Approved for public release; distribution is unlimited / The MiniCan hydrophone is a small, easy to build, preamplified hydrophone with similar characteristics in sensitivity and self noise to larger and more expensive commercial devices. Previous work on the design showed a very promising performance, though it proved to have a flat sensitivity response of only up to 14 kHz. Unknown were also the effects that the aluminum housing parts produced on the overall response and whether the cable of the hydrophone had some influence on the sensitivity. A new design was built and tested changing the dimensions of the aluminum housing for the hydrophone, resulting in an increase in the region of flat sensitivity response up to 20 kHz and acceptable response up to 30 kHz, due to an increase of the lowest mechanical resonance of the hydrophone. A resonance testing device was built to investigate the mechanical characteristic of the components of the design, discovering that the first resonance of the aluminum base of 34.6 kHz caused the first overall resonance of the assembled device. Measurements of the influence of the cable showed an acoustic variation of about 1 dB in relative response in the range of interest, which is up to 30 kHz. The measurements proved that better performance can be achieved on the basic MiniCan design by increasing the resonant frequency of the aluminum body housing component. / Lieutenant, Chilean Navy

This pro ject summarizes the design and implementation of field programmable gate array (FPGA) based digital signal processing (DSP) hardware meant to be used in a software radio system. The filters and processing were first designed in MATLAB and then implemented using very high speed integrated circuit hardware description language (VHDL). Since this hardware is meant for a software radio system, making the hardware flexible was the main design goal. Flexibility in the FPGA design was reached using VHDL generics and generate for loops. The hardware was verified using MATLAB generated signals as stimulus to the VHDL design and comparing the VHDL output with the corresponding MATLAB calculated signal. Using this verification method, the VHDL design was verified post place and route (PAR) on several different Virtex family FPGAs.

In this graduation thesis it is deduced deformation and tightness of leg’s receiver as well as skin and soft tissues’ at contact place. By using the finite elements method with digital ANSYS 5.5.1 programmable packet it was made leg��s prothesis receiver and stump soft tissues’ model. Two models were analysed: linear and non-linear. By making the non-linear system calculation it is measured non-linear features of leg’s prothesis receiver material and stump skin soft tissues’. Results of analyses showed that the size of maximum deformation is 1,3 less then in case of linear system, maximum stress decreases 1,2 times. Consequently for exact contact calculation it is needed to use non-linear model.

In Multi-Standard receivers, multiple radios co-exist in close proximity. A desired signal can be accompanied by significantly stronger out-of band interferers or blockers, which can severely degrade a receiver's sensitivity through gain compression of the blocks in the receiver chain. This work presents a new Transimpedance Amplifier (TIA) low-pass filter architecture which seeks to solve the out-of-band blocker problem of the existing architectures. A higher order filtering is embedded within the TIA in the form of an active feedback to provide more attenuation to out-of-band blockers. The active feedback circuitry feeds back an equivalent amount of current to the input node to cancel out incoming out-of-band blockers while maintaining an acceptable voltage swing at the output of the TIA. The proposed TIA filter has a channel bandwidth of 20MHz, and can processes interferers of +/- 10mA fully differential without saturating the opamps. The maximum single ended voltage swing at all the nodes is +/- 200mV. All the circuits were designed in IBM 180nm CMOS process with a supply voltage of 1.8V.

CRISP is a data acquisition and image reconstruction technique that offers theoretical increases in signal-to-noise ratio (SNR) and dynamic range over traditional methods in magnetic resonance imaging (MRI). The incoming broadband MRI signal is de-multiplexed into multiple narrow frequency bands using analog filters. Signal from each narrowband channel is then individually captured and digitized. The original signal is recovered by recombining all the channels via weighted addition, where the weights correspond to the frequency responses of each narrowband filter. With ideal bandpasses and bandwidth dependent noise after filtering, SNR increase is proportional to sqrt(N), where N is the number of bandpasses. In addition to SNR improvement, free induction decay (FID) echoes in CRISP experience a slower decay rate. In situations where resolution is limited by digitization noise, CRISP is able to capture data further out into the higher frequency regions of k-space, which leads to a relative increase in resolution. The conversion from one broadband MR signal into multiple narrowband channels is realized using a comb or bank of active analog bandpass filters. A custom CRISP RF receiver chain is implemented to downconvert and demodulate the raw MR signal prior to narrowband filtering, and to digitize the signals from each filter channel simultaneously. Results are presented demonstrating that the CRISP receiver chain can acquire 2D MR images (without narrowband filters) with SNR similar to SNR of images obtained with a clinical system. Acquiring 2D CRISP images (with narrowband filters) was not possible due to the lack of phase lock between rows in k-space. RMS noise of narrowband, broadband and unfiltered 1D echoes are compared.

