This dissertation introduces new and simple techniques for suppression of multispurious passbands, which are inherent to the conventional microstrip parallel coupleline bandpass filters. In addition, the operation of harmonic suppression is analyzed using a simple model. Special emphasis is placed on the applications of several new filter designs for microstrip diplexers and multiplexers. Compact, full-duplex beam scanning antenna transceiver systems with extremely broad bandwidth have also been developed. Recent advances in broadband monolithic microwave integrated circuit (MMIC) amplifiers make the realization of extremely broadband phased-array transceiver systems possible. The ultra-wideband phased-array transceiver systems can be used in multi-band mobile satellite communication systems and wideband radars. This dissertation presents a multi-band, compact, full-duplex, beam scanning antenna transceiver system for satellite communications and two designs of ultra-wideband, low-cost radar systems as applications of the MMIC amplifiers. In addition, a multi-frequency antenna has been developed. A single-feed triple frequency microstrip patch antenna is presented as an answer to the recent demand for multi-function systems in the wireless communications. In summary, the research presented in this dissertation covers every component required to build an ultra-wideband, full-duplex beam scanning phased-array antenna transceiver. The work done in this dissertation should have many applications in the wireless communication systems and wideband radar technologies.

ITC/USA 2014 Conference Proceedings / The Fiftieth Annual International Telemetering Conference and Technical Exhibition / October 20-23, 2014 / Town and Country Resort & Convention Center, San Diego, CA / This paper addresses the future military munitions' system requirements for antennas in terms of the existing versus new fabrication technology. The antenna requirements of the future smart munitions will be GPS for precision guidance and TM for system performance testing. The environmental requirements remain the same; large temperature operating range with operation at high temperatures and high shock capable. As usual, the munitions are getting smaller, frequency bandwidth is getting larger, and the cost of the antennas must be minimized in production quantities. In particular this paper compares the existing antenna fabrication technology of Teflon based dielectric printed circuits versus multilayer alumina in the green state, a technology that has been perfected for fabricating microwave integrated circuits (MIC's). The trade-offs that will be addressed are temperature, shock, cost, tunability, loss, size, dielectric constant, and frequency bandwidth. There has been a significant effort to miniaturize the GPS and TM antenna using higher dielectric constant materials. The most popular direction of this effort has been to use ceramic impregnated Teflon. The ultimate temperature performance is the material with a dielectric constant around 2 since this material exhibits a very low coefficient of change with temperature. Materials are available with nominal dielectric constants of 6 and 10 to reduce the size of the antenna but the coefficient of change with temperature is very large and leaves these materials marginal for military temperature ranges. There have also been two other problems with Teflon based printed circuit boards, forming and bonding the boards in a 3D shape and homogeneity of the dielectric constant in the board and after bonding. These problems usually make tuning a requirement and drive the cost of antenna fabrication up. There has been a revolution in MIC's. The circuits are now being made with multiple layers of ceramic (alumina) with interlayer conductive connections and a nominal dielectric constant of 10. The layers are formed in the green state and fired at high temperature and the resulting alumina substrate has a very low coefficient of change with temperature and low loss. Since this procedure is now beyond development, the cost is low and the volume capability is high. Another significant point is that the part can be any shape since the substrate is done in the green state (formable) and then fired.

Swath bathymetry sidescan (SBS) sonar and the angle-of-arrival processing that underlies these systems has the capability to produce much higher resolution three dimensional imagery and bathymetry than traditional beamformed approaches. However, the performance of these high resolution systems is limited by signal-to-noise ratio (SNR) and they are also susceptible to multipath interference. This thesis explores two methods for increasing SNR and mitigating multipath interference for SBS systems. The first, binary coded pulse transmission and pulse compression is shown to increase the SNR and in turn provide reduced angle variance in SBS systems. The second, transmit beamforming, and more specifically steering and shading, is shown to increase both acoustic power in the water and directivity of the transmitted acoustic radiation. The transmit beamforming benefits are achieved by making use of the 8-element linear angle-of-arrival array typical in SBS sonars, but previously not utilized for transmit. Both simulations and real world SBS experiments are devised and conducted and it is shown that in practice pulse compression increases the SNR, and that transmit beamforming increases backscatter intensity and reduces the intensity of interfering multipaths. The improvement in achievable SNR and the reduction in multipath interference provided by the contributions in this thesis further strengthens the importance of SBS systems and angle-of-arrival based processing, as an alternative to beamforming, in underwater three dimensional imaging and mapping. / Graduate / 2015-04-15 / 0544 / 0547 / mark.butowski@gmail.com

