Ultra-Wideband ¡}UWB¡~Communication Technology is one of the potential technologies in indoor wireless communication applications. Because of the property of fine resolution of transmitted signal by UWB, it is powerful on indoor location applications. In the first place, we need to estimate the time of arrival based on the wireless location applications. Whether synchronization between the template signals and received signals affects directly the SNR of the estimator output and decreases the ranging accuracy. Because of the transmitted signal is the type of impulse radio for UWB system, it is more important on the time accuracy of the internal oscillator. In the thesis, we utilize the Delay-Locked Loop ¡}DLL¡~ structure with Self-tuning function to reduce the timing jitter in the internal oscillator. We can improve the stability in the tracking loop and utilize multipath canceller to cancel the multipath interference in the indoor environment. When reaching synchronization between the template signal and received signal by using the tracking loop, we can improve ranging accuracy and increase location precision according to the received signal.

Compared with Nd:YAG, the traditional high power solid state laser gain medium, Yb:YAG has less quantum defect, no excited state absorption, and longer fluorescence lifetime, which makes it suitable for Q-switched laser. In addition, concentration quenching is absent in Yb:YAG, higher concentration of active ion makes the thickness of gain medium thinner. For ring cavities, the necessity of symmetrical beam path is important, a thinner Yb:YAG crystal can reduce the shift of optical beam path and avoids cavity unstability. Thus, Yb:YAG is suitable for the two-mirror ring cavity. In this study, a compact and efficient Yb:YAG ring laser with 50.3% slope efficiency was demonstrated. And the Yb:YAG ring laser performances influenced by thermal effect was analyzed and compared to that of Nd:YAG ring laser. The polarization of ring lasers with different configurations were also discussed. In manufacturing process, the coating design on gain medium and laser mirrors were introduced. The advantages of passively Q-switched laser are efficient, compact, simple setup and no complicated driving circuits. They make passively Q-switched laser suitable for various applications, such as nonlinear optics, medical treatment, micromachining, material processing, and range finder. Due to spontaneous noise from the gain medium, conventional passively Q-switched laser has large timing jitter. This study is to build up a passively Q-switched Yb:YAG/Cr4+:YAG ring laser with lower timing jitter. At present, a Q-switched ring laser with a peak power of 208 W and a pulse width of 33 ns, was developed. Its slope efficiency is 18.1% with a timing jitter of 11.9%. To our knowledge, this is the first passively Q-switched Yb:YAG/Cr4+:YAG ring laser.

In order to understand the effects of structurally induced line of sight (SILOS) jitter (vibration) and to predict its effects on optical system performance, a simple and practical vibratory model and software are developed by using discrete and finite element modeling techniques. For an existing simple optical system, discrete and FE dynamic models are constructed and they are validated by modal tests for the frequency range of interest. In order to find material properties of adhesive, which is used in optical system, a simple test is constructed and these properties are found by using a single degree of freedom model. The effects of vibration on the system performance are investigated under random vibration load conditions by using the software developed. It is concluded that the analytical model suggested can successfully be used in preliminary design stage of a simple optical system when the optical housing and lens behave rigidly in the frequency range of interest. The optical performance prediction software combines the optical element tolerances and displacements in order to determine the optical performance.

Control algorithm is developed for a satellite with flexible appendages to achieve a good pointing performance. Detailed modeling activity was carried out that consists of sensor and actuator models, disturbances and system dynamics. Common hardware found in the spacecraft such as reaction wheels, gyroscopes, star trackers etc. were included in the model. Furthermore, the Newton-Euler method is employed for the derivation of multi-body equations of motion. Evaluation of the pointing accuracy with proper pointing performance metrics such as accuracy, jitter and stability during slew maneuvers are obtained through simulations. Control strategies are proposed to improve pointing performance.

Most proposed regulation methods do not take advantage of the state information of the underlying scheduler, resulting in a waste of resources. We propose a dynamic regulation approach in which the regulation function is modulated by both the tagged stream's characteristics and the state information fed-back from the scheduler. The transmission speed of a regulator is accelerated when too much traffic has been sent to the scheduler by the other regulators or when the scheduler's queue is empty. As a result, the mean delay of the traffic can be reduced and the scheduler's throughput can be increased. Since no complicated computation is involved, our approach is suitable for the use in high-speed networks.

