Ad hoc networks provide a flexible, infrastructure-free means to communicate between soldiers in war zones, aid workers in disaster areas, or consumers in device-to-device (D2D) applications. Ad hoc networks, however, are stilled plagued by interference. Communication with millimeter-wave (mmWave) devices offers hope to ad hoc networks through higher bandwidth, reduced interference due to directional antennas, and a lighter interference field due to blockage. This report uses a stochastic geometry approach to characterize the one-way and two-way coverage probability of a mmWave ad hoc network with directional antennas and random blockages. The coverage probability in the presence of noise and both line-of-sight and non-line-of-sight interference is analyzed and used to derive the transmission capacity. Several reasonable simplifications are used to derive the transmission capacity. Performance of mmWave is then analyzed in terms of area spectral efficiency and rate coverage. The results show that mmWave networks support larger densities, higher area spectral efficiencies, and better rate coverage compared to microwave ad hoc networks. / text

This dissertation presents new circuit architectures and techniques for improving the performance of several key BiCMOS RFIC building blocks used in radar and wireless communication systems operating up to millimeter-wave frequencies, and the development of an advanced, low-cost and miniature millimeter-wave concurrent dual-band transmitter for short-range, high-resolution radar and high-rate communication systems. A new type of low-power active balun consisting of a common emitter amplifier with degenerative inductor and a common collector amplifier is proposed. The parasitic neutralization and compensation techniques are used to keep the balun well balanced at very high frequencies and across an ultra-wide bandwidth. A novel RF switch architecture with ultra-high isolation and possible gain is proposed, analyzed and demonstrated. The new RF switch architecture achieves an ultra-high isolation through implementation of a new RF leaking cancellation technique. A new class of concurrent dual-band impedance matching networks and technique for synthesizing them are presented together with a 25.5/37-GHz concurrent dual-band PA. These matching networks enable simultaneous matching of two arbitrary loads to two arbitrary sources at two different frequencies, utilizing the impedance-equivalence properties of LC networks that any LC network can be equivalent to an inductor, capacitor, open or short at different frequencies. K- and Ka-band ultra-low-leakage RF-pulse formers capable of producing very narrow RF pulses in the order of 200 ps with small rising and falling time for short-range high-resolution radar and high-data-rate communication systems are also developed. The complete transmitter exhibiting unique characteristics obtained from capabilities of producing very narrow and tunable RF pulses with extremely RF leakage and working concurrently in dual bands at 24.5 and 35 GHz was designed. Capability of generating narrow and tunable RF pulses allows the radar system to flexibly work at high and multiple range resolutions. The extremely low RF leakage allows the transmitter to share one antenna system with receiver, turn on the PA at all time, comply the transmitting spectrum requirements, increase the system dynamic range, avoid harming to other systems; hence improving system size, cost and performance. High data-rate in communication systems is achieved as the consequence of transmitting very narrow RF pulses at high rates. In addition, the dissertation demonstrates a design approach for low chip-area, cost and power consumption systems in which a single dual-band component (power amplifier) is designed to operate with two RF signals simultaneously.

Broadband voltage-controlled oscillators are critical to the design of millimeter wave frequency synthesizers. This thesis proposes a design technique that can be used to significantly extend the achievable frequency span of an oscillator. A dual-band oscillator topology is described that can be configured to operate in one of two modes, by an electrical reconfiguration of the negative resistance core around the resonant tank, without switching passive elements within the tank itself. The configuration helps to minimize the difference in phase noise performance between the two modes, while achieving a wide tuning range. To verify the concept, a mm-wave VCO that operates at 30-GHz is designed in a commercial 0.18-um CMOS technology, with an approximate simulated tuning range of 20%. A dual-mode oscillator is also designed in a 0.13-um technology at 60-GHz. / text

No description available.

