Energy harvesters collect and convert energy available in the environment into useful electrical power to satisfy the power requirements of autonomous systems. Vibration energy is a prevalent source of waste energy in industrial and built environments. Vibration-based energy harvesters, or vibration-based micro power generators (VBMPGs), utilize a transducer, a mechanical oscillator in this application, to capture kinetic energy from environmental vibrations and to convert it into electrical energy using electromagnetic, electrostatic, or piezoelectric transduction mechanisms. A key design feature of all VBMPGs, regardless of their transduction mechanism, is that they are optimally tuned to harvest vibration energy within a narrow frequency band in the neighborhood of the natural frequency of the oscillator. Outside this band, the output power is too low to be conditioned and utilized. This limitation is exacerbated by the fact that VBMPGs are also designed to have high quality factors to minimize energy dissipation, further narrowing the optimal operating frequency band. Vibrations in most environments, however, are random and wideband. As a result, VBMPGs can harvest energy only for a relatively limited period of time, which imposes excessive constraints on their usability. A new architecture for wideband VBMPGs is the main contribution of this thesis. The new design is general in the sense that it can be applied to any of the three transduction mechanisms listed above. The linear oscillator is replaced with a piecewise-linear oscillator as the energy-harvesting element of the VBMPG. The new architecture has been found to increase the bandwidth of the VBMPG during a frequency up-sweep, while maintaining the same bandwidth in a frequency downsweep. Experimental results show that using the new architecture results in a 313% increase in the width of the bandwidth compared to that produced by traditional architecture. Simulations show that under random-frequency excitations, the new architecture collects more energy than traditional architecture. In addition, the knowledge acquired has been used to build a wideband electromagnetic VBMPG using MicroElectroMechanical Systems, MEMS, technology. This research indicates that a variety of piecewise-linear oscillators, including impact oscillators, can be implemented on MPG structures that have been built using MEMS technology. When the scale of the MPGs is reduced, lower losses are likely during contact between the moving oscillators and the stopper, which will lead to an increase in bandwidth and hence in the amount of energy collected. Finally, a design procedure has been developed for optimizing such wideband MPGs. This research showed that wideband MPGs require two design optimization steps in addition to the traditional technique, which is used in all types of generators, of minimizing mechanical energy losses through structural design and material selection. The first step for both regular and wideband MPGs minimizes the MPG damping ratio by increasing the mass and stiffness of the MPG by a common factor until the effect of size causes the rate at which energy losses increase to accelerate beyond that common factor. The second step, which is specific to wideband MPGs, tailors the output power and bandwidth to fit the Probability Density Function, PDF, of environmental vibrations. A figure of merit FoM was devised to quantify the quality of this fit. Experimental results show that with this procedure, the bandwidth at half-power level increases to more than 600% of the original VBMPG bandwidth.

Recent days, antennas play an important role in wireless communication system. Microstrip patch antennas are well known to have positive features for cost-effective, low profile and broadband. This type of antenna can be used in wide range of applications such as in wireless communications, radar systems, and satellites. Inhibiting characteristics of single patch antenna with low gain and narrow band leads to the research area to have array configuration. Beam steering antennas are the ideal solution for various systems such as traffic control and collision avoidance radar systems. The goal of this work is to design and implement a dual-linear polarization stacked microstrip patch phased array antenna. Single stacked microstrip patch antenna fed by microstrip line was designed to have approximately 3 GHz bandwidth in X-band with another ground plane to form a stripline-fed. Stripline-fed design protects feed lines from any outside effects. The array configuration was adapted to design in order to accomplish beam scan angle of /- 30 degrees by /- 15 degrees. Binomial power distribution of 3x2 array structure was used in order to reduce grating lobes, and changing length of feed lines was implemented for phase shifting. Bowtie cross shape aperture and dual-offset microstrip feedline was used to feed radiating patches. For the feed network, T-split power divider was implemented and optimized to achieve low loss. The length of microstrip line was adjusted to meet desired phase shift that in wideband application, the length of the line had to be long enough to have similar wavelength response over broad frequency range. The antenna array was designed using standard equations and simulated by electromagnetic analysis software called Zealand's IE3D which is method-of-moments based simulator. The resulting measured impedance bandwidth and gain of both microstrip and stripline-fed single antenna are 43 percent and 5 to 10 dBi with low cross polarizations for all frequencies. The array antenna was measured to have 29 to 60 percent impedance bandwidths depending on the different types of beam scan angles. The gain of the array antenna is 8 to 13 dBi, and the beams are directed as required with /- 3 degrees beam scan angle tolerance. The array antenna had a small offset as compared with simulated results because of the fabrication process such as alignment, distorted feed lines while etching, and etc, but the bandwidths and array patterns were acceptable.

