications." Thesis, North Dakota State University, 2015. https://hdl.handle.net/10365/27697.
Full textAbstract:
A vector modulator based phase shifter is developed using 0.18um CMOS process at S-band frequency to be integrated into a conformal phased array antenna to recover the desired radiation pattern in the entire 360? range. The phase shifter has a variable gain amplifier integrated into the circuit in order to vary gain along with phase for precise control to correct the degraded radiation pattern due to the conformal shaping. The results show state-of-the-art performances including more than 7dB conversion gain with variable feature, a continuous phase rotation of 360? with steps as low as 11.25? and very low power consumption of 17mW, for the first time to the best of the authors? knowledge. The chip size including all pads is 1.5mm X 0.75mm.ND NASA EPSCoR (Agreement FAR0020852)
6
Kale, Kaustubh R. "Low complexity, narrow baseline beamformer for hand-held devices." [Gainesville, Fla.] : University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0001223.
Full text
7
Malladi, Subrahmanya Sastry Venkata. "Modeling and Algorithm Performance For Seismic Surface Wave Velocity Estimation." University of Akron / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=akron1194630399.
Full text
8
Kompis, Martin. "Der adaptive Beamformer : Evaluation eines Verfahrens zur Störgeräuschunterdrückung für Hörgeräte /." Zürich, 1993. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=9960.
Full text
9
Paul, James G. "Simulation and analysis of a digital focused beamformer for SONAR." Thesis, Heriot-Watt University, 1992. http://hdl.handle.net/10399/812.
Full text
10
Juswardy, Budi. "Integrated broadband microphotonic beamformer for adaptive nulling in smart antennas." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2010. https://ro.ecu.edu.au/theses/1843.
Full textAbstract:
The tremendous growth of the wireless communications sector and the problem of limited available spectrum that can be used to cater the wireless demand have spurred the need for better data transmission capacity and signal rates for wireless communication systems. Smart antennas are the promising technology for improving the wireless communication systems performance. Smart antennas are system that consist of antenna arrays capable of adaptively adjusting the beam pattern, thereby enhancing the desired signals (beam steering) and suppressing the interference signals (null steering), which is also known as Space Division Multiple Access (SDMA). SDMA systems allow significant improvement in the area of capacity, signal bandwidth, signal-to-interference ratio, and frequency reuse. Due to the increasing complexity of the smart antennas system, innovations and improvements in miniaturisation, power consumption, and cost are needed. These breakthroughs could be achieved by combining the microelectronic and photonic technologies, leading to an innovative software-driven broadband MicroPhotonic beamforming system.
This thesis presents a doctoral study of integrated MicroPhotonic smart antenna beamformers. The beamformers presented in this study is based on microminiaturisation of hotonic and electronic components, which processes RF-modulated optical signals and adaptively synthesises multiple broadband null for interference suppression. Two types of beamformer are investigated in this thesis; the first form is based on delaying the input RF signal via discrete, high-resolution true-time delay (TTD) through the use of free space optics. The second type is based on continuous TTD generation using an Opto-VLSI processor in conjunction with high-dispersive optical fibres.
Design, simulation and proof-of-concept demonstration of some of the photonic building blocks and RF components of smart antennas that employ the MicroPhotonic beamformer are presented. These smart antennas are designed for use in adaptive broadband phased-array antenna applications including multimedia wireless transmission and RADAR.
11
Wu, Tsai-Fu. "A computationally efficient adaptive beamformer for noise fields with unknown covariance." Ohio : Ohio University, 1988. http://www.ohiolink.edu/etd/view.cgi?ohiou1182875752.
Full text
12
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.
Full textAbstract:
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.
13
Guo, Xinxin. "Back-propagation beamformer design with transverse oscillations for motion estimation in echocardiography." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0085/document.
Full textAbstract:
L'échographie est aujourd'hui l'une des modalités les plus populaires de diagnostic médical. Il permet d'observer, en temps réel, le mouvement des organes qui facilite le diagnostic des pathologies pour des médecins. L'échocardiographie [1, 2], l'imagerie du flux sanguin [3, 4] et l’élastographie [5-7] sont les domaines préférés de l'estimation de mouvement en utilisant l'échographie (en raison de son haut frame-rate).En conséquence, les images avec meilleurs qualités sont nécessaires. . En imagerie cardiaque, le système classique d'imagerie est limité dans la direction transversale (la direction perpendiculaire à celle de propagation). Travaillant sur la formation des images, ce problème peut être résolu en modifiant la façon de formateur de voie afin d'introduire des oscillations transversales (OTs) dans la fonction d’étalement du point (PSF). La technique d’oscillation transversale a montré son potentiel d'améliorer la précision de l'estimation de mouvement local dans la direction transversale (la direction perpendiculaire à celle de propagation). La classique OT en géométrie linéaire, basée sur l'approximation de Fraunhofer, relie la PSF et la fonction de pondération par la transformée de Fourier. Motivé par l'adaptation des OTs en échocardiographie, nous proposons une technique spécifique basée sur la rétro-propagation afin de construire des OTs en géométrie sectorielle. La performance de la méthode de rétro-propagation proposée a été étudiée progressivement, comparée avec la méthode de la transformée de Fourier, par exemple, l'évaluation de la qualité de la PSF quantifié, dans l'estimation de mouvement cardiaque en simulation, et en étude la qualité des PSF visuellement expérimentale. Les résultats quantifiés montrent les OT-images sont mieux contrôlés par la méthode proposée que par le formateur de voie conventionnelle. Une autre méthode, basée sur la décomposition d'onde plane et un principe différent de rétro-propagation, a été présentée. Cette méthode mieux prend en compte la propriété 2D de PSF, en décomposant la PSF dans un ensemble d'ondes planes directionnelle, les rétro-propage à la sonde, en utilisant les résultats de superposition comme excitations, un PSF simulée et conforme fortement au PSF théorique est acquis. En adaptant cette méthode à la géométrie sectorielle, la qualité de la PSF obtenue en face et sur la côté de la sonde est meilleure en utilisant la décomposition en ondes planes à celle de la transformée de Fourier, le travail supplémentaire sera adressé à adapter la décomposition en ondes planes à imagerie sectorielle et l’estimation du mouvementEchography is nowadays one of the most popular medical diagnosis modalities. It enables real-time observation the motion of moving organs which facilitates the diagnosis of pathologies for physician. Echocardiography [1, 2], blood flow imaging [3, 4] and elastography [5-7] are the favorite domains of motion estimation in using of echography (e.g., due to its high frame-rate capacity). Thus the requirements for imaging with high quality are on the primary place. In cardiac imaging, the conventional imaging system is somehow limited in the transverse direction (the direction perpendicular to the beam axis). Working on the image formation, this problem can be addressed by modifying the beamforming scheme in order to introduce transverse oscillations (TOs) in the system point spread function (PSF). Transverse oscillation techniques have shown their potential for improving the accuracy of local motion estimation in the transverse direction (i.e., the direction perpendicular to the beam axis). The conventional design of TOs in linear geometry, which is based on the Fraunhofer approximation, relates PSF and apodization function through a Fourier transform. Motivated by the adaptation of TOs in echocardiography, we propose a specific beamforming approach based on back-propagation in order to build TOs in sectorial geometry. The performance of the proposed back-propagation method has been studied gradually, in comparison with the Fourier transform, such as in evaluation of the quality of PSF, in estimation of simulated cardiac motion and in experiments study, etc. The quantified results demonstrate the proposed method leads to better controlled TOs images than the conventional beamforming. Another method based on plane wave decomposition and a different back-propagation principle has been presented. This method is better taking into account the 2D property of PSF, by decomposing the PSF into a set of plane waves directionally, back-propagating them to the probe, by using the superposition results as excitations, a simulated PSF with high accordance to the theoretical one is acquired. By adapting this method to sectorial geometry, the quality of PSF obtained in front of probe is better using the plane wave decomposition method than that of Fourier relation, but it is limited for the scanning on the side of probe, so the further work will be addressed to adapting the plane wave decomposition method to the complete sectorial imaging
14
McGinley, James W. "Real-time software-defined-radio implementation of a two source distributed beamformer." Worcester, Mass. : Worcester Polytechnic Institute, 2007. http://www.wpi.edu/Pubs/ETD/Available/etd-010807-213448.
Full text
15
Chen, Judy L. (Judy Lih-An) 1980. "The front end implementation of an audio beamformer for the RAW processor." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/87400.
Full text
16
Honarvar, Ali. "A low feedback robust opportunistic scheduler and beamformer for MISO wireless systems." Thesis, Kingston, Ont. : [s.n.], 2007. http://hdl.handle.net/1974/438.
Full text
17
Ponnekanti, S. "Efficient antenna based interference cancellation systems for narrowband and broadband signals." Thesis, University of Newcastle Upon Tyne, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282764.
Full text
18
Nybo, Jeffrey M. "Development of a GPU-Based Real-Time Interference Mitigating Beamformer for Radio Astronomy." BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/7749.
Full textAbstract:
Radio frequency interference (RFI) mitigation enables radio astronomical observation in frequency bands that are shared with many modern satellite and ground based devices by filtering out the interference in corrupted bands. The present work documents the development of a beamformer (spatial filter) equipped with RFI mitigation capabilities. The beamformer is intended for systems with antenna arrays designed for large bandwidths. Because array data post processing on large bandwidths would require massive memory space beyond feasible limits, there is a need for a RFI mitigation system capable of doing processing on the data as it arrives in real-time; storing only a data reduced result into long term memory. The real-time system is designed to be implemented on both the FLAG phased array feed (PAF) on the Green Bank telescope in West Virginia, as well as future radio astronomy projects. It will also serve as the anti-jamming component in communications applications developed for the United States office of naval research (ONR). Implemented on a graphical processing unit (GPU), this beamformer demonstrates a working single step filter using nVidia's CUDA technology, technology with high-speed parallelism that makes real-time RFI mitigation possible.
19
Khayeri, Parinaz. "Binaural Beamforming Robust to Errors in Direction of Arrival Estimates." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34442.
Full textAbstract:
Binaural beamforming technology, which is based on the auditory perception of both ears, uses a wireless data connection to exchange data between the right-side and the left-side hearing aids. Over the years, several multichannel speech enhancement algorithms have been used in the hearing aid industry. For example, beamforming algorithms work by keeping a target signal undistorted while attenuating the noise fields (such as diffuse noise or white noise) and the interferers from different directions. Fixed and adaptive algorithms of this nature have been under active investigation by the hearing aid industry. Although binaural beamforming hearing aids designs have shown better performance than single-channel based hearing aids or bilateral hearing aids, the performance of binaural beamforming still suffers from errors in the direction of arrival estimates, i.e., errors which occur when the right set of steering vectors is used in a beamformer design but the target signal source is not located at the direction considered in the design. Therefore, this thesis is devoted to find and propose structures showing more robustness to errors in the direction of arrival estimates. The focus is mainly on the Generalized Sidelobe Canceller (GSC) structure and several binaural beamforming algorithms and configurations are proposed in this thesis as alternatives for the fixed beamformer and blocking matrix units of the GSC. The proposed algorithms show promise of providing wider notch and/or wider beam possibilities, as well as providing greater noise reduction and superior adaptive null positioning capabilities. The algorithms proposed in this thesis were simulated in MATLAB using recorded signals and data provided by a hearing aid firm, to assess their utility for improving hearing aid performance. The results demonstrated a superiority over algorithms currently in use in industry.
20
Chen, Junying, and 陈俊颖. "Design space exploration of real-time bedside and portable medical ultrasound adaptive beamformer acceleration." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B50434354.
Full textAbstract:
This work explored the design considerations on the real-time medical ultrasound adaptive beamformer implementations using different computing platforms: CPU, GPU and FPGA. Adaptive beamforming has been well considered as an advanced solution for improving the image quality of medical ultrasound imaging machines. Although it provides promising improvements in lateral resolution, image contrast and imaging penetration depth, the use of adaptive beamforming is substantially more computationally demanding than conventional delay-and-sum beamformers. In order not to compromise the real-time performance of medical ultrasound systems, an accelerated solution is desirable.