Multimedia performances, uniting music and interactive images, are a unique form of entertainment that has been explored by artists for centuries. This audio-visual combination has evolved from rudimentary devices generating visuals for single instruments to cutting-edge video image productions for musical groups of all sizes. Throughout this evolution, a common goal has been to create real-time, audio-responsive visuals that accentuate the sound and enhance the performance. This paper explains the creation of a project that produces real-time, audioresponsive and artist interactive visuals to accompany a live musical performance by a symphony orchestra. On April 23, 2006, this project was performed live with the Brazos Valley Symphony Orchestra. The artist, onstage during the performance, controlled the visual presentation through a user interactive, custom computer program. Using the power of current visualization technology, this digital program was written to manipulate and synchronize images to a musical work. This program uses pre-processed video footage chosen to reflect the energy of the music. The integration of the video imagery into the program became a reiterative testing process that allowed for important adjustments throughout the visual creation process. Other artists are encouraged to use this as a guideline for creating their own audio-visual projects exploring the union of visuals and music.

近年來通訊網路的進步與寬頻網路的發展，使得更多新型的網路服務迅速應運而生，對網路服務的品質(QoS)也更加要求。眾多新興的應用服務中，即時性的應用服務(real-time traffic)，像是Voice over IP (VoIP)以及video on demand (VoD)，對於封包的傳遞延遲時間(delay time)以及抖動(jitter)具有嚴格的要求，router在處理即時性封包時，並非僅將封包快速送出即可，而須在一定的延遲時間內送出。本研究在BBQ﹙Budget-Base QoS﹚的架構下，發展一套簡單而有效的方法，在封包所經過的每一個router時，根據其緊急程度、服務等級及網路處理能力賦予合適的profit function，再對封包重新排程以獲得最大的profit，期望減小在接收端的jitter絕對值總和，進而增進網路的效能。在此我們設計了四種profit function配合Greedy演算法在兩種不同的router架構上調整封包傳送順序，並利用網路模擬工具NS2在即時性訊務分為單一服務等級及雙服務等級的情況下評估我們方法的效能，證明我們的方法較既有的方法更可以有效控制jitter，且能對不同的服務等級做適當的差異化處理以提高整體服務滿意度。 / With fast growth of Internet traffic and applications, real-time streaming applications have attracted significant attention in the current Internet society. Novel real-time Internet applications such as Voice over IP (VoIP) and video on demand (VoD), have stringent delay and jitter requirements. Under these requirements a router not only have to forward real-time packet as fast as possible, it also have to accomplish the job within a time bound. Our research is based on BBQ﹙Budget-Based QoS﹚management architecture. In order to minimize the jitter of real-time services, we propose a new jitter control mechanism that uses per-hop packet scheduling. Four profit function are designed to represent different scheduling preferences. When a packet gets into a router, the router will assign a profit function based on its timeness and the class of service. The scheduler will re-schedule their order in output queue aiming to maximize total profit. Finally we evaluate our proposed mechanism by NS2 simulator in two situations, single real-time service class and two real-time service classes. Simulation results show that by using our approach the performance is better than other approaches. And we investigate the performance of the combination of profit function in handling multiple classes of service.

As users become more comfortable using IEEE 802.11 Wireless Local Area Networks, the need for quality of service is becoming more important because of the lack of support in current standards and the increase of multimedia traffic over the Internet. The IEEE 802.11 working group has recognized this fact proposing the Enhanced Distributed Channel Access (EDCA), a priority-based distributed scheme meant to provide service differentiation. EDCA relies on either different Arbitrary Interframe Space (AIFS), or Contention Window (CW) parameters, or both to provide service differentiation. In this thesis, a performance evaluation of the EDCA using five different combinations of the above mentioned parameters is included and compared to the current DCF (Distributed Coordination Function) standard, which is used as the base case. Simulation results show that simpler schemes based on one parameter alone can provide good average service differentiation. However, only multiparameter schemes provide the average and instantaneous high throughput and low delay values needed to support streaming applications. Starvation is a problem spanning all these schemes. It is especially more pronounced in schemes using combinations of parameters. In this thesis, a measurement-based admission control mechanism is proposed to overcome the above stated problems. The admission control mechanism uses an algorithm that admits a flow depending on the jitter values for high priority traffic and the throughput of the low priority traffic. It also allows the administrator to set the bandwidth sharing policy between the high priority traffic and low priority traffic. Results show that the admission control mechanism not only protects existing high priority flows from jitter and low priority flows from starvation, but also improves upon the network utilization.