In this thesis, an estimation method adapted from MUSIC algorithm is presented for estimation of signal arrival time for impulse radio UWB systems. An accurate estimate of signal arrival time is considered essential in time-based wireless and indoor location systems. Since most wireless communications systems used for indoor position location may suffer from dense multipath situation, the accuracy of determining signal arrival time become an important issue for the time-based location systems. The fine resolution of UWB signals provides potentially accurate ranging for indoor location applications. However, the ambiguity caused by the unresolved first arrival path may still yield an error in determining the true signal arrival time. The presented method uses improved MUSIC techniques in time domains to estimate the shortest and the real signal arrival time for UWB radio link. For a two-multipath case, analysis and simulation results of multipath resolvability and the variance of estimation errors of signal arrival time are discussed.

The maximum capacity of an optical fiber transmission system more than doubled every year to match the fast-growing communication need. The technology break through in dry fiber fabrication opens the possibility for fiber bandwidth all the way from 1.3 £gm to 1.6 £gm. The fast increasing demand of communication capacity results in the emergence of wavelength division multiplexing (WDM) technology, which results in the need for wideband optical amplifier. Cr4+:YAG has a strong spontaneous emission that covers 1.3 £gm to 1.6 £gm. Besides, its absorption spectrum is between 0.9 £gm to 1.2 £gm, which matches with the pumping source in current erbium doped optical amplifier. Such a fiber is, therefore, eminently suitable for optical amplifier applications. We have successfully fused the double cladding Cr4+:YAG crystal fiber with single mode fiber by fusion splicer. The crystal fibers are grown by the laser-heated pedestal growth technique. The splicing parameters are optimized to achieve an insertion loss of 3.8 dB. Througth the splicing images, we can quantitatively analyze the splicing results caused by fine tuned parameters, and aimed at the evolution of the ASE, that is dissipated into inner cladding. The simulation program is revised with better fitting. We can find the reason why net gain is under 0 dB by simulation result, and find the way to improve. Numerical simulation indicates that the gain can reach 2 dB at 1 W pump, if the core diameter of the double cladding Cr4+:YAG crystal fiber is reduced to 10 £gm. In the future, we¡¦ll reduce the core diameter of Cr4+:YAG crystal double cladding fiber to less than 10 £gm, and enhance the Cr4+ ion concentration to lower the insertion loss after two-sided splicing, Hopefull, super-wideband optical amplifier can be realized.

Novel microwave transmitter and receiver circuits have been developed for implementing UWB (Ultra-Wideband) impulse radar imaging sensor operating in frequency band 0.2 to 4 GHz. with tunable operating frequency band. The fundamental system design parameters such as the required transmitting pulse power and the pulse duration were estimated for a presumed specific application, the pavement assessment. The designed transmitter is the tunable monocycle pulse generator with tuning capability for the output pulse duration from 450- to 1200- ps, and has relatively high transmitting pulse power from 200 to 400 mW. Tuning of the pulse duration was implemented by novel PIN diode switch configuration and decoupling circuit, and boosting of transmitting pulse power was made possible by using a high power pulse driving circuit and SRD coupling circuit. The synchronous sampling receiver system was designed by using the integrated sampling mixer and two reference clock oscillators placed in the transmitter and receiver respectively for timing control. A novel integrated CSH (Coupled-Slotline Hybrid)sampling mixer has been developed along with the design of the strobe pulse generator appropriate for the impulse radar system. The integrated sampling mixer has unprecedented conversion loss of 2.5 dB for the pulse signal, bandwidth 5.5 GHz, and dynamic range 50 dB. The introduced UWB LNA (Low Noise Amplifier) design operating up to 4 GHz should be useful for weak signal detection applications. The design of the UWB microstrip quasi-horn antenna was optimized for short pulse transmission with respect to the input return loss and the pulse stretching effect. For signal detection in the signal processing stage, the background subtraction technique and B-scan data format were used. A novel signal monitoring technique was introduced in the signal processing to compensate the frequency modulation effect of the reference clock. The test results for the complete system with respect to some sample multi-layer structures shows good receiving pulse waveform with low distortion, enough pulse penetration depth for 13” pavement sample structure, and minimum 1-in of range resolution.