In this work, CPU implementation was used as a baseline implementation, based on which the intrinsic characteristics of the algorithm were analyzed. After the analysis of a particular adaptive beamforming algorithm, minimum-variance adaptive beamforming, two design parameters M and L were found to affect the implementation performance in two aspects: computational demand and image quality. The trends of the two aspects were contradictory with respect to the increment of M and L values. In our experiments, when M and L increased, the computational demand increased in a cubic curve; meanwhile, the image quality did not have much improvement when the increased values of M and L entered certain ranges. Since we targeted at a real-time solution without sacrificing the good image quality that adaptive beamforming proposed, a tradeoff was made on the selection of M and L values to balance the two contradictory requirements.
Built upon the theoretical algorithmic analysis of the real-time adaptive beamformer realization, the implementations were developed with FPGA and GPU. While a dedicated hardware solution might be able to address the computational demand of the particular design, the need for an efficient algorithm exploration framework demanded a reprogrammable platform solution that was high-performance and easily reconfigurable. Besides, although a simple processor could provide convenient algorithm exploration via software development environment, real-time performance was usually not achievable. As a result, a reprogrammable medical ultrasound research platform for investigating advanced imaging algorithms was constructed in our project. The use of FPGA and GPU for implementing the real-time adaptive beamformer on our platform was explored. In our test cases, both FPGA- and GPUbased solutions achieved real-time throughput exceeding 80 frames-per-second, and over 38x improvement when compared to our baseline CPU implementation.
Moreover, the implementations were also evaluated in terms of portability, data accuracy, programmability, and system integration. Due to its high power consumption, high-performance GPU solution is best suited for bedside applications, while FPGAs are more suitable for portable and hand-held medical ultrasound machines. Besides, while the development time on GPU platform remains much lower than its FPGA counterpart, the FPGA solution is effective in providing the necessary I/O bandwidth to enable an end-to-end real-time reconfigurable medical ultrasound image formation system.published_or_final_version
Electrical and Electronic Engineering
Doctoral
Doctor of Philosophy
21
Mousa, Pasandi Mohammad Ebrahim. "Implementation of Radio-Over-Fiber OFDM System Including a Novel Optical Null-Steering Beamformer." Thesis, Université Laval, 2008. http://www.theses.ulaval.ca/2008/25825/25825.pdf.
Full text
22
Wilkins, Nathan Allen. "Signal Subspace Processing in the Beam Space of a True Time Delay Beamformer Bank." Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1433034139.
Full text
23
THUPALLI, NAVEEN KUMAR. "MICROPHONE ARRAY SYSTEM FOR SPEECH ENHANCEMENT IN LAPTOPS." Thesis, Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-2593.
Full textAbstract:
Recognition of speech at the receiver end generally gets degraded in distant talking atmospheres of laptops, teleconfereing, video conferences and in hands free telephony, where the quality of speech gets contaminated and severely disturbed because of the additive noises. To make useful and effective, the exact speech signals has to be extracted from the noise signals and the user has to be given the clean speech. In such conditions the convenience of microphone array has been preferred as a means of civilizing the quality of arrested signals. A consequential growth in laptop technology and microphone array processing have made possible to improve intelligibility of speech while communication. So this contention target on reducing the additive noises from the original speech, beside design and use of different algorithms. In this thesis a multi-channel microphone array with its speech enhancement of signals to Wiener Beamformar and Generalized side lobe canceller (GSC) are used for Laptops in a noisy environment. Systems prescribed above were implemented, processed and evaluated on a computer using Mat lab considering SNR, SNRI as the main objective of quality measures. Systems were tested with two speech signals, among which one is Main speech signal and other is considered as Noise along with another random noise, sampling them at 16 KHz .Three Different source originations were taken into consideration with different input SNR’s of 0dB, 5dB, 10dB, 15dB, 20dB, 25dB. Simulation Results showed that Noise is been attenuated to a great extent. But Variations in SNR and SNRI has been observed, because of the different point origination of signals in the respective feilds.Variation in SNR and SNRI is been observed when the distance between the main speech originating point and microphone is too long compared to the noise signals. This states that origination of signals plays a huge role in maintaining the speech quality at the receiver end.D.No 4-22, Gandla street, papanaidupeta-517526 chittoor district,Andhra pradesh India naveenkumarthupalli@gmail.com
24
Rauch, Barbara [Verfasser], and Dietrich [Akademischer Betreuer] Klakow. "Modelling the nonstationarity of speech in the maximum negentropy beamformer / Barbara Rauch. Betreuer: Dietrich Klakow." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2011. http://d-nb.info/1051056616/34.
Full text
25
Coleman, Thomas Christopher. "An Assurance Metric and Robustness Evaluation of a Low-cost Acoustic Beamformer for Source Localization." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/84418.
Full textAbstract:
A rise in interest for service robotic rovers produces a need for a low-cost method for source localization in order for a prospective robotic unit to engage with a human operator. This study examines the use of the LMS algorithm for constructing a beamformer using an optimized Weiner filter solution for this source localization application and evaluates the robustness of a developed characterization method for assuring that a proper approximation for the desired signal is achieved. The method presented in this paper encompasses using a filter and sum method in which the sums are generated for a selected set of filter angles, and this set of sums are compared and characterized to produce a selection for an approximate arrival angle from the sound source to the microphone array. These filters are adaptively trained offline using a generated desired signal chirp to represent the average human whistle and a training data set for each of the four possible room configurations. This method was tested to determine if a selected filter configuration could still produce viable outputs for scenarios in which the testing room had been changed, whether noise was injected into the testing environment, if two or three microphones were used in testing process, and whether the filter angles are aligned with the arrival angles of the signal. Results on the robustness of the adaptive LMS beamformer are presented. Limitations of the system performance are discussed and possible solutions for results that have undesired performance are given in future work.Master of Science
26
Caulk, Jeffrey V. "Experimental and theoretical performance of a particle velocity vector sensor in a hybrid acoustic beamformer." Thesis, Monterey, California : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/theses/2009/Dec/09Dec%5FCaulk.pdf.
