A fast measurement technique based on the modulation phase-shift technique is developed to measure the wavelength-dependent magnitude and phase responses of optical devices. The measured phase response is in the form of group delay, which is used to determine the chromatic dispersion in the device under test by taking the derivative of the group delay with respect to optical wavelength. The measurement setup allows both step-tunable and sweeping laser sources. A modulation frequency of up to 2.7 GHz is accommodated. An alternate method for the phase measurement that overcomes non-linearities in the measurement setup is also presented. The speed of the measurement setup is limited by the sweeping speed of the laser source, which for the Agilent 81682A is 40 nm/sec. The magnitude accuracy is determined by taking a comparison to the commercially available Micron Finisar measurement system, where an error of 0.125 dB is noted. The phase accuracy of the measurement setup is tested by taking the Hilbert transform of the measured magnitude response of an Acetylene gas cell and comparing it to the integral of the measured group delay. The average deviation between the two methods is 0.1 radians. An Acetylene gas cell, fiber Bragg grating, and chirped Bragg grating are tested with the measurement setup and the Agilent 8168The characterization of the setup leads to the conclusion that the measurement setup developed in this paper is fast and accurate. The speed of the technique is on the order of microseconds for a single measurement and excels beyond the speed of the standard modulation phase-shift technique, which includes measurement times on the order of minutes. The accuracy of the technique is within 0.125 dB for magnitude measurements and 0.1 radians for phase measurements when compared to commercially available measurement systems.2A laser source at 40 nm/sec and the measurement plots are presented.

Owing to the need of high-directivity radiation in fix-point communication, this thesis designs the metamaterial with 4-fold rotational symmetric unitcells. Using their nearing-zero refractive index along two polarizations, we can get gain-enhanced antenna radomes and place them above dual- and circular-polarized antenna to verify our idea. It is known that the group delay variation in a communication system causes the degradation of symbol error rate, and positive group delay (GD) causes delay in signal propagation. Therefore, this research studies the negative group delay (NGD) behavior of metamaterial. Through analyzing the GD of metamaterial equivalent circuit caused by poles and zeros, we design a novel NGD bandpass circuit. Furthermore, this thesis develops graphic method for group delay investigatiion and study the relationship between NGD, loss and gain in order to simplify the design of GD compensation circuit.

This thesis presents the results for the temperature variation of the Differential Group Delay (DGD) measurements of a Dispersion Compensation Module (DCM) and interprets the results with a theoretical DGD model based on glass viscoelastic properties and estimated values of some of glass parameters. The results of our analysis demonstrate the existence of long birefringence relaxation times on the order of many hours in response to temperature changes. These results could be of significance in interpreting the behavior of optical fiber systems.

An essential step to achieving human-machine speech communication with the naturalness of communication between humans is developing a machine that is capable of recognising emotions based on speech. This thesis presents research addressing this problem, by making use of acoustic and prosodic information. At a feature level, novel group delay and weighted frequency features are proposed. The group delay features are shown to emphasise information pertaining to formant bandwidths and are shown to be indicative of emotions. The weighted frequency feature, based on the recently introduced empirical mode decomposition, is proposed as a compact representation of the spectral energy distribution and is shown to outperform other estimates of energy distribution. Feature level comparisons suggest that detailed spectral measures are very indicative of emotions while exhibiting greater speaker specificity. Moreover, it is shown that all features are characteristic of the speaker and require some of sort of normalisation prior to use in a multi-speaker situation. A novel technique for normalising speaker-specific variability in features is proposed, which leads to significant improvements in the performances of systems trained and tested on data from different speakers. This technique is also used to investigate the amount of speaker-specific variability in different features. A preliminary study of phonetic variability suggests that phoneme specific traits are not modelled by the emotion models and that speaker variability is a more significant problem in the investigated setup. Finally, a novel approach to emotion modelling that takes into account temporal variations of speech parameters is analysed. An explicit model of the glottal spectrum is incorporated into the framework of the traditional source-filter model, and the parameters of this combined model are used to characterise speech signals. An automatic emotion recognition system that takes into account the shape of the contours of these parameters as they vary with time is shown to outperform a system that models only the parameter distributions. The novel approach is also empirically shown to be on par with human emotion classification performance.

In previous studies it was determined that the fiber diameter distribution in a peripheral nerve could be estimated by a simulation technique known as group delay. These results could be further improved using a combinatorial optimization algorithm called simulated annealing. This paper explores the structure and behavior of simulated annealing for the application of optimizing the group delay estimated fiber diameter distribution. Specifically, a set of parameters known as the cooling schedule is investigated to determine its effectiveness in the optimization process. Simulated annealing is a technique for finding the global minimum (or maximum) of a cost function which may have many local minima. The set of parameters which comprise the cooling schedule dictate the rate at which simulated annealing reaches its final solution. Converging too quickly can result in sub-optimal solutions while taking too long to determine a solution can result in an unnecessarily large computational effort that would be impractical in a real-world setting. The goal of this study is to minimize the computational effort of simulated annealing without sacrificing its effectiveness at minimizing the cost function. The cost function for this application is an error value computed as the difference in the maximum compound evoked potentials between an empirically-determined template distribution of fiber diameters and an optimized set of fiber diameters. The resulting information will be useful when developing the group delay estimation and subsequent simulated annealing optimization in an experimental laboratory setting.