Thesis (M.S.)--Tennessee Technological University, 2009. / Title from title page screen (viewed on Feb. 9, 2010). Bibliography: leaves 102-108.

There are a growing number of ultra-wideband applications, which involve the radiation or reception of electromagnetic signals over frequency bandwidths ranging from 1.3:1 to over 10:1. In the design of antennas for ultra-wideband systems, many design objectives must be considered, including impedance matching, radiation efficiency, radiation pattern stability, size, and possibly impulse response. Given the very wide bandwidths considered, it can be challenging to meet all objectives simultaneously, and optimization techniques are useful to achieve a reasonable compromise between objectives. In this dissertation, multi-objective Genetic Algorithm (GA) optimization is used to design ultra-wideband antennas for use in wireless communications and low frequency radio astronomy. GA optimization is first applied to the design of ultra-wide bandwidth planar monopole antennas, which exhibit a narrow-band frequency notch in order to mitigate interference with co-located radio systems. The GA optimizer uses a weighted sum cost function related to impedance matching and radiation patterns at frequencies within both the wide operating band and the narrow notch band to improve antenna performance. A two-dimensional matrix chromosome is used in the GA to represent a wide-range on planar element shapes. It is shown that the GA generates antenna designs which exhibit wideband performance equal to traditional band-notched designs, but have improved azimuth plane radiation pattern symmetry, which widens the effective notch bandwidth. Pareto GA optimization is then applied to the design of planar dipole antenna elements operating over a ground plane for use in a low frequency radio telescope array. The objectives considered include Galactic background or "sky noise reception level, and radiation patterns over the operating band of 20 to 80 MHz. It is demonstrated that the Pareto GA approach generates a set of designs, which exhibit a wide range of trade-offs between the two design objectives, and satisfy all applied geometrical constraints. Multiple GA executions are performed to determine how antenna performance trade-offs are affected by different geometrical constraint values, feed impedance values, radiating element shapes and orientations, and ground conditions. In a follow-up to the previous study, the effects of mutual coupling in a low frequency radio telescope array are considered. It is first shown that a simple receive-based definition of coupling between two antennas can be used to design antenna elements which exhibit reduced mutual coupling effects when operated in a large phased array. This result is utilized in order to perform Pareto GA optimization of wire frame bow-tie dipole elements in terms of mutual coupling, as well as sky noise response and radiation patterns over the 20 to 80 MHz band. The GA generates a set of designs that span a wide range of objective values. The results are analyzed to understand the trade-offs that may be made between the three objectives. / text