One of the most challenging issues facing vehicular networks lies in the design of an efficient MAC protocol due to mobile nature of nodes, delay constraints for safety applications and interference. In this thesis, I propose an efficient Multichannel QoS Cognitive MAC (MQOG). MQOG assesses the quality of channel prior to transmission employing dynamic channel allocation and negotiation algorithms to achieve significant increase in channel reliability, throughput and delay constraints while simultaneously addressing Quality of Service. The uniqueness of MQOG lies in making use of the free unlicensed bands. To consider fair effective sharing of resources I propose a Mobility Based Dynamic Transmit Opportunity (MoByToP) while modifying the 802.11e TXOP (Transmit Opportunity). The proposed protocols were implemented in OMNET++ 4.1, and extensive experiments demonstrated a faster and more efficient reception of safety messages compared to existing VANet MAC Protocols. Finally, improvements in delay, packet delivery ratios and throughput were noticed.

Swath bathymetry sidescan (SBS) sonar and the angle-of-arrival processing that underlies these systems has the capability to produce much higher resolution three dimensional imagery and bathymetry than traditional beamformed approaches. However, the performance of these high resolution systems is limited by signal-to-noise ratio (SNR) and they are also susceptible to multipath interference. This thesis explores two methods for increasing SNR and mitigating multipath interference for SBS systems. The first, binary coded pulse transmission and pulse compression is shown to increase the SNR and in turn provide reduced angle variance in SBS systems. The second, transmit beamforming, and more specifically steering and shading, is shown to increase both acoustic power in the water and directivity of the transmitted acoustic radiation. The transmit beamforming benefits are achieved by making use of the 8-element linear angle-of-arrival array typical in SBS sonars, but previously not utilized for transmit. Both simulations and real world SBS experiments are devised and conducted and it is shown that in practice pulse compression increases the SNR, and that transmit beamforming increases backscatter intensity and reduces the intensity of interfering multipaths. The improvement in achievable SNR and the reduction in multipath interference provided by the contributions in this thesis further strengthens the importance of SBS systems and angle-of-arrival based processing, as an alternative to beamforming, in underwater three dimensional imaging and mapping. / Graduate / 0544 / 0547 / mark.butowski@gmail.com

One of the most challenging issues facing vehicular networks lies in the design of an efficient MAC protocol due to mobile nature of nodes, delay constraints for safety applications and interference. In this thesis, I propose an efficient Multichannel QoS Cognitive MAC (MQOG). MQOG assesses the quality of channel prior to transmission employing dynamic channel allocation and negotiation algorithms to achieve significant increase in channel reliability, throughput and delay constraints while simultaneously addressing Quality of Service. The uniqueness of MQOG lies in making use of the free unlicensed bands. To consider fair effective sharing of resources I propose a Mobility Based Dynamic Transmit Opportunity (MoByToP) while modifying the 802.11e TXOP (Transmit Opportunity). The proposed protocols were implemented in OMNET++ 4.1, and extensive experiments demonstrated a faster and more efficient reception of safety messages compared to existing VANet MAC Protocols. Finally, improvements in delay, packet delivery ratios and throughput were noticed.

<p> The transmit-power control (TPC) problem is a fundamental problem in cognitive radio design, which aims at determining transmit-power levels for secondary users across available subcarriers. This thesis studies both the theory and the algorithms for the TPC problem for cognitive radio networks, and specifically examines the problem under two different limitations: an interference-power limitation and a low-power limitation. First, the TPC problems are cast into game-theoretic models and the sufficient and necessary optimality conditions ·for solutions are derived. Sufficient conditions for the existence, uniqueness and stability of a solution are presented as well. Second, the fast iterative water-filling controller (FIWFC) for the TPC problem is developed, which is linearly convergent under certain conditions. The computational complexity is lower than for the iterative water-filling controller (IWFC) for digital subscriber lines. In order to evaluate the FIWFC, simulations are carried out for both stationary and nonstationary radio environments. In addition, the performance of the FIWFC is evaluated, given the presence of measurement errors. The results of these various simulations show that the FIWFC outperforms IWFC in terms of convergence speed in all cases. </p> / Thesis / Doctor of Philosophy (PhD)