Peripheral neuropathy refers to diseases of or injuries to the peripheral nerves in the human body. The damage can interfere with the vital connection between the central nervous system and other parts of the body, and can significantly reduce the quality of life of those affected. In the US, approximately between 15 and 20 million people over the age of 40 have some forms of peripheral neuropathy. The diagnosis of peripheral neuropathy often requires an invasive operation such as a biopsy because different forms of peripheral neuropathy can affect different types of nerve fibers. There are non-invasive methods available to diagnose peripheral neuropathy such as the nerve conduction velocity test (NCV). Although the NCV is useful to test the viability of an entire nerve trunk, it does not provide adequate information about the individual functioning nerve fibers in the nerve trunk to differentiate between the different forms of peripheral neuropathy. A novel technique was proposed to estimate the individual nerve fiber diameters using group delay and simulated annealing optimization. However, this technique assumed that the fiber depth is always constant at 1 mm and the fiber activation due to a stimulus is depth independent. This study aims to incorporate the effect of fiber depth into the fiber diameter estimation technique and to make the simulation more realistic, as well as to move a step closer to making this technique a viable diagnostic tool. From the simulation data, this study found that changing the assumption of the fiber depth significantly impacts the accuracy of the fiber diameter estimation. The results suggest that the accuracy of the fiber diameter estimation is dependent on whether the type of activation function is depth dependent or not, and whether the template fiber diameter distribution contains mostly large fibers or both small and large fibers, but not dependent on whether the fiber depth is constant or variable.

Loudspeakers are used professionally and for leisure as a device which presents audio information to a listener. Loudspeakers “color” this information in different ways because of different properties, which they inherit from the decisions made in the design process. This study investigated the audibility of phase distortion in loudspeaker systems in ecologically valid environments using different types of program material and levels of group-delay. 13 subjects participated in a listening test, each performing 48 trials across various conditions. Results revealed significant differences in the ability to differentiate between reference and impaired signals based on program material and impairment level. Notably, participants demonstrated better discrimination for simple transient sounds compared to a mixed music recording. These results suggest that phase distortion may be less audible in mixed music reproduction than in click-like sounds. However, findings indicate a lower audible threshold for phase distortion compared to existing literature for click-like stimuli. Overall, while phase distortion may not always be audible, consideration for it can be relevant for achieving high audio quality in loudspeaker systems. These findings hopefully contribute to the understanding of phase distortion's perceptual effects and its implications for audio engineering and consumer electronics design.

The code observable of global navigation satellite systems (GNSS) is influenced by group delay variations (GDV) of transmitter and receiver antennas. For the Global Positioning System (GPS), the variations can sum up to 1 m in the ionosphere-free linear combination and thus can significantly affect precise code applications. The contribution of the GPS transmitters can amount to 0.8 m peak-to-peak over the entire nadir angle range. To verify the assumption of their time-invariance, we determined daily individual satellite GDV for GPS transmitter antennas over a period of more than two years. Dual-frequency observations of globally distributed reference stations and their multipath combination form the basis for our analysis. The resulting GPS GDV are stable on the level of a few centimeters for C1, P2, and for the ionosphere-free linear combination. Our study reveals that the inconsistencies of the GDV of space vehicle number (SVN) 55 with respect to earlier studies are not caused by temporal instabilities, but are rather related to receiver properties.

The code observable of global navigation satellite systems (GNSS) is influenced by group delay variations (GDV) of transmitter and receiver antennas. For the Global Positioning System (GPS), the variations can sum up to 1 m in the ionosphere-free linear combination and thus can significantly affect precise code applications. The contribution of the GPS transmitters can amount to 0.8 m peak-to-peak over the entire nadir angle range. To verify the assumption of their time-invariance, we determined daily individual satellite GDV for GPS transmitter antennas over a period of more than two years. Dual-frequency observations of globally distributed reference stations and their multipath combination form the basis for our analysis. The resulting GPS GDV are stable on the level of a few centimeters for C1, P2, and for the ionosphere-free linear combination. Our study reveals that the inconsistencies of the GDV of space vehicle number (SVN) 55 with respect to earlier studies are not caused by temporal instabilities, but are rather related to receiver properties.

La technologie ultra large bande impulsionnelle améliore la précision des systèmes de localisation en intérieur, en limitant les perturbations potentielles liées aux multi-trajets. Une nouvelle norme, destinée aux situations d’urgence, relève le niveau d’émission de puissance de 20 dB, afin de faciliter la localisation au travers d’obstacles épais et l’intervention des secours. Cette thèse s’est attelée à la conception d’un amplificateur conforme à cette norme. Après un état de l’art des amplificateurs de puissance ultra large bande existants, plusieurs circuits sont conçus : une cellule de puissance pour atteindre les niveaux de puissance requis en sortie, et une cellule pré amplificatrice qui fournit un apport de gain. Enfin, un système d’amplification de puissance à polarisation contrôlée exploitant la nature impulsionnelle du signal est proposé. La limitation de l’activation de l’amplificateur à la seule manifestation d’une impulsion permet de réduire drastiquement l’impact énergétique du PA sur un système de localisation. / The use of impulse radio (IR) ultra-wideband (UWB) technology for indoor localization systems both improves signal accuracy and reduces disturbances from multipath. A new standard for emergency situations requires the design of a higher output power UWB power amplifier (PA) as the usual maximum output power has been raised by 20 dB in order to allow the signal to pass through thick obstacles, thus helping rescue operations. First, a UWB PA state of the art is presented, and the design of both a power cell and a driver cell are detailed, to achieve the required output power level and additional gain, respectively. Finally, a bias controlled amplification system is described, taking advantage of the IR profile of the UWB signal. The PA is activated only for pulse occurrences, reducing drastically its power consumption.