CRISP is a data acquisition and image reconstruction technique that offers theoretical increases in signal-to-noise ratio (SNR) and dynamic range over traditional methods in magnetic resonance imaging (MRI). The incoming broadband MRI signal is de-multiplexed into multiple narrow frequency bands using analog filters. Signal from each narrowband channel is then individually captured and digitized. The original signal is recovered by recombining all the channels via weighted addition, where the weights correspond to the frequency responses of each narrowband filter. With ideal bandpasses and bandwidth dependent noise after filtering, SNR increase is proportional to sqrt(N), where N is the number of bandpasses. In addition to SNR improvement, free induction decay (FID) echoes in CRISP experience a slower decay rate. In situations where resolution is limited by digitization noise, CRISP is able to capture data further out into the higher frequency regions of k-space, which leads to a relative increase in resolution. The conversion from one broadband MR signal into multiple narrowband channels is realized using a comb or bank of active analog bandpass filters. A custom CRISP RF receiver chain is implemented to downconvert and demodulate the raw MR signal prior to narrowband filtering, and to digitize the signals from each filter channel simultaneously. Results are presented demonstrating that the CRISP receiver chain can acquire 2D MR images (without narrowband filters) with SNR similar to SNR of images obtained with a clinical system. Acquiring 2D CRISP images (with narrowband filters) was not possible due to the lack of phase lock between rows in k-space. RMS noise of narrowband, broadband and unfiltered 1D echoes are compared.

No description available.

Third generation mobile communication systems promise a greater data rate and new services to the mobile subscribers. 3G systems support up to 2 Mbps of data rate to a fixed subscriber and 144 Kbps of data rate to a fully mobile subscriber. Code Division Multiple Access (CDMA) is the air interface access scheme widely used in all the 3G communication systems. This access scheme has many inherent advantages m terms of noise immunity, security, coherent combining of multi path signals etc. But all these advantages come at the expense of higher complexity of the receivers. The receivers form the major portion of the processing involved in a base station. The heart of any CDMA receiver is the RAKE. The RAKE receiver separates the different multi-paths received by the antenna by using the properties of the Pseudo Random sequences. The phase and strength of each of these path signals is measured and are used by the coherent combiner, which de-rotates all the signals to a single reference and coherently combines them In general the Base station receivers make use of the top three multi-path signals ranked in terms of their signal energy Hence four RAKE fingers, each catering to single multi-path are needed for receiving a single code channel (3 for coherent combining and one for scanning). One such channel receiver requires a processing power of 860 MIPS (Mega Instructions Per Second). Some of the CDMA standards support up to 90 code channels at the same time. This means that the total processing power required at the base station is about 80 GIPS. This much of processing power will require large number of high end DSPs, which will be a very costly solution. In the current base station architectures these blocks are implemented using ASICs, which are specific to a particular standard and also the algorithms used for the different operations are fixed at the design time itself. This solution is not flexible and is not amenable for SDR (Software defined Radio) architectures for the Base stations. This thesis proposes a Co-Processor solution, which can be attached to a generic DSP or any other processor. The processor can control the Co-Processor by programming its parameter registers using memory mapped register accesses. This co-processor implements only those blocks, which are compute intensive. This co-processor performs all chip-rate processing functions involved m a RAKE receiver. All the symbol-rate functions are implemented through software in the processor. This provides more choices m selecting the algorithms for timing recovery and scanning. The algorithms can be changed through software even after the base station is installed in the field. All the inputs and outputs of the Co-Processor are passed through dual port RAMs with independent read and write clocks. This allows the Co-Processor and the processor to be running on two independent clocks. This memory scheme also increases the throughput as the reads and writes to these memories can happen simultaneously. This thesis introduces a concept of incorporating programmable PN/Gold code generators as part of the Co-Processor, which significantly reduces the amount of memory required to store the Scrambling and Spreading codes. The polynomial lengths as well as the polynomials of the code generator are programmable. The input signal memory has a bus width equal to 4 times the bus width of the IQ signal bus width (4 * 24 = 96 bits) towards the Co-Processor to meet the huge data bandwidth requirement. This memory is arranged as word interleaved memory banks. This can supply one word per memory bank on each clock cycle as long as the accessed words fall in different memory banks. The number of banks is chosen as more than twice that of the number of Correlators/ Rake fingers. This gives more flexibility in choosing the address offsets to different Correlator inputs. This flexibility allows one to use different timing recovery schemes since the number of allowable address offsets for different Correlators is more. The overall complexity of the solution is comparatively less with respect to the generic DSP based solution and much easier to modify for a different standard, when compared to the rigid ASIC based solution. The proposed solution is significantly different from the conventional way of designing the Base station with fixed ASICs and it clearly outweighs the solutions based on conventional approach in terms of flexibility, design complexity, design time and cost.

