Localization is one of the most interesting research areas in wireless networks. It is mostly used for tracking and monitoring applications such as traffic monitoring, search and rescue, navigation and so on. A good quality system can be defined from its accuracy when operating in severe interference environments that contaminate the signals and therefore reduce the system performance. The main issue for localization is channel propagation, e.g., line of sight or non-line of sight channel which should be studied in order to improve the system efficiency.    In order to perform a localization, most algorithms use two steps: ranging and positioning. For ranging, the two popular techniques that are widely used for distance measurement are received signal strength (RSS) and time of arrival (TOA). RSS ranging technique uses the power of the received signals to identify the distance between a transmitter and a receiver. TOA ranging technique uses time of the signal traveling between a transmitter and a receiver to identify the distance, thus it requires synchronization. The measurements are processed by using a localization algorithm afterwards. However, these techniques suffer from multipath fading and other errors, so there always exists error in the estimated position.    In this thesis, TOA ranging technique is used for different estimation methods. Simulation results are performed using MATLAB, while the real results are obtained from Pozyx indoor positioning platform. Several estimation algorithms comprising of maximum likelihood (ML), linearized least square (LLS), weighted centroid (WC), and fingerprinting (FP) are studied in detail. The testing area is indoor environment which is suitable for LOS, NLOS and combined situations. The measured data is then used for ranging and localization. We concentrate on comparing and discussing these results in this thesis.

This thesis discusses microstrip circuits and components with a slotted area on the ground plane. In recent years, various slot geometries have been placed on the ground plane with the purpose of reducing harmonics, producing frequency pass/stop-bands, and enhancing coupling effects. Among several ground slot geometries, a dumbbell shaped slot (DSS) is attractive because of its simple structure and easy analysis. The DSS and its applications to RF/microwave filters are studied and discussed. A lumped equivalent circuit model of the dumbbell shaped ground slot is introduced by utilizing resonator and filter theories. The accuracy of the equivalent circuit model is demonstrated through the comparison of circuit simulations and measurements. A lowpass filter (LPF) using slotted ground structure (SGS) with dumbbell shape is designed and measured to validate its theories. By using SGS techniques presented in this thesis, some other RF/microwave components such as a periodic structure, ultra-wideband bandpass filter (UWB-BPF), and rectenna with SGS-LPF are designed and tested.

This thesis discusses microstrip circuits and components with a slotted area on the ground plane. In recent years, various slot geometries have been placed on the ground plane with the purpose of reducing harmonics, producing frequency pass/stop-bands, and enhancing coupling effects. Among several ground slot geometries, a dumbbell shaped slot (DSS) is attractive because of its simple structure and easy analysis. The DSS and its applications to RF/microwave filters are studied and discussed. A lumped equivalent circuit model of the dumbbell shaped ground slot is introduced by utilizing resonator and filter theories. The accuracy of the equivalent circuit model is demonstrated through the comparison of circuit simulations and measurements. A lowpass filter (LPF) using slotted ground structure (SGS) with dumbbell shape is designed and measured to validate its theories. By using SGS techniques presented in this thesis, some other RF/microwave components such as a periodic structure, ultra-wideband bandpass filter (UWB-BPF), and rectenna with SGS-LPF are designed and tested.

Thesis (Ph. D.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 112-117). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2006. / Printout. Includes bibliographical references (leaves 58-59). Also available on the World Wide Web.

Ultra-Wideband (UWB) wireless communication systems employ large bandwidths and low transmitted power spectral densities, and are suitable for operation as underlay systems which reuse allocated spectrum. The subject of this dissertation is Multiband Orthogonal Frequency Division Multiplexing (MB-OFDM) UWB for high data-rate communication. We address four main questions: (1) What are the theoretical performance limits and practical system performance of MB-OFDM? (2) What extensions can be used to increase the system power efficiency and range? (3) Is it possible to estimate the system error rate without resorting to time-consuming simulations? and (4) What is the effect of interference from narrowband systems on MB-OFDM, and can this interference be mitigated? As for questions 1 and 2, we investigate the MB-OFDM performance, and propose system enhancements consisting of advanced error correcting codes and OFDM bit-loading. Our methodology includes the development of information-theoretic performance measures and the comparison of these measures with performance results for MB-OFDM and our proposed extensions, which improve the power efficiency by over 6 dB at a data rate of 480 Mbps. To address question 3, we develop novel analytical methods for bit error rate (BER) estimation for a general class of coded multicarrier systems (of which MB-OFDM is one example) operating over quasi-static fading channels. One method calculates system performance for each channel realization. The other method assumes Rayleigh distributed subcarrier channel gains, and leads directly to the average BER. Both methods are also able to account for sum-of-tones narrowband interference. As for question 4, we first present an exact analysis of the uncoded BER of MB-OFDM in the presence of interference from incumbent systems such as IEEE 802.16 ("WiMAX"). We also present a Gaussian approximation for WiMAX interference, and establish its accuracy through comparison with exact analysis and simulations. We then propose a two-stage interference mitigation technique for coded MB-OFDM, consisting of interference estimation during silent periods, followed by metric weighting during decoding, which provides substantial gains in performance in return for modest increases in complexity, and without requiring any modifications to the MB-OFDM transmitter.

