Beam-steerng digital num array paramétrico

Mestrado em Engenharia Electrónica e TelecomunicaçõesActualmente existem diversos m etodos que permitem a realiza c~ao de beamsteering num altifalante param etrico. No entanto, a maioria dos m etodos e incapaz de proporcionar uma elevada resolu c~ao angular usando um projecto de hardware e ciente. Mais ainda, poucos s~ao os sistemas que proporcionam um controlo do beam de pot^encia em tempo real. Neste documento, e proposta uma nova abordagem para colmatar estes problemas tirando partido da alta frequ^encia inerente a modula c~ao sigmadelta. Esta implementa c~ao leva a um projecto compacto que proporciona uma elevada resolu cao angular associada a uma solu c~ao de baixo custo e com baixo consumo de pot^encia devido ao uso de apenas uma DAC sigmadelta. O sistema implementado sobre FPGA alia a natural alta frequ^encia dum modulador sigma-delta ao uso dum unico shift-register para introduzir os atrasos necess arios a realiza c~ao de beam-steering. A escolha do atraso adequado e feita com o uso de multiplexers que encaminham os diversos sinais sigma-delta para as sa das do sistema desejadas.Several methods enable a steerable beam using an parametric loudspeaker. However, many of them are not able to use a high angular resolution with an e cient design. More, even the ability to change the beam steering in real time is neglected by several methods. In this document, we propose a new approach to the beam-steering problem using the intrinsic high frequency of a sigma-delta digital to analog converter conjugated with online con gurable digital delays obtained only through a programmable wide shift-register. This implementation leads to a real time beam-steering with a simple digital processing block that enables a high resolution angle. Additionally the use of a sigma-delta DAC provides a low-cost, highly integrated and energy e cient system using only a DAC. The implemented system takes advantage of the high frequency of the digital signal from the sigma-delta modulator allied with the use of a shiftregister to obtain the ne time delays necessary to do the beam-steering. The several outputs delays are chosen between the sigma-delta signals in the shift-register using a group of multiplexers

Electrophysiologic assessment of (central) auditory processing disorder in children with non-syndromic cleft lip and/or palate

Session 5aPP - Psychological and Physiological Acoustics: Auditory Function, Mechanisms, and Models (Poster Session)Cleft of the lip and/or palate is a common congenital craniofacial malformation worldwide, particularly non-syndromic cleft lip and/or palate (NSCL/P). Though middle ear deficits in this population have been universally noted in numerous studies, other auditory problems including inner ear deficits or cortical dysfunction are rarely reported. A higher prevalence of educational problems has been noted in children with NSCL/P compared to craniofacially normal children. These high level cognitive difficulties cannot be entirely attributed to peripheral hearing loss. Recently it has been suggested that children with NSCLP may be more prone to abnormalities in the auditory cortex. The aim of the present study was to investigate whether school age children with (NSCL/P) have a higher prevalence of indications of (central) auditory processing disorder [(C)APD] compared to normal age matched controls when assessed using auditory event-related potential (ERP) techniques. School children (6 to 15 years) with NSCL/P and normal controls with matched age and gender were recruited. Auditory ERP recordings included auditory brainstem response and late event-related potentials, including the P1-N1-P2 complex and P300 waveforms. Initial findings from the present study are presented and their implications for further research in this area —and clinical intervention—are outlined. © 2012 Acoustical Society of Americapublished_or_final_versio

Proceedings of the Second International Mobile Satellite Conference (IMSC 1990)

Presented here are the proceedings of the Second International Mobile Satellite Conference (IMSC), held June 17-20, 1990 in Ottawa, Canada. Topics covered include future mobile satellite communications concepts, aeronautical applications, modulation and coding, propagation and experimental systems, mobile terminal equipment, network architecture and control, regulatory and policy considerations, vehicle antennas, and speech compression

Abstracts on Radio Direction Finding (1899 - 1995)

The files on this record represent the various databases that originally composed the CD-ROM issue of "Abstracts on Radio Direction Finding" database, which is now part of the Dudley Knox Library's Abstracts and Selected Full Text Documents on Radio Direction Finding (1899 - 1995) Collection. (See Calhoun record https://calhoun.nps.edu/handle/10945/57364 for further information on this collection and the bibliography). Due to issues of technological obsolescence preventing current and future audiences from accessing the bibliography, DKL exported and converted into the three files on this record the various databases contained in the CD-ROM. The contents of these files are: 1) RDFA_CompleteBibliography_xls.zip [RDFA_CompleteBibliography.xls: Metadata for the complete bibliography, in Excel 97-2003 Workbook format; RDFA_Glossary.xls: Glossary of terms, in Excel 97-2003 Workbookformat; RDFA_Biographies.xls: Biographies of leading figures, in Excel 97-2003 Workbook format]; 2) RDFA_CompleteBibliography_csv.zip [RDFA_CompleteBibliography.TXT: Metadata for the complete bibliography, in CSV format; RDFA_Glossary.TXT: Glossary of terms, in CSV format; RDFA_Biographies.TXT: Biographies of leading figures, in CSV format]; 3) RDFA_CompleteBibliography.pdf: A human readable display of the bibliographic data, as a means of double-checking any possible deviations due to conversion

Modelocked vibronic lasers for the 700nm - 1000nm region

The work in this thesis is concerned with the characterisation and development of modelocked solid-state lasers covering the 700 - 1000 nm region. Results are presented for a passively modelocked LiF:F+2 colour-centre laser, however, most of the work has concentrated on the Ti: sapphire (Ti:Al2O3) laser. In chapter 2, the operation of a cw LiF: F+2 colour-centre laser is discussed. This laser was passively modelocked using the saturable absorber dye, DaQTeC and pulses as short as 170 fs were generated with average output powers of ~10 mW. Pulses as short as 127 fs were generated in a dispersion compensated, colliding-pulse modelocked geometry over a wavelength range of 925 - 950 nm. A nonlinear external cavity was added to the basic laser configuration in an attempt to extend the modelocked tuning range and the saturable absorber dye lifetime. The technique of coupled-cavity modelocking was applied to a Ti:Al2O3 laser and enabled pulses as short as 1.3 ps to be generated. These pulses were frequency chirped and could be directly compressed to 290 fs outside the laser. By using the technique of intracavity dispersion compensation in both the main and coupled cavities, pulses as short as 90 fs were generated, having average powers of ~200 mW and peak powers of more than 20 kW. The simpler technique of self-modelocking is described in chapter 5 and allowed the generation of pulses as short as 60 fs from a dispersion compensated cavity configuration. Average output powers of ~600 mW were measured, which corresponded to peak powers of 110 kW. This laser had a modelocked tuning range which spanned the 750 - 950 nm region. Using fibre/prism pulse compression techniques pulses as short as 45 fs were produced. In chapter 6, the measurement and suppression of phase noise on the self-modelocked Ti:Al2O3 laser are discussed. The technique for noise reduction was also applied to two similar self-modelocked lasers in an attempt to synchronise the two laser pulse sequences

Databook for human factors engineers. Volume 2 - Common formulas, metrics, definitions

Human factors engineering manual including mathematical formulas, nomographs, conversion tables, units of measurement, and nomenclature