La lithosphère continentale est physiquement et chimiquement segmentée. La cartographie des isotopes radiogéniques de roches plutoniques acides, représentatives de la croûte continentale, et de laves basiques, représentatives du manteau, possède des similarités avec la cartographie sismique de la lithosphère sous-jacente. Ces similitudes permettent d’interpréter les observations sismiques en étudiant leurs caractéristiques chimiques et leur âge. Les isotopes du plomb permettent de dater et d’identifier l’empilement de segments crustaux qui forment la croûte. L’écart des âges modèles du plomb avec d’autres systèmes identifie le recyclage crustal et le réchauffement de la croûte au dessus de la température du système plomb-plomb. Le système plomb-plomb donne également accès au sous-étudié rapport Th/U qui contraint la profondeur de la source des roches continentales. Certains échantillons de l’ouest U.S.A. proviennent de la croute inférieure, et se sont formés par l’extension crustale ou par un flux de matériel au sein de la croûte. Les isotopes du néodyme et de l’hafnium marquent la fusion du manteau lithosphérique enrichis sous le Colorado Plateau, une région où est observée le détachement du manteau lithosphérique sub-continental. Ce manteau fond par décompression adiabatique, par extension localisée ou remontée asthénosphérique engendrée par la convection locale. Au final, l’association des systèmes isotopiques du plomb, du néodyme, et de l’hafnium avec la sismologie est une approche puissante pour étudier la formation et la déformation de la lithosphère continentale. / Continental lithosphere is physically and chemically segmented. The mapping at a continent size scale of radiogenic isotopes from plutonic acid rocks, sampling the continental crust, and from mafic lavas, sampling the mantle, has similarities with the seismic mapping of the underlying lithosphere. These similarities allow to interpret the seismic observations by studying their chemical characteristics and age. Lead isotopes are used to date and identify the stacking of crustal segments that form the crust. The deviation of Lead model ages with other system is used to identify crustal recycling and the heating of the crust above the Lead-Lead system closing temperature. The Lead-Lead system also give access to the under-studied Th/U ratio that constrains the depth of the continental rock sources. Somes samples from the Western U.S. are coming from the lower crust, formed by crustal extension or crustal flowing within the crust. Neodymium and Hafnium isotopes identify the fusion of an enriched lithospheric mantle under the Colorado Plateau, a place where lithospheric delamination has been observed. This mantle melts by adiabatic decompression due to localized expansion or asthenospheric upwelling caused by secondary convection. At the end, the merging of Lead, Neodymium, and Hafnium isotopic systems with seismology is a powerful tool to study the formation and deformation of the continental lithosphere.

The aim of this thesis is to study the methods of a free space optical link design and its application in the communication technologies. The thesis describes possible intrusive influences on the transmitted optical signal, which are the signal noise, atmospheric attenuation and atmospheric turbulences. The thesis is particulary focused on the influence of the atmospheric turbulences and atmospheric attenuation on the optical beam.