Οι γεννήτριες τυχαίων αριθμών (ΓΤΑ) βρίσκονται στη ζωή του ανθρώπου εδώ και χιλιάδες χρόνια. Η πιο συχνή εφαρμογή τους είναι σε παιχνίδια που εμπεριέχουν τύχη, θεωρείστε για παράδειγμα το ζάρι που αποτελεί μια από τις πιο παλιές και πιο γνωστές γεννήτριες τυχαίων αριθμών. Ωστόσο με την πρόοδο της τεχνολογίας βρήκαν εφαρμογή και σε άλλους τομείς και κυρίως στην κρυπτογραφία, όπως για παράδειγμα στην ασφαλή μεταφορά δεδομένων στο διαδίκτυο ή στη διατήρηση της ασφάλειας ενός τοπικού δικτύου. Στα πλαίσια αυτής τη διπλωματικής θα δούμε τις κατηγορίες στις οποίες χωρίζονται οι ΓΤΑ καθώς επίσης και διάφορες πηγές τυχαιότητας γι’ αυτές. Στη συνέχεια θα επικεντρωθούμε στις Γεννήτριες Πραγματικά Τυχαίων Αριθμών και την εφαρμογή τους σε ολοκληρωμένα κυκλώματα όπως τα FPGA και θα δούμε κατάλληλες τεχνικές για την υλοποίηση τους. Έπειτα παρουσιάζουμε τη δομή και τη λειτουργία δύο γεννητριών που βασίζονται στην τεχνική που αξιοποιεί το jitter των ταλαντωτών. Η βασική τους διαφορά, η οποία κατ’ επέκταση επηρεάζει και το συνολικό σχεδιασμό, είναι ότι η μία έχει έναν αργό και ένα γρήγορο ταλαντωτή, ενώ η άλλη δύο γρήγορους ταλαντωτές. Στο στάδιο της υλοποίησης θα χρησιμοποιήσουμε τη γλώσσα περιγραφής υλικού VHDL και θα δούμε τη συμπεριφορά των σχεδιασμών μας όσον αφορά την επιφάνεια που καταλαμβάνουν και την ισχύ που καταναλώνουν για συγκεκριμένες τεχνολογίες FPGA. Επίσης θα ελέγξουμε τη στατιστική ποιότητα των ακολουθιών bit που παράγουν οι γεννήτριες μας για να επαληθεύσουμε την αποτελεσματική λειτουργία των σχεδιασμών μας. Τέλος θα συγκρίνουμε τις δύο ΓΠΤΑ που σχεδιάσαμε στους τομείς που μόλις αναφέραμε. / -

The Phase Locked Loops (PLLs) are widely used in contemporary electronic systems for frequency synthesis, clock recovery, frequency multiplication and other purposes. Because of continuous increase in operating frequency of clocking systems the requirements on the clock spectral purity and low jitter became very demanding and are one of major designers' concerns.Frequency synthesizers used in microprocessors are integrated on the same substrate as the rest of the circuit and thus suffer from a substantial switching noise injected into global supply and ground busses. Usually when the reference signal comes from a crystal oscillator, VCO becomes a main source of phase noise. A designer of VCO needs to determine the best circuit structure by considering different prototypical perturbations scenarios and predicting the worst case and jitter response when the perturbation signals are switched on and off. Therefore the time efficient estimation of the jitter effects resulting from many shapes, frequencies and phases of perturbation is critical.The presented dissertation demonstrates simulation methodology for rapid estimation of jitter in oscillators, particularly in VCOs, caused by perturbation sources such as power supply and substrate couplings. The methodology is also extended to these types of PLLs in which the VCO instability is a main contributor to the output timing jitter.Simulation of oscillatory circuits is strongly effected by the round-off errors. Special technique was developed to eliminate these effects.The technique is applicable for predicting timing non-idealities for arbitrary perturbation shapes, frequencies and phases. Different jitter metrics can be easily extracted for all important perturbation scenarios.The methodology utilizes the new concept of the transient multi-cycle Voltage Impulse Sensitivity Function (VISF), which has been developed in the dissertation. It contains information about sensitivity of oscillator to noise injection and also allows for efficient prediction of the transient effects caused by switching on and off the perturbation sources. The methodology offers efficiency and great simplicity of use, which frees designers from complicated, time consuming analysis of data generated by a simulator. The very involved postprocessing of simulation data can be fully automated.