The small carrier wavelength at millimeter-wave (mm-Wave) frequencies allows the possibility of implementing a large number of antennas on a single chip. This work uses the potential of large antenna arrays at these frequencies to develop a low-complexity directional modulation technique: Antenna Subset Modulation (ASM) for point-to-point secure wireless communication. The main idea in ASM is to communicate information by modulating the far-field radiation pattern of the array at the symbol rate. By driving only a subset of antennas and changing the subset used for each symbol transmission the far-field pattern is modulated. Two techniques for implementing antenna subset selection are proposed. The first technique is simple where the antenna subset to be used is selected at random for every symbol transmission. While randomly switching antenna subsets does not affect the symbol modulation for a desired receiver along the main lobe direction, it effectively randomizes the amplitude and phase of the received symbol for an eavesdropper along a sidelobe. Using a simplified statistical model for random antenna subset selection, an expression for the average symbol error rate (SER) is derived as a function of observation angle for linear arrays. To overcome the problem of large peak sidelobe level in random antenna subset switching, an optimized antenna subset selection procedure based on simulated annealing is then discussed. Finally, numerical results comparing the average SER performance of the proposed techniques against conventional array transmission are presented. While both methods produce a narrower information beam-width in the desired direction, the optimized antenna subset selection technique is shown to offer better security and array performance. / text

Millimeter-wave (mmWave) communications is a promising enabling technology for high rate (Giga-bit) multimedia applications. However, because oxygen absorption peaks at 60 GHz, mmWave signal power degrades significantly over long distances. Therefore, a traffic flow transmitting over multiple short hops is preferred to improve the flow throughput. In this thesis, we first design a hop selection metric for the piconet controller (PNC) to select appropriate relay hops for a traffic flow, aiming to improve the flow throughput and balance the traffic loads across the network. We then propose a multi-hop concurrent transmission (MHCT) scheme to exploit the spatial diversity of the mmWave WPAN by allowing multiple communication links to transmit simultaneously. By deriving the probability that two links can transmit simultaneously as a function of link length, the MHCT scheme is capable of improving spatial multiplexing gain in comparison with the single hop concurrent transmission (SHCT) scheme. We theoretically demonstrate that by properly breaking a single long hop into multiple short hops, the time resource can be utilized more efficiently, thus supporting more traffic flows in the network within the same time interval. In addition, the per-flow throughput is obtained analytically. Extensive simulations are conducted to validate the analysis and demonstrate that the proposed MHCT scheme can significantly improve the average traffic flow throughput.

Photonic generation of ultra-low phase noise and frequency-tunable microwave or millimeter-wave (mm-wave) signals has been a topic of interest in the last few years. Advanced photonic techniques, especially the recent advancement in photonic components, have enabled the generation of microwave and mm-wave signals at high frequencies with a large tunable range and ultra-low phase noise. In this thesis, techniques to generate microwave and mm-wave signals in the optical domain are investigated, with an emphasis on system architectures to achieve large frequency tunability and low phase noise. The thesis consists of two parts. In the first part, techniques to generate microwave and mm-wave signals based on microwave frequency multiplication are investigated. Microwave frequency multiplication can be realized in the optical domain based on external modulation using a Mach-Zehnder modulator (MZM), but with limited multiplication factor. Microwave frequency multiplication based on external modulation using two cascaded MZMs to provide a larger multiplication factor has been proposed, but no generalized approach has been developed. In this thesis, a generalized approach to achieving microwave frequency multiplication using two cascaded MZMs is presented. A theoretical analysis leading to the operating conditions to achieve frequency quadrupling, sextupling or octupling is developed. The system performance in terms of phase noise, tunability and stability is investigated. To achieve microwave generation with a frequency multiplication factor (FMF) of 12, a technique based on a joint operation of polarization modulation, four-wave mixing and stimulated-Brillouin-scattering-assisted filtering is also proposed. The generation of a frequency-tunable mm-wave signal from 48 to 132 GHz is demonstrated. The proposed architecture can even potentially boost the FMF up to 24. In the second part, techniques to generate ultra-low phase noise and frequency-tunable microwave and mm-wave signals based on an optoelectronic oscillator (OEO) are studied. The key component in an OEO to achieve low phase noise and large frequency-tunable operation is the microwave bandpass filter. In the thesis, we first develop a microwave photonic filter with an ultra-narrow passband and large tunability based on a phase-shifted fiber Bragg grating (PS-FBG). Then, an OEO incorporating such a microwave photonic filter is developed. The performance including the tunable range and phase noise is evaluated. To further increase the frequency tunable range, a technique to achieve microwave frequency multiplication in an OEO is proposed. An mm-wave signal with a tunable range more than 40 GHz is demonstrated.

Thesis (M.S.)--University of Delaware, 2008. / Principal faculty advisor: Dennis W. Prather, Dept. of Electrical & Computer Engineering. Includes bibliographical references.

