In February 2002, the FCC (2002 a, b) issued a ruling that ultra-wideband (UWB) could be used for data communications as well as for radar and safety applications. UWB system is constrained to have a maximum power transmission of -41 dBm and a bandwidth ranging from 3.1-10.6 GHz. UWB co-exists and does not interfere with the existing narrowband or wideband communication systems in the same spectrum. However, due to its low power in the same bandwidth, UWB is affected by the so-called narrowband (NB) interference. This thesis presents a method to estimate and detect narrowband signals in radio impulse receiver with the intention to eliminate the NB interference. <p>Narrowband bandwidth is very small compared to the bandwidth of UWB therefore the interference can be considered as a single tone. To detect such a tone using conventional techniques is not feasible at least up to this time for UWB as current technology can not support such high data rates. Alternatives way to track down the narrowband signal include using a power spectral density estimation technique called spectrogram. For all cases, the spectrogram at specific frequency range where the narrowband active statistically be larger than its overall average power. Here, a threshold detector is built which reports detection at the frequency range where the narrowband is located if the spectrogram exceeds a threshold value. <p>Upon completing of successful NB detection, the NB signal in the UWB system will be estimated in digital form and cancelled in analog form. The pipelined LMS algorithm is used to estimate the NB signal; the algorithm is implemented using a built-in IP core from the Altera DSP library which can be simulated in either Matlab platform or in FPGA boards. The design correctness has been validated by means of Monte-Carlo simulation and hardware implementation using standard UWB IEEE standard channel models, Time Hopping-Pulse Position Modulation and the rake receiver technique.

In February 2002, the FCC (2002 a, b) issued a ruling that ultra-wideband (UWB) could be used for data communications as well as for radar and safety applications. UWB system is constrained to have a maximum power transmission of -41 dBm and a bandwidth ranging from 3.1-10.6 GHz. UWB co-exists and does not interfere with the existing narrowband or wideband communication systems in the same spectrum. However, due to its low power in the same bandwidth, UWB is affected by the so-called narrowband (NB) interference. This thesis presents a method to estimate and detect narrowband signals in radio impulse receiver with the intention to eliminate the NB interference. <p>Narrowband bandwidth is very small compared to the bandwidth of UWB therefore the interference can be considered as a single tone. To detect such a tone using conventional techniques is not feasible at least up to this time for UWB as current technology can not support such high data rates. Alternatives way to track down the narrowband signal include using a power spectral density estimation technique called spectrogram. For all cases, the spectrogram at specific frequency range where the narrowband active statistically be larger than its overall average power. Here, a threshold detector is built which reports detection at the frequency range where the narrowband is located if the spectrogram exceeds a threshold value. <p>Upon completing of successful NB detection, the NB signal in the UWB system will be estimated in digital form and cancelled in analog form. The pipelined LMS algorithm is used to estimate the NB signal; the algorithm is implemented using a built-in IP core from the Altera DSP library which can be simulated in either Matlab platform or in FPGA boards. The design correctness has been validated by means of Monte-Carlo simulation and hardware implementation using standard UWB IEEE standard channel models, Time Hopping-Pulse Position Modulation and the rake receiver technique.

No description available.

Electrically small, low profile antennas have become the new frontier in wireless communication research. With the pressure to miniaturize wireless communication devices, engineers are turning to small low profile antennas as a way to reduce their antennas and hence their devices. Ideally, one would also like to at least maintain antenna bandwidth and efficiency while reducing size. However, in theory, antenna performance degrades when it is miniaturized—impedance bandwidth decreases with the reduction in antenna size. This thesis investigates the possibility of increasing the input impedance bandwidth without enlarging the volume of the antenna. This thesis attempts to break the fundamental tradeoff between antenna size and bandwidth by loading it with a nonlinear element. First, a brief summary of antenna background definitions is presented. Next, the analytical framework of the thesis is presented using a model of a narrowband antenna. A literature review of various narrowband electrically small antennas is studied, including the pros and cons of the Inverted-F antenna (IFA), Inverted-L antenna (ILA), and the Planar Inverted-F antenna (PIFA).Next, the analysis and the methodology leading to results are discussed and simulated results are presented. Simulated results show that the PIFA is able to achieve a higher bandwidth with a loaded nonlinear element. However, it is difficult to sustain the efficiency of the antenna due to harmonics generated by nonlinearity in the antenna. Results indicate that an increase in nonlinearity tends to generate harmonics which leads to losses in the antenna. / Master of Science

No description available.

