Recent government regulations for Enhanced 911 locating of wireless handsets require accuracy to within 50 and 300 meters. Two technologies under consideration are triangulation using existing wireless base stations and location using global positioning satellites (GPS). Satellite positioning is the leading candidate, however, reception of GPS signals within large buildings is difficult and considerable research is devoted to this topic. Conventional GPS receivers require line of sight to at least four satellites and, under outdoor conditions, the expected signal level is about -160 dBW. Within large buildings, detection is very difficult because there is high thermal noise and some satellite signals can be attenuated to less than -185 dBW while others can suffer little attenuation. In order to construct the pseudo-ranges necessary for position finding, the receiver must synchronize to the incoming codephase of each satellite and must operate with substantial Doppler frequency offset caused by satellite motion.<p> This thesis investigates the application of a parallel non-coherent spread spectrum synchronizer previously implemented as a very-large-scale integration (VLSI) circuit. The circuit processes one millisecond of incoming signal and uses a segmented matched filter (SMF) by which the segmentation provides some tolerance to Doppler shift. The thesis presents simulation results of averaging for tens of seconds. Through simulation, the SMF is compared with a transversal matched filter (TMF) under conditions of no Doppler shift; coherent and non-coherent integration are discussed. The simulation is conducted at 290 K (17°C) such that the Boltzmann noise is -204 dBW/Hz, with a GPS signal bandwidth of 2 MHz and signal level of -185 dBW, and the receiver input signal-to-noise ratio (SNR) is -44 dB.<p> The SMF is applied using differing segment lengths to high-sensitivity GPS data from indoor and urban simulated GPS data. The results demonstrate the SMFs ability to tolerate Doppler frequency offsets while allowing for long integration times to detect the weak GPS signals.

Recent government regulations for Enhanced 911 locating of wireless handsets require accuracy to within 50 and 300 meters. Two technologies under consideration are triangulation using existing wireless base stations and location using global positioning satellites (GPS). Satellite positioning is the leading candidate, however, reception of GPS signals within large buildings is difficult and considerable research is devoted to this topic. Conventional GPS receivers require line of sight to at least four satellites and, under outdoor conditions, the expected signal level is about -160 dBW. Within large buildings, detection is very difficult because there is high thermal noise and some satellite signals can be attenuated to less than -185 dBW while others can suffer little attenuation. In order to construct the pseudo-ranges necessary for position finding, the receiver must synchronize to the incoming codephase of each satellite and must operate with substantial Doppler frequency offset caused by satellite motion.<p> This thesis investigates the application of a parallel non-coherent spread spectrum synchronizer previously implemented as a very-large-scale integration (VLSI) circuit. The circuit processes one millisecond of incoming signal and uses a segmented matched filter (SMF) by which the segmentation provides some tolerance to Doppler shift. The thesis presents simulation results of averaging for tens of seconds. Through simulation, the SMF is compared with a transversal matched filter (TMF) under conditions of no Doppler shift; coherent and non-coherent integration are discussed. The simulation is conducted at 290 K (17°C) such that the Boltzmann noise is -204 dBW/Hz, with a GPS signal bandwidth of 2 MHz and signal level of -185 dBW, and the receiver input signal-to-noise ratio (SNR) is -44 dB.<p> The SMF is applied using differing segment lengths to high-sensitivity GPS data from indoor and urban simulated GPS data. The results demonstrate the SMFs ability to tolerate Doppler frequency offsets while allowing for long integration times to detect the weak GPS signals.

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.

Code-Division Multiple-Access (CDMA) is one of the leading digital wireless communication methods currently employed throughout the world. Third generation (3G) and future wireless CDMA systems are required to provide services to a large number of users where each user sends data burst only occasionally. The preferred approach is packet based CDMA so that many users share the same physical channel simultaneously. In CDMA, each user is assigned a pseudo-random (PN) code sequence. PN codephase synchronization between received signals and a locally generated replica by the receiver is one of the fundamental requirements for successful implementation of any CDMA technique. The customary approach is to start each CDMA packet with a synchronization preamble which consists of PN code without data modulation. Packets with preambles impose overheads for communications in CDMA systems especially for short packets such as mouse-clicks or ATM packets of a few hundred bits. Thus, it becomes desirable to perform PN codephase synchronization using the information-bearing signal without a preamble. This work uses a segmented matched filter (SMF) which is capable of acquiring PN codephase in the presence of data modulation. Hence the preamble can be eliminated, reducing the system overhead. Filter segmentation is also shown to increase the tolerance to Doppler shift and local carrier frequency offset. <p>Computer simulations in MATLAB® were carried out to determine various performance measures of the acquisition system. Substantial improvement in probability of correct codephase detection in the presence of multiple-access interference and data modulation is obtained by accumulating matched filter samples over several code cycles prior to making the codephase decision. Correct detection probabilities exceeding 99% are indicated from simulations with 25 co-users and 10 kHz carrier frequency offset or Doppler shift by accumulating five or more PN code cycles, using maximum selection detection criterion. Analysis and simulation also shows that cyclic accumulation can improve packet throughput by 50% and by as much as 100% under conditions of high offered traffic and Doppler shift for both fixed capacity and infinite capacity systems.

