Ultra-Wideband impulse radio (UWB-IR) technology is an attractive method on multi-user for high data rate transmitting structures. In this thesis, we use the ultra wideband (UWB) signal that is modulated by the time-hopping spread spectrum technique in a wireless multiple access environments, and discuss the influences of multiple access interference. We discuss two parts of the influences of multiple access interference in this thesis. The first, we analyze the multiple access interferences on the conventional correlation receiver, and discuss the influences by using the time hopping code on different multiple access structures. The second, we know that the performances of user detection and system capacity would be degraded by the conventional correlation receiver in the multiple access channels. The Probabilistic Data Association(PDA) multi-user detection technology can eliminate multiple access interferences in this part. We will use this method to verify the system performance through the computer simulations, and compare to other multi-user detectors with convention correlation receivers. Finally, the simulation results show that the performance of the PDA multi-user detections is improved when the system is full loaded.

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.

Ultra Wideband (UWB) signal can offer an accurate location service in wireless sensor networks because its high range resolution. Target tracking by multiple sensors can provide better performance, but the centralized algorithms are not suitable for wireless sensor networks. In additional, the non line of sight (NLOS) propagation error leads to severe degradation of the accuracy in location systems. In this thesis, NLOS identification and mitigation technique utilizing modified biased Kalman filter (KF) is proposed to reduce the NLOS time of arrival (TOA) errors in UWB environments. We combine the modified biased Kalman filter with sliding window to identify and mitigate different degree of NLOS errors immediately. In order to deal with the influence of inaccurate NLOS angle of arrival (AOA) measurements, we also had a discussion on AOA selection and fusion methods. In the distributed location structure, we used the extended Information filter (EIF) to process the formulated time difference of arrival (TDOA) and AOA measurements for the target positioning and tracking. Instead of using extended Kalman filter, extended Information filter can assimilate selected AOA easily without dynamic dimensions. The sensors are divided into different groups for distributed TDOA/AOA location to reduce computation and then each group can assimilate information from other groups easily to maintain precise location. The simulation results show that the proposed architecture can mitigate NLOS errors effectively and improve the accuracy of target positioning and tracking from distributed location and data fusion in wireless sensor networks.

The objective of this thesis is aimed at the design of low noise amplifier (LNA) for an ultra-wideband (UWB) receiver system using standard 0.18um CMOS process. A two amplified stage topology is proposed in the low noise amplifier. The first stage introduces inductively source degeneration and resistive-feedback, it can achieve wideband input impedance matching. The second stage introduces traditional CS configuration, it can improve the forward gain (S21). The second stage also used L-C section for output match. In order to improve the gain at high frequency, we introduces the series peaking between the first stage and second stage. The total power dissipation of the low noise amplifier is about 24.3mW at power supply 1.5 volt and the chip size is 1.283*1.008mm2. The simulated result shows that S11 is under -8dB, S22 is under -10dB, the forward gain S21 is 12.6dB~15.3dB at 3.1-10.6GHz, the reverse isolation S12 is under -30dB, and the noise figure is 3.24dB~4.84dB.

Novel techniques for high-performance wireless power transmission and data interfacing with implantable medical devices (IMDs) were proposed. Several system- and circuit-level techniques were developed towards the design of a novel wireless data and power transmission link for a multi-channel inductively-powered wireless implantable neural-recording and stimulation system. Such wireless data and power transmission techniques have promising prospects for use in IMDs such as biosensors and neural recording/stimulation devices, neural interfacing experiments in enriched environments, radio-frequency identification (RFID), smartcards, near-field communication (NFC), wireless sensors, and charging mobile devices and electric vehicles. The contributions in wireless power transfer are the development of an RFID-based closed-loop power transmission system, a high-performance 3-coil link with optimal design procedure, circuit-based theoretical foundation for magnetic-resonance-based power transmission using multiple coils, a figure-of-merit for designing high-performance inductive links, a low-power and adaptive power management and data transceiver ASIC to be used as a general-purpose power module for wireless electrophysiology experiments, and a Q-modulated inductive link for automatic load matching. In wireless data transfer, the contributions are the development of a new modulation technique called pulse-delay modulation for low-power and wideband near-field data communication and a pulse-width-modulation impulse-radio ultra-wideband transceiver for low-power and wideband far-field data transmission.