Σκοπός αυτής της διπλωματικής εργασίας είναι η μελέτη, σχεδίαση και εξομοίωση τυπωμένων υπερευρυζωνικών κεραιών, κατάλληλων για χρήση σε ασύρματα δίκτυα προσωπικού χώρου. Στο πρώτο κεφάλαιο, ορίζονται βασικές έννοιες της θεωρίας κεραιών που είναι απαραίτητες για την κατανόηση των κεφαλαίων που ακολουθούν. Επιπλέον, γίνεται μια μικρή αναφορά στο πρόγραμμα ADS Momentum που χρησιμοποιήσαμε κατά την εξομοίωση των κεραιών. Στο δεύτερο κεφάλαιο, παρουσιάζονται τα ιδιαίτερα χαρακτηριστικά, η ιστορική εξέλιξη, τα πλεονεκτήματα καθώς και οι σημαντικότερες εφαρμογές της υπερευρυζωνικής τεχνολογίας Στο τρίτο κεφάλαιο, περιγράφονται οι επιθυμητές ιδιότητες των υπερευρυζωνικών κεραιών, κάποιες τεχνικές επίτευξης προσαρμογής σε μεγαλύτερο εύρος συχνοτήτων και παράμετροι βέλτιστου σχεδιασμού των στοιχείων. Εν συνεχεία, γίνεται αναφορά σε όλες τις κατηγορίες υπερευρυζωνικών κεραιών και τέλος παρατίθενται παραδείγματα για κάθε μία από τις τρεις κατηγορίες τυπωμένων κεραιών που θα εξετάσουμε. Στο τέταρτο κεφάλαιο, μελετώνται οι μονοπολικές τυπωμένες υπερευρυζωνικές κεραίες. Για τον σκοπό αυτό σχεδιάστηκαν και εξομοιώθηκαν δύο μονοπολικές κεραίες κυκλικού δίσκου τροφοδοτούμενες, η πρώτη από μικροταινιακή γραμμή και η δεύτερη από ομοεπίπεδο κυματοδηγό. Στο πέμπτο κεφάλαιο, μελετώνται οι διπολικές τυπωμένες υπερευρυζωνικές κεραίες. Για τον σκοπό αυτό σχεδιάστηκε και εξομοιώθηκε η δίπλευρη τυπωμένη κεραία παπιγιόν αλλά και η τυπωμένη ελλειπτική διπολική κεραία. Στο έκτο κεφάλαιο, μελετώνται οι τυπωμένες κεραίες σχισμής. Για τον σκοπό αυτό σχεδιάστηκαν και εξομοιώθηκαν δύο ελλειπτικές κεραίες σχισμής τροφοδοτούμενες η πρώτη από μικροταινιακή γραμμή και η δεύτερη από ομοεπίπεδο κυματοδηγό. Επιπλέον οι γραμμές μεταφοράς των κεραιών καταλήγουν σε stub διαφορετικού σχήματος. Στο έβδομο, τέλος, κεφάλαιο γίνεται μια συνοπτική παρουσίαση των αποτελεσμάτων, ενώ παρατίθενται συμπεράσματα και προτάσεις για μελλοντική ενασχόληση πάνω στο θέμα των τυπωμένων υπερευρυζωνικών κεραιών. / The present diploma thesis will focus on the study, design and simulation of printed Ultrawideband antennas. These antennas are suitable for high data rate wireless personal area networks. The first chapter includes key definitions of antenna theory. Moreover, the program ADS Momentum that was used during the simulations is presented. In the second chapter, we present the key attributes, the advancement, the advantages and the most crucial applications of UWB technology. The third chapter depicts the desirable attributes of UWB antennas. In addition, some common matching, and element design techniques are presented. Furthermore, Ultrawideband antenna categories are introduced. Finally, some interesting examples of printed Ultrawideband antennas are mentioned. In the fourth chapter, printed UWB monopole antennas are being studied. For this purpose two printed circular disc monopole antennas were designed and simulated. The former fed by a microstrip line and the latter by a coplanar waveguide. In the fifth chapter, printed UWB dipole antennas are being studied. A double sided printed bow tie antenna and an elliptical dipole antenna were designed and simulated. In the sixth chapter, printed UWB slot antennas are being studied. For this purpose two printed elliptical slot antennas were designed and simulated. The former fed by a microstrip line and the latter by a coplanar waveguide. Finally, the seventh chapter includes a comparison of the simulated antennas along with conclusions and proposed future work.

Many emerging applications call for wideband analog-to-digital converters and some require medium-to-high resolution. Incorporating such ADCs allows for shifting as much of the signal processing tasks as possible to the digital domain, where more flexible and programmable circuits are available. However, realizing such ADCs with the existing single stage architectures is very challenging. Therefore, parallel ADC architectures such as time-interleaved structures are used. Unfortunately, such architectures require high-speed high-precision sample-and-hold (S/H) stages that are challenging to implement. In this thesis, a parallel ADC architecture, namely, the frequency-translating hybrid ADC (FTH-ADC) is proposed to increase the conversion speed of the ADCs, which is also suitable for applications requiring medium-to-high resolution ADCs. This architecture addresses the sampling problem by sampling on narrowband baseband subchannels, i.e., sampling is accomplished after splitting the wideband input signals into narrower subbands and frequency-translating them into baseband where identical narrowband baseband S/Hs can be used. Therefore, lower-speed, lower-precision S/Hs are required and single-chip CMOS implementation of the entire ADC is possible. A proof of concept board-level implementation of the FTH-ADC is used to analyze the effects of major analog non-idealities and errors. Error measurement and compensation methods are presented. Using four 8-bit, 100 MHz subband ADCs, four 25 MHz Butterworth filters, two 64-tap FIR reconstruction filters, and four 10-tap FIR compensation filters, a total system with an effective sample rate of 200 MHz is implemented with an effective number of bits of at least 7 bits over the entire 100 MHz input bandwidth. In addition, one path of an 8-GHz, 4-bit, FTH-ADC system, including a highly-linear mixer and a 5th-order, 1 GHz, Butterworth Gm-C filter, is implemented in a 90 nm CMOS technology. Followed by a 4-bit, 4-GHz subband ADC, the blocks consume a total power of 52 mW from a 1.2 V supply, and occupy an area of 0.05 mm2. The mixer-filter has a THD ≤ 5% (26 dB) over its full 1 GHz bandwidth and provides a signal with a voltage swing of 350 mVpp for the subsequent ADC stage.

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