In this thesis, we study the performance of an antenna switching (AS) system in comparison to an Alamouti coded system. We analyze the outage probabilities and propose minimum mean-squared error based iterative equalizers for both systems. We see from the outage probability analysis of both systems that the AS system may achieve the same diversity order of the Alamouti coded scheme contingent on the transmission rate and constellation size. In the proposed receiver, MMSE equalization and channel decoding are jointly carried out in an iterative fashion. We use both hard and soft decision channel decoders in our simulations. It is observed that the Alamouti based scheme performs better when the channel state information is perfect. The Alamouti scheme also performs better than the AS scheme when the channel state information is imperfect in hard decision channel decoder case and a random interleaver is used. On the other hand, if a random interleaver is not used, AS scheme performs remarkably better than the Alamouti scheme in hard decision channel decoder case. In a soft decision channel decoder case, when the channel state information is imperfect, the AS scheme performs approximately a 2 dB better than the Alamouti scheme. Moreover, there is approximately a 3 dB performance gain if a soft decision channel decoder is used instead of hard decision.

In practice, there exist many error sources which distort the antenna array pattern. For example, elements of antenna arrays influence each other (known as mutual coupling), mismatches in cables and element positions affects the antenna radiation pattern and also unequal gain and phase characteristics of RF receiver distorts the received signal. These effects generally degrade the array performance. They cause an increase in sidelobe levels with an accompanying decrease in gain. Also, these errors limit the performance of direction finding (DF) algorithms. So, in order to have low sidelobe level, good performance in direction finding and beamforming, calibration is necessary. In the literature, there exist many algorithms proposed for the calibration of errors. Calibration method used in this thesis assumes that there is a linear transformation between ideal signal and measurements. Calibration matrix is formed by using measurements. In this work, we look for the adequate number of measurements for successful calibration. Performance of calibration method may depend on the angle interval from which measurements are taken. So, the width of the data collection angle interval is also studied. Moreover, in real life, measurements can be collected from equally or randomly spaced angles. Does it affect the performance of calibration? The answer of this question is also inspected in this thesis. Additionally, the performance of algorithm under noise is studied. Performance evaluation is done for both elevation and azimuth sectors. Simulations are carried out on MATLABTM and Ansoft HFSS software package.

Energy or DFT detector using a fixed window size is very efficient when signal start time and duration is matched with that of the window&#039 / s. However, in the case of unknown signal duration, the performance of this detector decreases. For this scenario, a detector system composed of multiple windows may be preferred. Window sizes of such a system will also be fixed beforehand but they will be different from each other. Therefore, one of the windows will better match the signal duration, giving better detection results. In this study, multiple window detectors are analyzed. Their false alarm and detection probability relations are investigated. Some exact and approximate values are derived for these probabilities. A rule of thumb for the choice of window lengths is suggested for the case of fixed number of windows. Detectors with overlapping window structure are considered for the signals with unknown delay. Simulation results are added for these types of detectors.

Conventional methods of CFAR detection always use windowing, in the sense that some number of cells are investigated and the target present/absent decision is made according to the composition of the cells in that window. The most commonly used versions of CFAR detection algorithms are cell averaging CFAR, smallest of cell averaging CFAR, greatest of cell averaging CFAR and order-statistics CFAR. These methods all use windowing to set the decision threshold. In this thesis, rather than using windowed CFAR algorithms, a new method of estimating the background threshold is presented, analyzed and simulated. This new method is called the Switching IIR CFAR algorithm and uses two IIR filters to accurately estimate the background threshold. Then, using a comparison procedure, one of the filters is selected as the current threshold estimate and used. The results are seen to be satisfactory and comparable to conventional CFAR methods. The basic advantages of using the SIIR CFAR method are computational simplicity, small memory requirement and acceptable performance under clutter edges and multiple targets.

A complex exponential waveform embedded in white noise can be optimally detected by matched filtering which is equivalent to Discrete Fourier Transform (DFT). However, if the input includes multiple complex exponentials, the DFT processing is not optimal. The frequency spectrum of the complex exponential signal with finite observation interval is not impulse. The spectrum includes side-lobes called spectral leakage.Because of the strong side-lobes, weak components can be masked, or side-lobes can be interpreted as independent complex exponentials causing false alarms. The conventional approach is to suppress side-lobes by using an amplitude weighting function, called a window function. However, windows reduce the signal to noise ratio at the output and also widens the main lobe in the spectrum resulting in a loss of frequency resolution. In this thesis, the problem of detection of a complex exponential signal under a secondary complex exponential interference is investigated. Alternative windowing techniques such as spatially variant apodization (SVA), dual apodization (DA) are studied in the context of detection of weak sinusoids under strong sinusoidal interference. The detection performance of SVA and DA is compared with the conventional methods and the optimal detector.