Full textAbstract:
Thesis (M.S. in Engineering Acoustics)--Naval Postgraduate School, December 2009.Thesis Advisor(s): Kapolka, Daphne ; Smith, Kevin B. "December 2009." Description based on title screen as viewed on January 29, 2010. Author(s) subject terms: Particle velocity, beamforming, beam pattern, acoustic array, acoustic vector sensor, Microflown, hybrid array, frequency spectrum, linear array, directional. Includes bibliographical references (p. 151-153). Also available in print.
27
Ruzindana, Mark William. "Digital Signal Processing Algorithms Implemented on Graphics Processing Units and Software Development for Phased Array Receiver Systems." BYU ScholarsArchive, 2021. https://scholarsarchive.byu.edu/etd/8987.
Full textAbstract:
Phased array receivers are a set of antenna elements that are capable of forming multiple simultaneous beams over a field of view. In radio astronomy, the study of deep space radio sources, a phased array feed (PAF) is placed at the focus of a large dish telescope that spatially samples the focal plane. PAFs provide an increase in the field of view as compared to the traditional single pixel horn feed, thereby increasing survey speed while maintaining low sensitivity. Phased arrays are also capable of radio frequency interference (RFI) mitigation which is useful in both radio astronomy and wireless communications when detecting signals in the presence of interferers such as satellites. Digital signal processing algorithms are used to process and analyze data provided by phased array receivers. During the commissioning of the Focal-plane L-band Array feed for the Green Bank telescope (FLAG), sensitivity consistent with an equivalent system temperature below 18 K was measured. To demonstrate the astronomical capability of the receiver, a pulsar (PSR B2011+38) was detected, and an HI source (NGC4258) was mapped with the real-time beamformer and fine channel correlator, respectively. This work also details improvements made to the software of the FLAG digital backend such as the design and implementation of an algorithm to remove scalloping ripple from the spectrum of two cascading polyphase filter banks (PFB). This work will also provide a brief introduction to a model-based beam interpolation algorithm capable of increasing spatial resolution of radio source maps as well as reducing time spent performing calibration. The development of a phased array receiver digital back end for the Office of Naval Research (ONR) is also detailed. This broadband system will be capable of communication in hostile RFI-rich environments with the aid of a real-time RFI mitigation algorithm currently implemented in software. This algorithm will be compatible with other PAF receiver systems and will enable RFI mitigation in other applications such as radio astronomy. This work will provide details on the implementation of this algorithm, the development and modification of other system software as well as full system tests of the 150 MHz bandwidth receiver have been conducted and will be shown in this document.
28
Liu, Wei Han, and 劉維瀚. "Multiple Constraint LMS Beamformer." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/21876412836631690052.
Full textAbstract:
碩士國立交通大學
電機與控制工程系
90
In this thesis, a multiple constraint LMS beamformer algorithm is proposed for wideband beam steering. The algorithm combines the traditional Frost beamformer algorithm and optimal fractional delay filter design technique so that multiple beams or nulls can be formed in arbitrarily assigned directions. Because of the null constraint, the proposed algorithm can avoid the desired signal cancellation effect caused by coherent sources in the Frost beamformer algorithm. This thesis is divided into three parts. In the first part, a brief introduction to array signal processing is presented. In the second part, the proposed algorithm is analyzed and the limitation is discussed. Simulations are conducted and the performance is compared with Frost beamformer in the third part. It is shown that the spatial filtering result is much better than Frost Beamformer when coherent sources appear in received signals.
29
Cai, Sing-Jhang, and 蔡幸璋. "Isolation Improvement of Beamformer Design." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/4w4h5r.
Full textAbstract:
碩士國立中正大學
電機工程研究所
103
Isolation improvement for phased array antenna and active phase shifter using TSMC CMOS 0.18μm technology are represented in this thesis. The first subject is an phased antenna array inserting slotted meander line resonator (SMLR) and parallel-coupled feed (PCF) for isolation enhancement and then comparing the effects of SMLR with PCF. The phased array antenna in this study constitute of three circuits that are 1x2 array antenna with isolating elements, delay line phase shifter and Wilkinson power divider, respectively. Each section of the phased array antenna is implemented on Arlon 25N substrate. Array antenna using PCF is a new method proposed in this thesis for isolation enhancement. PCF is an open circuit at one end and short circuit at the other end by the grounding via and inserted aside the feed line of antennas. Assume coupled current signals from adjacent antenna that flow through feed line toward the port of coupled antenna and then coupled to PCF nearby, finally, the current signals flow through the via to the ground plane. Therefore, the coupled current signals flowing toward the port of coupled antenna would be diminished, then isolation of array antenna is enhanced. The second subject is active reflective type phase shifter. The design concept comes from the reflective type phase shifter (RTPS). Nevertheless, RTPS occupies too large area especially below an operational frequency of 20 GHz. The proposed active phase shifter is nearly symmetric, low power consumption and occupies less chip area by replacing spiral inductors with active inductors.
30
Chou, Zane E., and 冉一喬. "Cumulant-Based Adaptive Blind Beamformer." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/19636698632395942809.
Full textAbstract:
碩士國立海洋大學
電機工程學系
87
Abstract A beamformer is a processor used in conjunction with an array of sensors to provide a versatile form of spatial filtering. A beamformer performs spatial filtering to separate signals that have overlapping frequency content but originate different spatial locations .Thus, beamformer has been widely applied in the radar, sonar and communication field. In most optimum beamforming procedure(see Chapter 2), they rely on complete knowledge of response and location or array elements and/or DOA information of the desired signal. If the array manifold is unknown, or they are uncertainities , it is then necessary to calibrate the array. In addition, calibration source may be required. Even small errors in the calibration may considerably degrade the performance. We employ the higher older statistical characteristics of the desired signal to make the discrimination ,without any a-priori knowledge of array manifold and DOA information about desired signal .In a communications environment, multipath propagation almost take place. In this case, most conventional techniques fail ,but cumulant-based beamformer still behave as the optimum beamformer. In our work, we not only describe blind estimation and optimum narrowband/broadband beamforming but have some simulations for different conditions. For real-time operation ( a necessary requirement in communications applications ) we also propose adaptive implementations of the cumulant-based beamformer for narrowband and broadband environment .