Smart antenna is a potential performance enhancement tool in a communications link that can be used at either end (transmitter or receiver) of the link in the form of beamforming or diversity operation. While receive smart antenna techniques and operations have matured over the years, transmit smart antenna is relatively a new concept that has seen its growth over the past few years. Both these smart antenna operations have been traditionally designed for base station applications. But with the advent of high-speed processors, transmit smart antenna can also be feasible at a small wireless terminal (SWT). This dissertation studied the feasibility of using smart antenna at a SWT. Both smart transmit and receive antennas are studied, including multiple input and multiple output (MIMO) systems, however the emphasis is placed on transmit smart antennas. The study includes algorithm developments and performance evaluations in both flat fading and frequency selective channels. Practical issues, i.e., latency and amount of feedback, related to transmit smart antenna operation are discussed. Various channel measurements are presented to assess the performance of a transmit smart antenna in a real propagation environment. These include vector channel measurements for narrowband and wideband signals, channel reciprocity, and effect of antenna element spacing on diversity performance. Real-time demonstrations of transmit smart antenna have been performed and presented, and, the applicability of the proposed techniques in the Third Generation standards and wireless local area networks (WLAN) is discussed. Receive beamforming with a small number of antenna elements (which is usually the case for a SWT) is analyzed in an interference-limited environment. / Ph. D.

Multiple antennas help in combating the destructive effects of fading as well as improve the spectral efficiency of a communication system. Receive diversity techniques like maximal ratio receive combining have been popular means of introducing multiple antennas into communication systems. Space-time block codes present a way of introducing transmit diversity into the communication system with similar complexity and performance as maximal ratio receive combining. In this thesis we study the performance of space-time block codes in Rayleigh fading channel. In particular, the quasi-static assumption on the fading channel is removed to study how the space-time block coded system behaves in fast fading. In this context, the complexity versus performance trade-off for a space-time block coded receiver is studied. As a means to improve the performance of space-time block coded systems concatenation by convolutional codes is introduced. The improvement in the diversity order by the introduction of convolutional codes into the space-time block coded system is discussed. A general analytic expression for the error performance of a space-time block coded system is derived. This expression is utilized to obtain general expressions for the error performance of convolutionally concatenated space-time block coded systems utilizing both hard and soft decision decoding. Simulation results are presented and are compared with the analytical results. / Master of Science

Magnetic Resonance Imaging (MRI) is considered as a slow imaging technique. Various approaches to accelerate MRI imaging have been explored by researchers in the past decades. Earlier gradient based methods have reached the safety limit. Parallel receiving techniques achieve accelerations by reducing phase encoding steps. Among these methods, SEA Imaging achieved the highest possible acceleration by completely eliminating phase encoding. However, SEA imaging is limited to thin planar slices above the array due to the correction needed for the inherent phase cancellation caused by voxel-sized coils. A phase compensation gradient pulse is used for this correction in SEA imaging. This phase compensation is dependent on slice position and thickness as well as the orientation of the array elements, placing stringent restrictions on SEA imaging, limiting its applications. Converting the SEA system into Transmit / Receive (T/R) mode, which is the main purpose of this study, eliminates the requirement for phase compensation gradient because phase departed during transmit is refocused during receiving. Independent amplitude and phase control of RF pulse for each coil of a SEA array is achieved using a low cost scalable parallel transmit system design. The first 64-channel parallel transmitter for MRI in the world is constructed and tested. Software is also developed to control the phase and amplitude of all the 64 channels of RF excitation pulses independently through National Instruments DAQ system. The system consists of vector modulators controlled by digital controlled potentiometers, two-stage amplifiers and T/R switches on the transmit side. All these are combined with newly designed and constructed preamplifiers and the existing 64-channel parallel receivers on the receive side, leading to the only 64-channel parallel T/R system available for MRI. As a bonus, the system can be easily updated to full Transmit SENSE capability. Furthermore, simulations and images are done to synthesize transmit patterns thanks to the large channel count. Testing results show that the system is capable of 100W per channel simultaneous transmission. Using this system, transmit field can be synthesized by varying the phase and amplitude across channel without traditionally required complicated pulse sequences involving simultaneous RF and gradient fields. Curved slice excitation has conventionally been considered a difficult task for MRI, achievable only through complicated pulses sequences. Using this system and flexible array wrapped around the subject to be imaged, the system is able to excite curved slice using one shot. TR images indicate that the system is capable of high speed surface imaging at 200 frames per second following the surface of a flexible SEA array coil which has not been achieved using other methods in MRI.