 This thesis focuses on three research topics on the design about planar ultrawide-band (UWB) monopole antennas, namely, the design of band notches for UWB monopole antennas, the ground-plane and cable effects on the measurement of compact UWB monopole antennas, and the design of a chipless UWB radio-frequency-identification (UWB-RFID) system. The designs of single, dual, triple and quadruple band-notched UWB monopole antennas using coplanar waveguide (CPW) resonators, quarter-wavelength (λ/4)-resonators and meander lines (MLs) are presented. The center frequencies and bandwidths of the individual notches in all these designs can be adjusted independently by varying the dimensions of the resonators. Studies of the designs are carried out by computer simulations using the EM software tool, CST MWS. For verification of the simulation results, these antennas are fabricated and measured using the antenna measurement system, Satimo Starlab. The frequency-domain performances, in terms of return loss, peak gain, efficiency and radiation pattern, and the time-domain performances, in terms of pulse responses and fidelity, are investigated by simulation and measurement. Results show that these UWB antennas have approximately omnidirectional radiation patterns with good band-notched characteristics and fidelities of more than 85% in the pulse responses. Results of studies show that, using a small ground plane in the design of the compact UWB antennas, there will be larger discrepancies between the measured and simulated radiation patterns, radiation efficiencies and peak gains at low frequencies. The discrepancies are due to diffraction of the electric fields at the edges of the small ground plane, which leads to currents flowing back to the measuring cable and hence secondary radiation. Computer simulation and measurement are used to study the ground-plane effects using a group of nine UWB antennas. These antennas have the same radiator but with rectangular ground planes of different sizes. Results show that the width of the ground plane affects the efficiency more than the length, while the length affects the lower cut-off frequency. The cable effects are further studied by modeling the measuring cables. Results show that, by using the cable model, the simulation and measurement efficiencies agree extremely well. The design of a novel chipless UWB-RFID system is presented. The system employs uniplanar chipless tags and a pair of high-gain reader antennas. The chipless tag is composed of two UWB monopole antennas connected by a CPW. Tag identification (ID) is represented by a spectral signature in the UWB and created by using a multi-resonator embedded on the CPW. Detection of spectral signature is based on only the amplitude of the spectral signature. Vertically and horizontally polarized signals are used to reduce mutual coupling between the uplink and downlink signals. Further reduction of the mutual coupling is achieved by using a copper plate in the reader to separate the uplink and downlink signals. Results of studies in an anechoic chamber show that the proposed RFID system can achieve a read range larger than 30 cm, indicating that the proposed system has great potentials for short-range item tracking at low-cost. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Ultra-Wideband (UWB) wireless communication systems employ large bandwidths and low transmitted power spectral densities, and are suitable for operation as underlay systems which reuse allocated spectrum. The subject of this dissertation is Multiband Orthogonal Frequency Division Multiplexing (MB-OFDM) UWB for high data-rate communication. We address four main questions: (1) What are the theoretical performance limits and practical system performance of MB-OFDM? (2) What extensions can be used to increase the system power efficiency and range? (3) Is it possible to estimate the system error rate without resorting to time-consuming simulations? and (4) What is the effect of interference from narrowband systems on MB-OFDM, and can this interference be mitigated? As for questions 1 and 2, we investigate the MB-OFDM performance, and propose system enhancements consisting of advanced error correcting codes and OFDM bit-loading. Our methodology includes the development of information-theoretic performance measures and the comparison of these measures with performance results for MB-OFDM and our proposed extensions, which improve the power efficiency by over 6 dB at a data rate of 480 Mbps. To address question 3, we develop novel analytical methods for bit error rate (BER) estimation for a general class of coded multicarrier systems (of which MB-OFDM is one example) operating over quasi-static fading channels. One method calculates system performance for each channel realization. The other method assumes Rayleigh distributed subcarrier channel gains, and leads directly to the average BER. Both methods are also able to account for sum-of-tones narrowband interference. As for question 4, we first present an exact analysis of the uncoded BER of MB-OFDM in the presence of interference from incumbent systems such as IEEE 802.16 ("WiMAX"). We also present a Gaussian approximation for WiMAX interference, and establish its accuracy through comparison with exact analysis and simulations. We then propose a two-stage interference mitigation technique for coded MB-OFDM, consisting of interference estimation during silent periods, followed by metric weighting during decoding, which provides substantial gains in performance in return for modest increases in complexity, and without requiring any modifications to the MB-OFDM transmitter.

A new Ultra-Wideband (UWB) pattern diversity antenna is proposed, designed and investigated in this thesis. The antenna is capable of radiating in directive and omni-directional modes. Three different versions of the design are studied to show the performance for different applications. The first design consists of a single radiating element fed from two sides by coaxial probes over a shaped ground plane. In-phase excitation of the ports produces omni-directional radiation patterns and out-of-phase excitation results in directive radiation in the boresight of the antenna. The shape of the radiator is a disk, which is modified in geometry to improve the isolation of the ports. The antenna shows impedance bandwidth from 6.8 GHz to more than 15 GHz. The second design is a dual-element version of the same antenna to equalize the radiation patterns in the E- and H-planes. The antenna requires four ports and has an impedance bandwidth from 7.4 GHz to more than 15 GHz. A microstrip power divider is then included, in the third design, which in addition to decreasing the number of extra circuits for feeding, decreases the lower frequency to 4.5 GHz, without changing the radiation patterns significantly throughout the bandwidth. A prototype of this antenna was fabricated and measured, and the results are presented. In the fifth chapter, an electromagnetic polarization filter is designed for the single element UWB antenna, to reduce the cross-polarization level. 7 dB reduction in the maximum level of cross-polarization is achieved, throughout the frequency band 8 - 11 GHz. The following chapter is dedicated to the study and performance of the microstrip-fed UWB antenna, when used as a feed for prime-focus reflectors. It is shown that the designed antenna is capable of feeding the reflector with efficiency as high as 75%, and more than 60%, over a wide bandwidth of 5.5 - 9 GHz.

Thesis (MS)--Montana State University--Bozeman, 2009. / Typescript. Chairperson, Graduate Committee: Richard Wolff. Includes bibliographical references (leaves 109-112).