31
Tasi, Ho-Shun, and 蔡和矄. "Firmware Implementation of Blind Adaptive Beamformer." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/38659847472714334249.
Full textAbstract:
碩士國立海洋大學
電機工程學系
89
When acoustic waves propagate across underwater channel, signals are severely distorted due to environmental factors and turbulent waves. In general, computer simulations are mostly performed in research papers for analysis of signals distorted by channel effects. However, the fact that realistic channels are much complicated and time-varing makes feasibility of simulation doubtfuland needs to be verified. In this thesis, firmware for recently proposed blind adaptive beamformer is developed and verified by experiments with water trough. C3X DSK is used for firmware realization of the beamformer. Experimental results have shown the effectiveness of the beamformer. Using cyclostationarity of communication signals,the blind adaptive beamformer has the following advantages over MVDR beamformer: 1)The incident angle of desired signal is not required; 2) The fading effect of multipath can be improved effectively: 3)Performance is insensitive to the position error among the sensors. Keywords：underwater channel, channel effect, beamformer, cyclostationarity, blind, adaptive
32
Huang, Chen-June, and 黃呈俊. "The Research of Parallel Adaptive Beamformer." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/57659747794697501687.
Full textAbstract:
碩士國立海洋大學
電子工程學系
81
Adaptive beamformer has been widely used in military or industrial applications,such as radar, sonar, underwater communication and geophysical exploration, etc. Apart from having to meet the requirements of real-time signal processing, in actual applications the adaptive beamformer must also overcome various types of adverse environmental factors. This often results in serious degradation of the array performance. Other important issues include the problems of coherent interference and pointing error, both of which have attracted intensive research. Coherent interference are generally caused by multipath transmission or active jammer. On the other hand, pointing error is caused by error in target signal direction estimation. Along with the advancement of VLSI technologies, some of the common algorithms for signal processing can now be implemented as highly pipelined and regular systolic arrays. Consequently, the performance level necessary for real-time processing can be realized. This thesis adopts a QR systolic array as the computational engine and uses the GSC adaptive beamformer as the underlying architecture featuring a simple hard preprocessor. The beamforming techniques we have proposed include two parallel adaptive beamformers, namely, the modified data-domain parallel spatial processing scheme (MDPSP), and the modified data- domain parallel spatial smoothing scheme (MDPSS). Both are effective in cancelling the coherent interference while alleviating the adverse effect caused by the pointing errors. Moreover, they converge fast and need only a very small amount of sampling data for completing the adaptive process. The results gathered from the computer simulations have shown that the performances of the proposed structures are very satisfactory.
33
潘長永. "Beamformer design using two-dimensional rectangular array." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/55847551169076743609.
Full textAbstract:
碩士國立海洋大學
電機工程學系
90
1-D uniform linear array (ULA) beamformer would cause a conical ambiguity surface, and the beamformer would be aliased by the propagating signals coming from this conical surface. Therefore in this thesis, we are not only using 1-D ULA to design the beamformer but also using the 2-D rectangular array to overcome the problem. For wideband signal processing, most focussing algorithms require preliminary estimate of the source angle resulting in the estimation bias. In this thesis, we adopt signal subspace focussing (SSF) method to design a wideband beamformer to omit preliminary estimate of the source angle. Finally, we adopt the column vector focusing method to design the wideband beamformer. Using this method, we can avoid the eigenvalue decomposition when estimate the signal subspace in SSF is estimated, therefore reducing the computational complexity.
34
張重勝. "Research of adaptive arrays for beamformer application." Thesis, 1990. http://ndltd.ncl.edu.tw/handle/79183223033470635565.
Full text
35
CHEN, BANG-HUANG, and 陳邦皇. "Realization of adaptive beamformer using microprogramming approach." Thesis, 1989. http://ndltd.ncl.edu.tw/handle/15363431974047486275.
Full text
36
Kuo, Tang-Yen, and 郭唐巖. "Design of Two-Dimensional Wide-band Beamformer." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/43601443708608849422.
Full textAbstract:
碩士國立臺灣海洋大學
電機工程學系
93
Beamformer is a spatial filter based on a sensor array. Its main function is to suppress the interference signals as well as to restore the desired signal. For wide-band signals, early-stage signal processing methods using focusing schemes require preliminary direction-of-arrival (DOA) estimate, thus resulting in performance sensitive to the estimation errors. In the thesis, we first adopt the signal subspace focusing method to design a two-dimensional wide-band beamformer, which does not require preliminary DOA estimation. But eigenvalue decomposition in each frequency bin as required for each signal subspace needs great computational burden. Therefore, we investigate a two-dimensional wide-band MVDR beamformer based on spatial resampling algorithm. This method is to first use interpolation to focus each signal’s direction vector at various frequencies onto its direction vector at some focusing frequency and then use MVDR algorithm for beamforming. It significantly reduces the computational complexity at the expense of slightly worse resolution. For performance evaluation and comparison, computer simulations and underwater acoustic experimentations in a lab tank were carried out. Keywords : wide-band beamformer, two-dimensional rectangular array , spatial resampling, focusing matrix, MVDR.
37
Wei, Yung-Ming, and 魏永銘. "Adaptive Beamformer Design via Inverse QR Decomposition." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/19395716074143589336.
Full textAbstract:
碩士國立海洋大學
電機工程學系
91
Beamformer has been widely applied to radar, sonar as well as underwater and land wireless communications. If we want to implement the beamformer algorithms based on DSP chips,lower computational complexity, higher numerical stability and faster convergence speed are the most crucial concerns. The thesis is divided into two parts in order to discuss the beamformer algorithms. Part 1:The suppression method of the baseband interference signal. We use the beamformer based on linear constraints to suppress interference signal. Part 2:The suppression method of the bandpass interference signal. We use the blind adaptive beamformer that does not require to know the incident angle and the steering vector of the desired signal, thus the calibration procedure of a sensor array can be omitted. In order to achieve the real time processing via DSP chips, we adopt the recursive least square(RLS) algorithm based on inverse QR decomposition(IQRD-RLS).The advantages include not only the higher numerical stability and the lower computational complexity,but also the parallel processing capability makes the implementation of specific DSP chip feasible.
