ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, Nevada / Modern telemetry systems using state of the art field programmable gate arrays (FPGAs) and signal processing components require lower voltage supplies to support various CMOS core geometries while still needing multiple higher voltage rails to support legacy interfaces. Addressing these power supply requirements efficiently requires switching power supply topologies that if left unchecked can generate high input surge currents and high levels of detrimental noise for both the sensitive analog signal processing circuitry and the power supply input source. This paper focuses on the design considerations and tradeoffs associated with implementing an efficient telemetry encoder power supply while mitigating the resulting noise effects typically associated with switching power supplies. This noise can negatively affect the power supply input source and the linear signal processing circuitry within the telemetry encoder.

International Telemetering Conference Proceedings / October 28-31, 1985 / Riviera Hotel, Las Vegas, Nevada / A novel source of noise is identified and described in this study. If a continuous recording medium is less than perfectly uniform, a given quantity may be recorded differently at different locations in the medium. Inadvertent “encoding” occurs, embedding noise in the signal. Symmetrical sideband noise power results from amplitude and phase modulation of the signal stream by the nonuniform recording medium. “Write noise”, so-called because writing is required, is correlated in amplitude with signal amplitude, and its mean frequency is the signal frequency. It is the dominant noise source for the current generation of recorders and tapes; its power spectrum is almost the same as the power spectrum of the signal. The ratio of standard deviation to mean value of the signal envelope when recording cw signals is an absolute measure of tape quality independent of record level, tape speed, and track width, and establishes an available signal-to-noise ratio which cannot be exceeded. It is assumed that the recorder output has a normal amplitude distribution about its mean value. Theory is confirmed by experiment, within experimental error, for cw and digital recording.

Anthropogenic noise in the sea is now classed as a pollutant alongside chemical pollution and marine litter in accordance with the Marine Strategy Framework Directive. Noise from shipping is a major contributor to the ambient noise levels in the ocean, particularly at low (<300Hz) frequencies. The properties of sound propagation in shallow waters are highly influenced by the marine physical environment. Ocean modelling plays an important role in underwater noise studies since it can provide high resolution water column parameters over large geographic areas. This study investigates the noise patterns and their temporal variations in the Celtic Sea by using a coupled ocean model (POLCOMS) and an acoustic model (HARCAM). A method to predict noise exposure experienced by marine animals is then developed, following an application for diving seals. The ocean model is applied in the Celtic Sea to provide high-resolution 3D hourly temperature and salinity fields for the acoustic model. The model is validated against in-situ and satellite observations, giving high skills to simulate the water column structures. Sensitivity studies of modelled results to different atmospheric forcing are carried out in order to improve the accuracy of the model. The results show that the modelled sea surface temperature, stratification and water column structures are highly sensitive to the choice of surface forcing, especially in the summer time. The increase in resolution of surface forcing does not necessarily lead to more accurate results. The tidally frontal position is, however, insensitive to the forcing. The variability of noise propagation is studied using the coupled model, demonstrating high dependence on oceanographic conditions, geographic location of sound source and its depth. In summer, when the source of sound is on the inshore side of the bottom front, the sound energy is mostly concentrated in the near-bottom layer. In winter, the sound from the same source is distributed more evenly in the vertical. When the source is on the seaward side of the front, the sound level from a shallow source is nearly uniform in the vertical and the transmission loss is significantly greater (~16dB at 40km distance) in summer than in winter. In contrast, sound energy from a deep source is trapped in the bottom cold water, leading to a much lower transmission loss (~20dB) in summer than in winter. Note that ~10dB fluctuation of sound energy is found during the deterioration of the thermocline in late autumn. Shallow sources (e.g. ships) are sensitive to the surface heat flux as it changes significantly the vertical temperature gradient, while tides play an important role in determining the TL variability of deeper sources (e.g. pile driving) since they cause adjustments of positions of subsurface fronts. The seasonal noise patterns radiated by a large cargo ship are modelled by relating the AIS ship track data and the coupled model, showing a clear influence of the seasonal thermocline and associated bottom fronts on shipping noise distribution. The noise propagates much further (tens of kilometres) in winter than in summer. The predicted shipping noise exposure perceived by grey seals shows strong step changes in the sound level during their descent/ascent through the water column. Since grey seals tend to be benthic foragers, a hypothesis that the step change in sound exposure may have negative impacts on their foraging behaviour is proposed for biological specialists.

International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, California / It is well known that the pulse telemetering system whose system equipment is simple is superior to the continuous one in ultilizing signal power. But in designing a pulse telemetering receiver the frequency shift problem is often encountered, the shift often greatly wider than the signal bandwidth is very unfavorable for improving receiver working sensitivity. Either to limit transmitter frequency stability strictly or to adapt AFC system in receiver for tracking carrier wave can solve the problem above, the AFC system method could improve the receiver’s performance, but the equipment is complicated. To what extent the receiver working sensitivity will be effected and how to judge the effection in case of adapting VF matched filter and RF being wideband in receiver are this paper’s emphasis. In this paper the power density spectrum distribution of the white noise which has passed through the non-linear system-the linear detector is analysed theoretically, and the improved working sensitivity of the receiver with video matched filter and its difference sensitivity value to that of the optimal receiver are derived. The tested working sensitivity data of two kind pulse receivers with different RF bands are given and the theoretical calculation results conform well with these data, thus it is proven that adapting video matched filter in pulse receiver is a effective approach for compensating the receiver working sensitivity dropping from RF bandwidth increase.

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

published_or_final_version / Urban Planning / Master / Master of Science in Urban Planning

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management