In this thesis a single stage detector logarithmic video amplifier is designed with a dynamic range of 40dB in 2-6GHz frequency band. Since the detector logarithmic video amplifier (DLVA) is used to convert the power of the RF signals to video voltages in logarithmic scale, it can be regarded as a logarithmic converter instead of logarithmic amplifier. The design is composed of two main parts: The Schottky diode detector rectifies the incoming RF signal and produces a video voltage and the logarithmic amplifier transforms the scale of the video voltage from linear scale to logarithmic scale in order to observe the RF signals with a wide amplitude range. The approximation of the logarithmic function is obtained by the summation of the output currents of the differential amplifiers operating as logarithmic stages. Offset voltage of the DLVA is minimized in order to obtain maximum sensitivity / this makes the detection of RF signals with low power possible. The study is composed of mainly three parts: First, brief information about logarithmic amplification techniques is given and the circuit architecture is developed for logarithmic amplification and video detection, second these circuits are simulated and finally the design is implemented and tested.

<p>BACKGROUND: A telephone nurse is a nurse that during most of its working time is engaged in healthcare advice via the telephone. The advent of the telephone healthcare advice has probably meant that individuals, who initially wouldn’t have sought help, if they needed to meet healthcare providers face to face, now actually have the confidence to turn to healthcare. For telephone healthcare advice is professional care to identify, assess and advise on individuals’ reactions to actual or potential health problems. AIM: The aim of this literature review was to illuminate how the nurses´ assessment was affected during giving telephone advice. METHOD: This literature review has a qualitative approach and was conducted through twelve analyzed articles which were from the nurses’ point of view. FINDINGS: Two categories emerged from analyzing the articles. These were ethical dilemmas and assessment tools. The first category deals with the ethical dilemmas the telenurses’ are facing while giving advice via the telephone. The second category present which tools the telephone nurses have available or needs for assessment. DISCUSSION: It seems like the telenurses’ are drawn between the limited accesses to healthcare, the care seekers’ agenda and the demands of how them as nurses’ are expected to act.  CONCLUSION:   Possessing coping strategies related to stress and responsibility are valuable factors for the telenurses’ assessment process. Future research is felt to be needed on the subject of how the nurse deals with stress and the feeling of responsibility.</p><p> </p> / <p>BAKGRUND: En telefonsjuksköterska är en sjuksköterska som till största del under sitt arbete ägnar sig åt hälso- och sjukvårdsrådgivning via telefon. Framväxten av telefonrådgivning har troligtvis gjort att individer som inte skulle ha sökt vård om de behövt möta vårdgivaren ansikte mot ansikte, nu faktiskt vågar vända sig till sjukvården. När det gäller telefonrådgivning är professionell omvårdnad att identifiera, bedöma och ge råd kring individens aktuella eller potentiella hälsoproblem. SYFTE: Syftet med studien var att belysa vad som påverkar sjuksköterskors bedömning vid telefonrådgivning. METOD: Denna litteraturöversikt har en kvalitativ ansats och bygger på tolv analyserade artiklar som har ett sjuksköterskeperspektiv. RESULTAT: Två kategorier framkom från analysen. Dessa var etiska dilemman och redskap för bedömning. Den första kategorin tar upp de etiska dilemman som telefonsjuksköterskor möter under telefonrådgivning. Den andra kategorin presenterar vilka redskap telefonsjuksköterskor har att tillgå eller behöver för sin bedömning. DISKUSSION: Det verkar som telefonsjuksköterskor dras mellan den limiterade tillgängligheten till hälso- och sjukvård, de vårdsökandes agenda och kraven på hur de i sin sjuksköterskeprofession förväntas agera. KONKLUSION: Stresshantering och känslan av ansvar anses som viktiga faktorer som kan påverka sjuksköterskors bedömning. Framtida forskning önskas om hur telefonsjuksköterskor kan hantera dessa faktorer.</p>

Thesis (M. Phil.)--University of Hong Kong, 1983.

Thesis (M.B.A.)--University of Hong Kong, 1981.

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 189-194). Also available on the Internet.