Due to the uncertainties introduced by the propagation channel, and RF and mixed signal circuits imperfections, digital communication receivers require efficient and robust signal acquisition algorithms for timing and carrier recovery, and interfer- ence rejection. The main theme of this work is the development of efficient and robust signal synchronization and interference rejection schemes for narrowband, wideband and ultra wideband communications systems. A series of novel signal acquisition schemes together with their performance analysis and comparisons with existing state-of-the- art results are introduced. The design effort is first focused on narrowband systems, and then on wideband and ultra wideband systems. For single carrier modulated narrowband systems, it is found that conventional timing recovery schemes present low efficiency, e.g., certain feedback timing recov- ery schemes exhibit the so-called hang-up phenomenon, while another class of blind feedforward timing recovery schemes presents large self-noise. Based on a general re- search framework, we propose new anti-hangup algorithms and prefiltering techniques to speed up the feedback timing recovery and reduce the self-noise of feedforward tim- ing estimators, respectively. Orthogonal frequency division multiplexing (OFDM) technique is well suited for wideband wireless systems. However, OFDM receivers require high performance car-rier and timing synchronization. A new coarse synchronization scheme is proposed for efficient carrier frequency offset and timing acquisition. Also, a novel highly accurate decision-directed algorithm is proposed to track and compensate the residual phase and timing errors after the coarse synchronization step. Both theoretical analysis and computer simulations indicate that the proposed algorithms greatly improve the performance of OFDM receivers. The results of an in-depth study show that a narrowband interference (NBI) could cause serious performance loss in multiband OFDMbased ultra-wideband (UWB) sys- tems. A novel NBI mitigation scheme, based on a digital NBI detector and adaptive analog notch filter bank, is proposed to reduce the effects of NBI in UWB systems. Simulation results show that the proposed NBI mitigation scheme improves signifi- cantly the performance of a standard UWB receiver (this improvement manifests as a signal-to-noise ratio (SNR) gain of 9 dB).

In recent years, microwave ablation therapy has become widely investigated as an alternative treatment to cancer. This method is one of the newest forms of ablation techniques for the removal of tumors and is minimally invasive compared to alternative treatments. One drawback to many of the current microwave ablation systems is the narrowband nature of the antennas used for the probe, such as dipole antennas. This study aims to compare ablation results of both ultra-wideband and narrowband ablation techniques. An ultra-wideband ablation probe is designed that operates from 400MHz to 2.6GHz and are compared to two designed narrowband ablation probes that operate at 915MHz and 2.4GHz, respectively. These ablation probes are tested in tissue mimicking gels and porcine liver. Provided results for this thesis will include probe designs, simulation results, and ablation experiments.

ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, Nevada / Despite the inherent resistance to narrowband signal interference afforded by GPS spread spectrum modulation, the low level of GPS signals makes them susceptible to narrowband interference. This paper discusses the application of a pre-correlation adaptive temporal filter for stationary and nonstationary narrowband interference suppression. Various adaptive algorithms are studied and implemented. Comparison of the convergence and tracking behavior of various algorithms is made.