Historical, well developed, procedures for RF design have minimal emphasis on exploring the third dimension due to the difficulty of fabrication. Recent material advancements applicable to 3D printing have brought about low-loss thermoplastics with excellent mechanical properties. Research into depositing conductive inks onto arbitrary 3D shapes has achieved resolutions better than 50 μm with conductivity values approaching that of copper cladding. The advancements in additive manufacturing have improved reliability and repeatability of three dimensional designs while decreasing fabrication time. With this design approach other considerations, such as stability and strength, can be concentrated on during the structure design to realize new shapes. The next step in the future of RF research will encompass designing and further understanding the benefits and consequences of using all three dimensions. This could include meandering an antenna element around other electronic components to make the overall package size smaller or integrating an antenna array into a wing. The design and analysis of the periodic spiral antenna (PSA) takes a look at a specific case of full volume utilization. In this application meandering in the z-dimension allowed the design to become smaller and more efficient than what is achievable with planar methods. This thesis will go into detail on the characterization of the periodic spiral antenna. To exemplify the benefits of meandering in the z-dimension a loop antenna is presented and benchmarked against other miniaturization techniques. Measured results of two different PSA models are presented and remarks on improving fabrication are given. When an antenna is used as a transmitter incident power will cause thermal generation so a study was conducted to understand how material properties can govern the amount of heat generated.

Linearity enhancement, especially within the front end of a wireless receiver IC design, is highly desirable since it allows the front-end to withstand strong interferers from co-existing communication standards or other wireless radiators. We propose an interferer suppression method based on feed-forward cancellation that uses an injectionlocked oscillator (ILO) to extract the interferer from the incident spectrum. The technique is expected to be useful in environments where a strong narrowband interferer appears along with a wideband desired signal, such as ultra-wideband (UWB) and emerging cognitive-radio applications. The ILO is further embedded within a phase-locked loop which provides several advantages including ILO center frequency self tuning and automatic phase alignment between the main signal path and the auxiliary path. An IC that uses this approach is implemented in a UMC 0.18[mu]m RFCMOS process. In measurement, the chip demonstrates 20dB suppression for phase and frequency modulated interferers while maintaining around 18dB power gain and noise figure below 5dB, measured with an off-chip balun for the desired signal. Techniques for canceling amplitude modulated interferers, though not included in the integrated circuit, were also demonstrated with an off chip amplitude control loop. Over 20dB rejection was obtained with AM interferers with properly scaled envelop signal applied to the ILO bias port. A second LNA was connected in cascade with the system to emulate the input stage of a down-conversion mixer and the cascaded P1dB was improved over 16dB with cancellation on. Gain compression above 13dB was also observed when auxiliary path was disabled, at the same input level as the P1dB with cancellation applied. / text