Terahertz source technology has been an active area of research for a number of years. This has helped develop continuous wave solid-state sources that are highly desirable in a wide range of applications spanning from Earth science to medical science. However, even with advances in terahertz technology, the generation of fundamental source power at these frequencies is still challenging. Promising electronic solid-state devices fall short in overcoming source power shortage due to electronic breakdown mechanism and fabrication limits at terahertz frequencies. The fundamental physical limitation of photonic devices, such as low photon energy, force cryogenic operation which at times is impractical. Schottky diode frequency multipliers often offer a very practical solution for generating continuous wave radiation based on solid-state technology. This harmonic source technology is today a most certain candidate for many applications where compactness and room temperature operation is desired. However, despite of all the advances in Schottky diode fabrication and their use in frequency multiplication, output power falls rapidly with increasing frequency. Thermal constrains, fabrication limits, assembly errors and parasitic losses all constitute changes that affect the performance of these devices and make it difficult to reproduce experimental data. To overcome these problems and progress towards the generation of milliwatts of power at terahertz frequencies, the study of existing methods to generate and handle high power is necessary. In the first part of the thesis, the design, fabrication and development of two Schottky diode-based frequency doublers is discussed. The work focuses on the generation of high-power sources that are capable of handling higher input powers while maintaining good thermal efficiencies. A detailed study into the machining tolerances, assembly errors and temperature effects are evaluated for the frequency doublers. High frequency effect such as velocity saturation is also addressed. Depending on the design frequency and power handling, two different circuit configurations are employed for the frequency doublers. While the high-power 80/160 GHz frequency doubler used a discrete flip-chip diode configuration, the 160/320 GHz frequency doubler employed an integrated diode membrane to mitigate sensitivity issues encountered during assembly and enable correlation between simulated and measured data. The second part proposes the use of millimeter-wave Schottky diode-based radiometers for imaging of composites samples. The focus of this experiment is the introduction of an alternate EM inspection method with the use of broadband Schottky diode components. This technique combines two different fields {--} non-destructive testing and radiometry, which presents a potentially new and interesting area for research. Since no single method can qualify to be the most accurate for all inspections, and with the future integration bringing down manufacturing costs of high frequency components, this demonstration presents a new approach to consider for future material imaging and evaluation experiments.

Photonic generation of ultra-low phase noise and frequency-tunable microwave or millimeter-wave (mm-wave) signals has been a topic of interest in the last few years. Advanced photonic techniques, especially the recent advancement in photonic components, have enabled the generation of microwave and mm-wave signals at high frequencies with a large tunable range and ultra-low phase noise. In this thesis, techniques to generate microwave and mm-wave signals in the optical domain are investigated, with an emphasis on system architectures to achieve large frequency tunability and low phase noise. The thesis consists of two parts. In the first part, techniques to generate microwave and mm-wave signals based on microwave frequency multiplication are investigated. Microwave frequency multiplication can be realized in the optical domain based on external modulation using a Mach-Zehnder modulator (MZM), but with limited multiplication factor. Microwave frequency multiplication based on external modulation using two cascaded MZMs to provide a larger multiplication factor has been proposed, but no generalized approach has been developed. In this thesis, a generalized approach to achieving microwave frequency multiplication using two cascaded MZMs is presented. A theoretical analysis leading to the operating conditions to achieve frequency quadrupling, sextupling or octupling is developed. The system performance in terms of phase noise, tunability and stability is investigated. To achieve microwave generation with a frequency multiplication factor (FMF) of 12, a technique based on a joint operation of polarization modulation, four-wave mixing and stimulated-Brillouin-scattering-assisted filtering is also proposed. The generation of a frequency-tunable mm-wave signal from 48 to 132 GHz is demonstrated. The proposed architecture can even potentially boost the FMF up to 24. In the second part, techniques to generate ultra-low phase noise and frequency-tunable microwave and mm-wave signals based on an optoelectronic oscillator (OEO) are studied. The key component in an OEO to achieve low phase noise and large frequency-tunable operation is the microwave bandpass filter. In the thesis, we first develop a microwave photonic filter with an ultra-narrow passband and large tunability based on a phase-shifted fiber Bragg grating (PS-FBG). Then, an OEO incorporating such a microwave photonic filter is developed. The performance including the tunable range and phase noise is evaluated. To further increase the frequency tunable range, a technique to achieve microwave frequency multiplication in an OEO is proposed. An mm-wave signal with a tunable range more than 40 GHz is demonstrated.

Astronomical instruments dedicated to the study of Cosmic Microwave Background polarization are in need of optics with very low systematic effects such as beam shape and cross-polarization in an optical configuration. With the demand for millimetre wave larger focal planes comprising thousands of pixels, these systematic effects have to be minimal across the whole focal surface. In order to reach the instrument requirements such as resolution, cross-polarization and beam ellipticity, new optical configurations with well-understood components have to be studied. Refractive configurations are of great importance amongst the potential candidates. The aim is to bring the required technology to the same level of maturity that has been achieved with well-understood existing ones. This thesis is focused on the study of such optical components for the W-band spectral domain. Using optical modelling with various software packages, combined with the manufacture and accurate experimental characterization of some prototype components, a better understanding of their performance has been reached. To do so, several test set-ups have been developed. Thanks to these new results, full Radio-Frequency refractive systems can be more reliably conceived.