38
Ren, Chen Jau, and 陳昭仁. "Design of All-Digital Blind Adaptive Beamformer." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/14486902347260675224.
Full textAbstract:
碩士國立海洋大學
電機工程學系
89
In the conventional lowpass theory, the sampling rate must be twice higher than the largest frequency of a low-pass signal. Therefore, the sampling rate would be largely increased for a band-pass signal with higher carrier frequency. In this thesis, the bandpass sampling principle is employed to design an all-digital blind adaptive beamformer, which directly takes samples from a bandpass signal, effectively reduces the sampling rate of Analog-to-Digital Converter, and increases the feasibility of firmware implementation. In practical applications, position errors due to hydrophone array deployment or environmental factors, such as wind and turbulent waves, as well as pointing error of the desired signal source can detrimentally affect beamformer''s performance. We investigate the performances of three types of beamformers, i.e. blind, delay sum (DS), and Frost, under position or pointing error by computer simulations. Simulation results have shown that the all-digital blind adaptive beamformer is able to effectively reduce noise and interfering signals. Finally, using the data measured in water trough by computer off-line analysis, the feasibility of the blind beamformer is verified.
39
Huang, Chin-Tien, and 黃進添. "The Research of Householder Transformation Systolic Beamformer." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/23383137489294311649.
Full textAbstract:
碩士國立海洋大學
電子工程學系
82
Householder transformation is a data-adaptive transformation which enjoys widespread popularity in modern numerical analysis. In signal processing field, it is desirable to find a fast and stable algorithm that satisfies the demand of matrix computations and the requirement of real-time processing. Householder trans- formation is numerically very stable , especially , for the application of adaptive algorithms. This thesis introduces a stable and highly efficient systolic algorithm. It is regular, recursive, highly pipelined, and possesses communication locality. It can also acheive the goal of real-time signal processing with parallel implementation. These properties can be exploited in developing VLSI parallel/pipelined architectures. Adaptive beamformer has been widely used in military and industrial applications such as radar, sonar, underwater communi- cation , geophysical explorations , etc. This thesis adopts a Householder transformation QR-RLS systolic array as the compu- tational engine and uses the GSC adaptive beamformer as the underlying architecture. The system proposed is a Householder transformation systolic beamformer. This modified architecture is effective in cancelling the interference and noise ; it also converges fast and needs only a very small amount of sampling data.The results gathered from thecomputer simulations have shown that the performance of Householder transformation systolic beamformer is very satisfactory.
40
Hsu, Guan-Wen, and 許冠文. "Beamformer Design for Multicell Multigroup Multicast Systems." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/34107916748819456927.
Full textAbstract:
博士國立臺灣大學
電信工程學研究所
104
This dissertation considers a beamforming design problem in the Multicast Broadcast Single Frequency Network (MBSFN) scenario with multiple multicast groups that provide different multicast services. In the first part of this work, we devise different kinds of optimization techniques such as semidefinite relaxation, fractional program and difference of convex (DC) program to solve the joint beamforming design among the cooperating base stations (BSs), which is also known as the joint processing (JP) scheme in coordinated multipoint transmission (CoMP) defined in the Long-Term Evolution-Advanced (LTE-A) system. In the second part, we consider a more general scenario that each user is equipped with multiple receiving antennas. Therein, we propose a heuristic algorithm based on the downlink-uplink (DL-UL) duality structure to resolve the joint beamforming problem. Throughout the work, per-cell power constraints are considered. In addition, we consider the design of higher rank transmission to increase the spectrum efficiency, and the design of robust beamforming to alleviate performance degradation caused by imperfect channel state information. In the simulation results, we demonstrate the potential of the proposed algorithms in terms of the maximized minimum signal to interference plus noise ratio (SINR), and compare the proposed methods with the traditional MBSFN transmission scheme and the existing non-cooperating multicast beamforming methods. The results show that the proposed methods indeed provide better performance. We also provide numerical results of the robust and non-robust beamforming schemes in terms of the power consumption, feasibility ratio, and the histogram of the normalized SINR to complete the discussion.
41
Byun, Jong-Min. "Artificial neural network system for array beamformer." 1991. http://catalog.hathitrust.org/api/volumes/oclc/24487340.html.
Full textAbstract:
Thesis (M.S.)--University of Wisconsin--Madison, 1991.Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 21-22).
42
Chen, Hsuan-Ling, and 陳玄齡. "Application of Adaptive Beamformer to Mobile Communications." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/78522383093429579593.
Full textAbstract:
碩士國立海洋大學
電機工程學系
85
The mobile radio channel is different from the white Gaussian channel due to the property of time varying impulse response. Both the channels of mobile cellular network and Global Positioning System have this kind of feature, so that the mobile radio channel model should be constructed to evaluate the system performance and availability. Underwater acoustic channel has similar characteristics, thus by adding factors and modifying certain factors, an underwater channel model can be constructed. Beamformer has the ability to depress interference and recover desired signal. Thus, beamformer has been widely applied in the fields of radar, sonar and communication. The purpose of this thesis is to study the land and underwater mobile channel models, and examine the performance of Frost beamformer under the land mobile channel. Simulation results show that Frost beamformer still can de press, to some extent, interference and Gaussian noise to obtain lower bit error rate of desired signal, although its performance degrades due to signal fading of channels. In this thesis, a TMS320C30 digital signal processor, produced by Texas Instruments, is used to implement the hardware system of Frost beamformer for real-time of processing. Finally, this hardware system is examined in the underwater environment to evaluate its performance.
43
Chao, Hung-Chieh, and 趙宏傑. "Development of therapeutic ultrasound phased-array beamformer." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/t2uy25.