The wide bandwidth employed in the UWB system allows for high data-rate communications, while its broadband nature requires it to coexist with other systems. For instance, several communication systems, such as digital TV, wireless LANs, WiMAX, and satellite receivers, utilize spectrum that is in the UWB band. According to Federal Communications Commission (FCC) regulations, the power spectral density (PSD) of UWB devices for communication applications is limited to less than -41.25dBm/MHz in the 3.1-10.6GHz frequency band, to minimize the impact of UWB on other systems. The impact of narrowband signals on UWB systems can also be significant, even though these signals may occupy a small part of the UWB spectrum, due to their much larger power. The performance and capacity of UWB systems can be significantly degraded by these narrowband interferers. In-band interference can be tolerated by increasing the dynamic-range of the receiver such that the interferers are accommodated within the linear range of the receiver. Alternatively, if the interferers can be avoided altogether, the excessive linearity requirements imposed by the interferers can be relaxed. Such an avoidance mechanism requires the ability to detect interferers. This work presents a low-power and low-cost detector for this purpose that can be employed in multi-band approaches to UWB, including pulse-based schemes, and those employing OFDM. The UWB band is divided into narrower sub-bands in these schemes. During transmission, the carrier hops to a new sub-band every symbol. The detector is designed to provide a profile of interference over the entire UWB spectrum, during each symbol period. This information would be available to the main-path UWB receiver to decide a frequency sequence of sub-band hopping, in order to avoid sub-bands occupied by large interferers. This relaxes the dynamic-range requirement, and hence the power dissipation of the main-path receiver, thus compensating for the extra power dissipation of the detector. The detector is based on a cascade of image-reject downconverter stages. An implementation of the architecture is demonstrated in a 0.13[mu]m CMOS process. / text

This thesis presents the designs of Ultra-wideband (UWB) monopole antennas, textile monopole antennas and transparent UWB textile antennas using planar technology for body-centric wireless communications (BCWC). A planar antenna designed using offset-fed and slotted ground plane to extend the operating bandwidth for the industrial, scientific and medical (ISM)band and UWB is proposed. Results show that the antenna can achieve a bandwidth from 2.38 to 14.5 GHz with omni-directional radiation patterns in the E-plane. Agroup of nine planar UWB monopole antennas using different radiator shapes such as triangle, rectangle, square, annual ring, circle, horizontal ellipse, vertical ellipse, pentagon and hexagon for BCWC is studied using computer simulation and measurement. Results show that the monopole antenna having a vertical-elliptical-shape radiator has a relatively better performance than other monopole antennas. Three textile antennas fabricated on fabric materials are studied. The first design is a triple-band textile antenna for wireless-local-area network (WLAN) and worldwide interoperability for microwave access (WiMAX) wireless communication applications. The radiator is composed of two branches and a short stub to generate the resonances at about 2.45, 3.5 and 5.5 GHz, respectively. Simulated and measured results show that the three frequency bands can be set independently. The second design is an UWB antenna consisting of a circular radiator, a tapered feed line and a slotted ground plane. Results show that the antenna can achieve a bandwidth of 3 to 12 GHz. The third design is a compact belt-loop UWB antenna with microstrip-fed. The antenna has a simple elliptical-shaped radiator, a three-step staircase on both sides of the feed line and a slot on the ground plane. It has a very compactsize of 11×40=440 mm2and can still achieve a bandwidth of 3.1 to 12.8 GHz. To emulate the on-body conditions, the two UWB antennas are studied in the bending and crumpling conditions due to the curvature of human body. Results show that both UWB textile antennas have quite stable performances throughout the UWB band. The two UWB textile antennas are re-designed using a transparent conductive film (TCF)as the radiator and ground plane on fabric substrate. Results show that the measured reflection coefficients of transparent antennas agree well with the simulated results. However, the measured radiation patterns have large discrepancies with the simulated results, which are mainly due to the uncertain electric properties of TCF in radio frequency. Results show that the antennas have a better performance, in terms ofbandwidth, peak gain and radiation efficiency ,than those of other transparent antennas studied before, making our proposed antennas suitable for body-centric wireless communications. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

In this thesis, a low-profile, high-gain, ultra-wideband (UWB) planar dipole antenna is presented for radar imaging applications. The antenna is loaded with open complementary double concentric split-hexagonal-ring resonators (LC tank) and chip resistors, and backed with a novel double-layer FSS reflector for gain enhancement. A broadband microstrip to parallel-plate transformer is designed as the feeding structure of the antenna to provide impedance matching and balanced-to-unbalanced transition. The measurement results show the proposed antenna operates over the frequency bandwidth of 0.65-3.8 GHz with S11< -10 dB (VSWR) and smooth gains in the range of 6.2-9 dBi.