Bandpass filters are an essential component of wireless communication systems that only transmits frequencies corresponding to the communication band and rejects all other frequencies. As the deployment of 5G draws nearer, first deployments are expected in 2020 [1], the need for viable filters at the new frequency bands becomes more imminent. Size and performance are two critical considerations for a filter that will be used in emerging mobile communication applications. The high frequency of 5G communication, 28 GHz as opposed to sub 6 GHz for nearly all previous communication protocols, means that previously utilized lumped component based solutions cannot be implemented since they are ill-suited for mm-wave applications. The focus of this work is the miniaturization of a high-performance filter. The Substrate Integrated Waveguide (SIW) is a high performance and promising structure and Low Temperature Co-Fired Ceramic (LTCC) is a high-performance material that both can operate at higher frequencies than the technologies used for previous telecommunication generations. To miniaturize the structure, a compact folded four-cavity SIW filter is designed, implemented and tested. The feeding structure is integrated into the filter to exploit the System on Package (SoP) attributes of LTCC and further reduce the total area of the filter individually and holistically when looking at the final integrated system. Two unique three dimensional (3D) integrated SoP LTCC two-stage SIW single cavity filters and one unique four-cavity filter all with embedded planar resonators are designed, fabricated and tested. The embedded resonators create a two-stage effect in a single cavity filter. The better single cavity design provides a 15% fractional bandwidth at a center frequency of 28.12 GHz, and with an insertion loss of -0.53 dB. The fabricated four-cavity filter has a 3-dB bandwidth of .98GHz centered at 27.465 GHz, and with an insertion loss of -2.66 dB. The designs presented highlight some of the previously leveraged advantages of SoP designs while also including additions of embedded planar resonators to feed the SIW cavity. The integration of both elements realizes a compact and high-performance filter that is well suited for future mm-wave applications including 5G.

The millimeter wave (mmW) band, commonly referred to as the frequency band between 30 GHz and 300 GHz, is seen as a possible candidate to increase achievable rates for mobile applications due to the existence of free spectrum. However, the high path loss necessitates the use of highly directional antennas. Furthermore, impairments and power constraints make it difficult to provide full digital beamforming systems. In this thesis, we approach this problem by proposing effective beam alignment and beam tracking algorithms for low-complex analog beamforming (ABF) systems, showing their applicability by experimental demonstration. After taking a closer look at particular features of the mmW channel properties and introducing the beamforming as a spatial filter, we begin our investigations with the application of detection theory for the non-convex beam alignment problem. Based on an M-ary hypothesis test, we derive algorithms for defining the length of the training signal efficiently. Using the concept of black-box optimization algorithms, which allow optimization of non-convex algorithms, we propose a beam alignment algorithm for codebook-based ABF based systems, which is shown to reduce the training overhead significantly. As a low-complex alternative, we propose a two-staged gradient-based beam alignment algorithm that uses convex optimization strategies after finding a subregion of the beam alignment function in which the function can be regarded convex. This algorithm is implemented in a real-time prototype system and shows its superiority over the exhaustive search approach in simulations and experiments. Finally, we propose a beam tracking algorithm for supporting mobility. Experiments and comparisons with a ray-tracing channel model show that it can be used efficiently in line of sight (LoS) and non line of sight (NLoS) scenarios for walking-speed movements.

Background: Evaluation of Data Visualization methods is a major challenge within the software and other industries. With complex data and requirements, often organizations require effective visualization methods which impact business decisions and convince stakeholders. This is a similar challenge in the development of a software demonstrator for the innovative safety radar system at ABB Jokab Safety whose aim is to improve the detection reliability using multiple radar sensors and requires an effective visualization method which will satisfy all the requirements. Objectives: The main objective of this study is to explore different data visualization methods involved in illustrating the raw data and with the help of developers, and other team members feedback with reference to existing literature and filter them with respect to the system functionalities. Establish evaluation criteria with relevant metrics to perform analytic evaluations on the visualization methods to determine an effective method. Methods: A Case Study which includes a multivocal literature review, is conducted at ABB Jokab Safety. Initially, to gather information on the subject, both formal and grey literature are explored and documented to filter our appropriate data visualization methods for this system. A task-based evaluation using semi-structured interview is conducted on 14 participants to determine an effective visualization method followed by statistical analysis to derive proper validation of the findings. The Response time, Ease of understanding, Confidence and Accuracy of the visualization methods are evaluated with feedback from the participants. Results: The Multivocal literature review filtered 16 primary articles which encouraged the use of 4 data visualization methods used in the safety radar system with distinct functionalities. A coordinate transformation engine to combine the data sets was also developed for the safety radar system contributing to the overall improvement of detection reliability. The evaluation including both quantitative and qualitative results validate each other’s findings through statistical tests like Kruskal-Wallis and Bonferroni post hoc followed by narrative analysis resulting a heat temperature plot to be more effective in the visualization of the radar data from multiple sensors. Conclusions: The results from this research provide insight into how data visualization evaluation can be implemented for real-time industrial problems and furnish validation process to determine an effective data visualization method. This study helps object detection using similar radar technologies visualize their data in an effective way and provides a scientific approach for evaluating similar data visualization problems.