Code-Division Multiple-Access (CDMA) is one of the leading digital wireless communication methods currently employed throughout the world. Third generation (3G) and future wireless CDMA systems are required to provide services to a large number of users where each user sends data burst only occasionally. The preferred approach is packet based CDMA so that many users share the same physical channel simultaneously. In CDMA, each user is assigned a pseudo-random (PN) code sequence. PN codephase synchronization between received signals and a locally generated replica by the receiver is one of the fundamental requirements for successful implementation of any CDMA technique. The customary approach is to start each CDMA packet with a synchronization preamble which consists of PN code without data modulation. Packets with preambles impose overheads for communications in CDMA systems especially for short packets such as mouse-clicks or ATM packets of a few hundred bits. Thus, it becomes desirable to perform PN codephase synchronization using the information-bearing signal without a preamble. This work uses a segmented matched filter (SMF) which is capable of acquiring PN codephase in the presence of data modulation. Hence the preamble can be eliminated, reducing the system overhead. Filter segmentation is also shown to increase the tolerance to Doppler shift and local carrier frequency offset. <p>Computer simulations in MATLAB® were carried out to determine various performance measures of the acquisition system. Substantial improvement in probability of correct codephase detection in the presence of multiple-access interference and data modulation is obtained by accumulating matched filter samples over several code cycles prior to making the codephase decision. Correct detection probabilities exceeding 99% are indicated from simulations with 25 co-users and 10 kHz carrier frequency offset or Doppler shift by accumulating five or more PN code cycles, using maximum selection detection criterion. Analysis and simulation also shows that cyclic accumulation can improve packet throughput by 50% and by as much as 100% under conditions of high offered traffic and Doppler shift for both fixed capacity and infinite capacity systems.

This thesis performs a quantitative study, derived from the Neyman-Pearson framework, on the robustness of the matched filter detector corrupted by zero mean, independent and identically distributed white Gaussian noise. The variance of the noise is assumed to be imperfectly known, but some knowledge about a nominal value is presumed. We utilized slope as a unit to quantify the robustness for different signal strengths, nominals, and sample sizes. Following to this, a weighting method is applied to the slope range of interest, the so called tolerable range, as to analyze the likelihood of these extreme slopes to occur. A ratio of the first and last quarter section of the tolerable range have been taken in order to obtain the likelihood ratio for the low slopes to occur. We finalized our analysis by developing a method that quantifies confidence as a measure of robustness. Both weighted and non-weighted procedures were applied over the tolerable range, where the weighted procedure puts greater emphasis on values near the nominal. The quantitative analysis results show the detector to be non-robust and deliver poor performance for low signal-to-noise ratios. For moderate signal strengths, the detector performs rather well if the nominal and sample size are chosen wisely. The detector has great performance and robustness for high signal-to-noise ratios. This even remains true when only a few samples are taken or when the practitioner is uncertain about the nominal chosen.

Obtaining higher depth of imaging is an important goal in Optical Coherence Tomography (OCT) systems. One of the main factors that affect the depth of OCT imaging is the presence of noise. That’s why the study of noise statistics is an important problem. In the first part of this thesis we obtain an empirical estimate of the second order statistics of noise by using a sequence of Time domain (TD) OCT images. These estimates confirm the non-stationary nature of noise in TD-OCT. In the second part of the thesis these estimates are used to design a depth-dependent matched filter to maximize the Signal-to-Noise Ratio (SNR) and increase the Contrast-to-Noise Ratio (CNR) in TD-OCT. By applying our filter to TD-OCT images of both vascular rabbit tissue and a human tooth, both SNR and CNR were increased and a higher imaging depth was achieved.

Obtaining higher depth of imaging is an important goal in Optical Coherence Tomography (OCT) systems. One of the main factors that affect the depth of OCT imaging is the presence of noise. That’s why the study of noise statistics is an important problem. In the first part of this thesis we obtain an empirical estimate of the second order statistics of noise by using a sequence of Time domain (TD) OCT images. These estimates confirm the non-stationary nature of noise in TD-OCT. In the second part of the thesis these estimates are used to design a depth-dependent matched filter to maximize the Signal-to-Noise Ratio (SNR) and increase the Contrast-to-Noise Ratio (CNR) in TD-OCT. By applying our filter to TD-OCT images of both vascular rabbit tissue and a human tooth, both SNR and CNR were increased and a higher imaging depth was achieved.

Ultra-wideband (UWB) communications is expected to revolutionize high data-rate, short-distance wireless communications, providing data-rates in excess of 100 Mbps. However, the wireless channel distorts the transmitted signal by dispersing the signal energy over time. This degrades the output signal-to-noise ratio (SNR) of a correlation based matched-filter receiver, limiting the achievable data-rate and user capacity. Most wideband channel models do not account for all the identified dispersion mechanisms namely the frequency dispersion, the resonant dispersion and the multipath dispersion. The objective of this research is to model resonant dispersion based on the Singularity Expansion Method (SEM) and provide guidelines for UWB receiver design to meet the data capacity. The original contribution of this research is a novel pole dispersion channel model that includes resonant dispersion characterization. An empirical investigation supports our claim that a correlation type matched-filter receiver using a template signal based on the pole dispersion channel model overcomes distortion related losses. Various physical mechanisms responsible for dispersion in UWB communication systems are described in detail. The applicability of the proposed dispersive channel model is evaluated using the optimal matched filter (OMF) receiver. The SEM approach, which was originally proposed for target identification using short pulse radars, offers limited benefits of due to its susceptibility to noise. A combined fuzzy-statistical approach is proposed to improve the robustness of resonant dispersion channel modeling in presence of noise. A natural extension of this doctoral research is to improve buried landmine detection as well as breast tumor detection by applying statistical and fuzzy analysis to the backscatter response. Moreover, radar target identification using UWB short pulses stands to gain tremendously from this research. / Ph. D.

The thesis deals with the detection of the nerve fiber layer disruptions in retina scans. The introduction presents an overview of the human eye fysiology and analyses the input image data. The thesis continues with an investigation of two texture analysis methods. While the method of adapted filters does not produce very good results, the method of brightness assessment is shown to work satisfactorily. The final part of the thesis describes the implemented tool for the detection of the nerve fiber layer disruptions.