Full textAbstract:
碩士國立交通大學
生醫工程研究所
106
At present, the treatment of tumor is mainly taken out after anesthesia, or combined with radiation and chemical treatment. The process takes a long time and can result in wounds and complications associated with radiation and chemotherapy. High-intensity focused ultrasound (HIFU) has high energy and focusing characteristics, which can achieve the thermal effect or hole effect of local tissue in a short time. HIFU can be used to cauterize/ablate tumor cells and achieve the purpose of tumor treatment. In addition, HIFU is a noninvasive, low-side-effect treatment that does not require hospitalization. And, the pulse signal is supplied to multiple elements of the HIFU array through the power amplifier. By tuning the phase of each element, ultrasound waves converges on the small region at focus, and focal tissue is ablated thermally. In order to realize the dynamic focusing of HIFU phase array transducer, the purpose of this paper is to develop a set of multi-channel beam forming device. An HIFU transducer with 256 elements was taken as an example. The dimensions of the transducer were calculated first, and the coordinate of each element was expressed in terms of the cylindrical coordinate system. Based on the time-delay theory, the phase of each element was obtained. The LabVIEW was used for phase calculation.
44
Fang, Wei-Ting, and 方偉廷. "Miniaturized switched beamformer module using bridged-T coils." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/95779107255792422064.
Full textAbstract:
博士國立中央大學
電機工程學系
105
Phased arrays have been gradually applied to wireless communication systems in our daily life. Among various phased array technologies, the switched beamformers are relatively easy to realize, and they are more suitable for commercial wireless communication systems due to their low power consumption and low cost. In this study, two 2.4-GHz switched beamformer modules in IPD process with low power consumption and compact size are proposed, which are targeted for implementing smart antenna systems in mobile communication devices. The Bridged-T coil is the core technology used in this study. Specifically, the bridged-T coil is adopted to realize the building blocks of the proposed switched beamformer such that very compact circuit size can be achieved. The use of the bridged-T coil to achieve circuit size reduction of microwave circuits is first demonstrated by an ultra-wideband multi-mode resonator bandpass filter design. The smallest multi-mode resonator bandpass filter ever reported is presented. Next, the bridged-T coils are used to realize the key building blocks of a 2.4-GHz switched beamformer modules, i.e., an absorptive single-pole double-throw (SPDT) switch, a T/R switch, and a 4 × 4 Butler matrix. By replacing the transmission line sections with bridged-T coils, the chip sizes of these circuit elements are largely reduced. Two switched beamformer modules are then realized based on the heterogeneous integration of these building blocks. The first one integrates a 4 × 4 Butler matrix, an absorptive SP4T switch, and a T/R switch in a compact module size of 4.9 mm × 5.0 mm ×0.9 mm. The second one integrates a 4 × 4 Butler matrix and two absorptive SPDT switches, which features a module size of 4.9 mm × 5.0 mm with a very low profile of only 0.4 mm. In additional, dual-band bridged-T coil is proposed to help achieve miniature dual-band beamformer designs. A dual-band branch-coupler is first implemented in IPD process, which is the smallest dual-band branch-line coupler ever reported. Then, a dual-band 4 × 4 Butler matrix is designed for 2.45/5.8-GHz dual-band switched beamformer applications. The proposed switched beamformer modules feature low-cost, compact size, low power consumption, and low-profile. They can help introduce smart antenna systems into modern mobile applications.
45
Niezgoda, George Henry. "A multiple time-scale linearly constrained adaptive beamformer." Thesis, 1994. http://spectrum.library.concordia.ca/4584/1/NN90922.pdf.
Full text
46
Huang, Jing-Jung, and 黃景忠. "Beamformer Design for a Digital Ultrasonic Imaging System." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/74316697247196967408.
Full textAbstract:
碩士國立臺灣大學
電機工程學研究所
89
The beamformer is one of the most complicated units in an ultrasound array imaging system. To optimize image quality, dynamic receive focusing is required. Dynamic focusing involves extensive real-time computations and thus the system cost and size can not be reduced unless major redesign of the system is implemented. It is the main purpose of this thesis to explore new design strategies such that complexity of the receiver can be reduced without sacrificing image quality. The thesis consists of three main components: (I) A new delta-sigma based beamformer is proposed. The new system reduces complexity, size, and cost while maintaining a sufficient signal-to-noise ratio due to the single-bit architecture. A well-known problem in delta-sigma based beamformers is that the system introduces noises during dynamic focusing. Several approaches were proposed to solve this problem at the price of some advantages of delta-sigma modulators. The new method proposed in this thesis is based on the symmetry of focusing using an array transducer. By proper delay-control and selection of the inserted samples during dynamic focusing, no additional noise is added to the beamforming results and the image background level is not increased. Using real ultrasound data, it is shown that the technique offers image quality comparable to a conventional system. (II) Sound velocity inhomogeneities in the human body produce phase aberrations and degrade image quality. The delta-sigma based beamformer can also be used to correct the aberrations using a correlated-based approach. Results show that the performance is equivalent to the same approach implemented in a conventional system with a greatly simplified system architecture. The different dynamic focusing control schemes discussed in part (I) are also studied in the context of phase aberration correction. It is shown that the delta-sigma based single bit dynamic focusing approach does not affect the overall performance of phase aberration correction. (III) The third topic is the investigation of dynamic focusing using 2-D arrays. The dynamic focusing architecture becomes more complicated when a 2-D array is used for real-time 3-D imaging. Size and cost of the receiving beamformer becomes enormous if conventional methods are used. In this thesis, a new technique utilizing the spatial and value characteristics of the focusing delay pattern is proposed. It is shown that grouping of delay-change-patterns can reduce the number of delay controllers, and non-uniform quantization of delay-change-patterns can simplify the delay control architecture. Simulation results show that dynamic focusing can be implemented using a simple architecture with a slight degradation in the near field focusing quality. It is the conclusion of the thesis that the various beamforming architectures proposed in this thesis can be used for size and cost reduction of a digital imaging system, adaptive imaging and real-time 3-D imaging using 2-D arrays. An ASIC-design of the delay controller is also included in the appendix.