<p>Closed loop fuel injection have been in use for two decades but it's not until the recent five years that the wide band lambda sensor have been utilized. The goal is to explain wide band and discrete lambda sensors in a simple but powerful way. Both sensors are modeled by simple mathematics and accounts for Oxygen, Hydrogen and Carbon monoxide influences. The focus is not just on the output from the sensors, but also on the underlying function. This means that all explanations are thorough and methodical. The function of a wide band lambda sensor is more complicated than a discrete type lambda sensor, therefore it's harder to get correct readings. The model of the wide band lambda sensor is used to evaluate different problems in preparation for the development of an observer. Several potential problem sources are tested and investigated, these include calibration error, pressure error, air leak error, gas sensitivity and fuel errors. To evaluate the potential problems and their ability to explain differences between actual lambda and sensor output, two sensors with differing outputs have been used. The final result is implemented in an ECU.</p><p>The models indicate that the difference between the two sensors is most likely explained by different sensitivity for CO, O2 and H2. This can in turn have one or several explanations. It is suggested that different ability to pump oxygen, different nernst cells or even different controllers can cause this. The reason is not investigated further as this would require a very deep research on the two sensors. Because no usable explanation is found an observer that estimates the offset at stoichiometric conditions, where lambda equals one, is constructed. The observer uses the fact that the switch point of a discrete lambda sensor is insensitive to disturbances. The offset calculation is performed in real time on an ECU. Tools for calibration of the observer are also developed. With the observer the error for the two sensors is roughly halved over the whole spectrum and at stoichiometric conditions, which is the normal operation for an engine, the error was too small to measure.</p><p>Although the wide band lambda sensor is a very complex sensor it is shown that it can be understood with simple mathematics and basic knowledge in chemistry. The developed model agrees well with the real sensor for steady state conditions. For transient conditions, however, the model needs to be refined further. The question why the two sensors differ is discussed but the true origin of the cause remains unsolved. The conclusion is that the error can be drastically reduced with just an offset. It is also shown that when building a lambda sensing device the controller is of equal importance as the sensor element itself. This is due to the sensitivity of surrounding factors that the controller must be able to handle. These effects are specially important for engines running at lambda not equal to 1, for example diesel engines.</p>

Closed loop fuel injection have been in use for two decades but it's not until the recent five years that the wide band lambda sensor have been utilized. The goal is to explain wide band and discrete lambda sensors in a simple but powerful way. Both sensors are modeled by simple mathematics and accounts for Oxygen, Hydrogen and Carbon monoxide influences. The focus is not just on the output from the sensors, but also on the underlying function. This means that all explanations are thorough and methodical. The function of a wide band lambda sensor is more complicated than a discrete type lambda sensor, therefore it's harder to get correct readings. The model of the wide band lambda sensor is used to evaluate different problems in preparation for the development of an observer. Several potential problem sources are tested and investigated, these include calibration error, pressure error, air leak error, gas sensitivity and fuel errors. To evaluate the potential problems and their ability to explain differences between actual lambda and sensor output, two sensors with differing outputs have been used. The final result is implemented in an ECU. The models indicate that the difference between the two sensors is most likely explained by different sensitivity for CO, O2 and H2. This can in turn have one or several explanations. It is suggested that different ability to pump oxygen, different nernst cells or even different controllers can cause this. The reason is not investigated further as this would require a very deep research on the two sensors. Because no usable explanation is found an observer that estimates the offset at stoichiometric conditions, where lambda equals one, is constructed. The observer uses the fact that the switch point of a discrete lambda sensor is insensitive to disturbances. The offset calculation is performed in real time on an ECU. Tools for calibration of the observer are also developed. With the observer the error for the two sensors is roughly halved over the whole spectrum and at stoichiometric conditions, which is the normal operation for an engine, the error was too small to measure. Although the wide band lambda sensor is a very complex sensor it is shown that it can be understood with simple mathematics and basic knowledge in chemistry. The developed model agrees well with the real sensor for steady state conditions. For transient conditions, however, the model needs to be refined further. The question why the two sensors differ is discussed but the true origin of the cause remains unsolved. The conclusion is that the error can be drastically reduced with just an offset. It is also shown that when building a lambda sensing device the controller is of equal importance as the sensor element itself. This is due to the sensitivity of surrounding factors that the controller must be able to handle. These effects are specially important for engines running at lambda not equal to 1, for example diesel engines.