47
Chang, Chuan-Liang, and 張全良. "The Wavelet-Based Spatial Processing Technique Adaptive Beamformer." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/22438130552696134840.
Full textAbstract:
碩士國立海洋大學
電機工程學系
84
Wavelet function performs not solely a new basis of function, it formsa collection of flexible windows in the time-scale plane with the dilation andtranslation of basis wavelet function. Its filtering effect in the frequencydomain does agree the constant- Q theorem. That is, the filtering effectmaintains identical in arbitrary range of frequency band.Thus, this improves thetraditional fourier transform which falls into failure to analyzing theinstantaneous frequency of non-stationary signal whose frequency istime-varying. In addition, it also remedies the problem of unequal dataextraction of short time fourier transform (STFT)in the analysis of signal no matter high and low frequencies. Asa result, we can conclude that wavelet transform to be one of the good toolsin the time-frequency analysis. By its application on the least meansquare (LMS) algorithm, an orthogonal wavelet-domain transformed signalcan be obtained from time-domain input signal with the multiresolutionof wavelet transform. The eigenspread of input signal correlation matrixcan be reduced, therefore, the convergence speed of the wavelet- domainleast mean square (WLMS) learning curve is enhanced. In consequence,the objective of speeding up the system operation is achieved.This thesis intends to apply the specification mentioned aboveon the traditionalGSC framework adaptive beamformer in order to improve its algorithm part.The WLMS algorithm is also utilized expect to forcesystems achieving their stability in faster order, simultaneously, interferenceis suppressed and target signal is received accurately . For coherentinterference that awaked by multi-path or electronics warfare, theremedy can be reached by constructing WASPAB fromparallelized adaptive beamformer thatdeveloped with the application of spatial smoothing and parallel spatialprocessing technique, in addition, with the algorithm improvement carriedby wavelet transform. The weight adjustment speed can be increaseto enhance the performance of traditional adaptive beamformer, at the sametime, the problem of coherent interference is also solved.
48
LIU, CHIH-SHIAO, and 劉志曉. "Blind Broadband Beamformer Design Using Higher Order Cumulants." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/91745909798069162950.
Full textAbstract:
碩士國立海洋大學
電機工程學系
84
Beamformer has the ability to depress the jammer and recover the desiredsignal. Thus, beamformer has been widely applied in the radar, sonar and communication field. The beamformer required accurate Direction-of-Arrival(DOA) and array manifold to evaluate the steering vector. During practical application, the above mentioned information is not easily obtained. Other attendant processes are needed to obtained the required information. The influence of doubtful DOA and uncertain responses and locations of array elements would reduce the performance of beamformer. In recent years, higher-order cumulants are widely applied as signal processing tools. By using higher-order statistics, more signal information can be retrieved. In this paper, study on the application of beamformer based on higher-order cumulants are conducted. Due to the lack of arraymanifold related information and DOA of desired signal, by using thehigher-order cumulants, the steering vector of the desired signal can be calculated. This would reduce the error caused by doubtful DOA and uncertainarray manifold. Keywords : beamformer, DOA, steering vector, higher-order cumulants
49
Liang, Ming Cheng, and 梁明正. "The Performace Error Analysis of Partial Adaptive Beamformer." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/93914203354841600337.
Full textAbstract:
碩士國立中山大學
電機工程研究所
82
Adaptive antenna array could decay interferences power well , if the total interferences power is more greater than desired signal power. And that, if the interferences power are more large , it will decay the interference more. So that, adaptive antenna array is well applicated in sonar, radar and so on. When the dimension of adaptive weights is large, the amount of calculation is increased rapidly. It results in that adaptive antenna array can't perform well on real time. So that, many kinds of partially adaptive beamformer have been proposed. Van Veen have proposed an method 'eigenstructure base partially adaptive array ' to reduce the adaptive weight dimension. The method is that extract the major signal subspaces from correlation matrix of input data vector to be the reduce order matrix. In this text, we will analyze the partially adaptive beamformer when some errors occur. These errors include steering vector error, weight vector error and constrain angle bias. We will discuss how to choose the adaptive weight dimension properly, when these errors occur. In these analysis, we also find that choosing the dimension properly not only reduces the amount of calculations but also increases the robust of antenna for some error.
50
陳乙慈. "Beamformer-based Spatiotemporal Imaging of Correlated Brain Activities." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/46285801997275093544.
Full textAbstract:
碩士國立交通大學
多媒體工程研究所
97
It has been widely accepted that neurons in the human brain collectively have synchronous patterns of activities. The past findings have suggested that temporal correlation may relate to the communications between the distributed areas. There are some studies in magnetoencephalography and electroencephalography that analyze the functional connectivity between cortical areas using the oscillatory features of neuronal activity. However, temporal dynamics of neuronal activities is generally consisted of cross-frequency components. Therefore, it is also important to directly investigate the functional connectivity as well as general synchronization. In this thesis, we have proposed a beamformer-based imaging method of correlated brain activities that can reveal the neural network with similar temporal patterns for information exchange. The method can identify the correlation distribution referred to a specified position, called the reference region. In principle, we can apply our method on all pairs of grid points to identify all possible neural networks of correlated activities. Our method exploits a maximum-correlation criterion that maximizes the significant level of correlation between the reference region and the entire brain volume. The maximum correlation criterion helps to analytically and accurately determine the dipole orientation in a closed-form manner and thus determine the spatial filter very efficiently for each position. The correlation map can be calculated to reveal cortical regions with significant similarity to the reference position in the brain. The experiments with simulation data demonstrated that our method can accurately determine the correlated regions. Different from the conventional source localization method, we focus on the areas which have the similar temporal patterns with the reference signal. We demonstrated the applicability of the proposed method on real data. In the mirror neuron experiment, most of the regions we revealed are reported by the previous findings of emotional processing, face perception and the mirror neuron system. Moreover, we can provide the time information about when these regions are correlated to the neural network. In summary, the proposed method can be used to directly study dynamics of correlation brain areas based on electromagnetic recordings of brain activities. Given the reference region as one of the areas in the neural network, our method can estimate the correlated regions at each time point and thus reveal the dynamic behavior of the neural network.