This thesis investigates the integration of planar antennas, such as Dielectric Resonator Antennas (DRAs) to the planar waveguide structure, specifically the Substrate Integrated Waveguide (SIW) for high radiation efficiency millimeter-wave (mm-wave) applications. The SIW is a low cost and low loss technology, since it almost keeps the guided wave inside the structure. Therefore, it is an excellent candidate feeding scheme compared to traditional planar (multi-conductor) structures, such as the Microstrip Line (MSL) and Co-planar Waveguide (CPW) for many planar antennas. It enhances the antenna???s overall radiation efficiency by minimizing the conduction loss, which dominates at the mm-wave frequency band. For this thesis, two different SIW-integrated DRA configurations operating at mm-wave frequency band are presented. The rectangular DRA is excited in its fundamental mode TE??11 for radiation through a narrow slot cut on the SIW broad wall. However, the coupling slot itself is excited by the SIW TE10 fundamental mode. In addition, the design guidelines, and a parametric study is also conducted on the proposed antenna parameters to investigate their impact on the antenna???s overall performance including the reflection coefficient and radiation pattern (gain). The results are provided within this thesis. The antenna is made of low cost and low loss materials that are available commercially. It is fabricated by using a novel and simple technique, which is compatible with the Printed Circuit Board (PCB) technology. The board is treated as multi-layers composed of the SIW-layer, and DRA element(s) layer, respectively. The fabricated antenna prototypes are tested to demonstrate their validity for real microwave/mm-wave applications. Their reflection coefficients and radiation patterns are measured, and the antenna shows a boresight gain of 5.51 dB and a radiation efficiency of more than 90 % over the operating frequency band of 33-40 GHz. Antenna arrays based on the SIW integrated DRA are investigated for high gain/radiation efficiency applications. Different array configurations such as, linear (series-fed and corporate-fed) and two-dimensional (2D) arrays are presented. The series-fed DRA array is characterized by a single SIW line loaded by DRA-slot pairs, whereas the SIW-power splitter is used to form the corporate-fed DRA array, when loaded by DRA-slot pairs. While the SIW hybrid-feeding scheme (series-feed combined with corporate-feed) is used to form 2D DRA arrays. In this design, the SIW-power splitter is used to split the power equally and in-phase among the sets (rows) of SIW series fed-DRA elements (columns). A simple and generic Transmission Line (T.L.) circuit model is proposed to simplify and expedite the antenna array design process. It is used to calculate the antenna reflection coefficient and radiation pattern (gain). The T.L. model does not take the mutual coupling between the DRA elements into account, since our study shows that its less than -20 dB over the operating bandwidth. However, it is useful and faster than full-wave solvers, such as HFSS, which consumes time and memory due to the huge generated mesh. The developed T.L. circuit model is used to design the antenna array and study the impact of its main designed parameters on the antenna performance. The developed antenna array T.L. model leads to a general design methodology (guidelines). It also allows for optimum array designs for a given set of performance requirements and to have more physical insight into the SIW technology based antenna systems for mm-wave bands. The designed antenna array samples are fabricated and tested within the operating frequency band 33-40 GHz. The series-fed antenna array shows a measured boresight gain of 11.70 dB, and high radiation efficiency, which is more than 90 % over an operating frequency band of 4%. Furthermore, the measured results are compared to these calculated by the proposed T.L. circuit model and full-wave solver. A good agreement between the measured and the HFSS results are observed, especially near the frequency at which the reflection coefficient is minimum. However, some deviation is noticed between the proposed circuit model and the measured results. This deviation is attributed to the discrete nature of the SIW structure that affects the Short Circuit (SC) performance (magnitude and phase), the T.L. lengths, and the mutual coupling between any two adjacent antenna elements. All these issues are handled efficiently and are taken into account by the full-wave solver. Therefore, the measured reflection coefficient agrees with that of the HFSS, except for a very small deviation, caused by the fabrication tolerances and measurement errors. However, the proposed T.L. circuit model is still valid and can easily predict and estimate the resonance behavior and the impedance bandwidth of the proposed antenna arrays in a very short time compared with the full-wave solver.

Thesis (M.S.E.C.E.)--University of Delaware, 2008. / Principal faculty advisor: . Includes bibliographical references.

Thesis (M.S.E.C.E.)--University of Massachusetts Amherst, 2008. / Includes bibliographical references (p. 117-119).

Thesis (Ph. D.)--University of Massachusetts Amherst, 2009. / Open access. Includes bibliographical references (p. 179-184). Print copy also available.

The energy and data rate requirements for the next generation cellular networks urge the need for innovative solutions. Inspired by its massive bandwidth, millimeter wave (mmWave) band is thought-out to be one of the key elements to meet the aspirations. However, mmWave links are known to have short coverage distance due to the propagation losses introduced at high frequencies. The proposed solutions to overcome the transmission challenges include using large arrays with improved directivity, adopting smaller cells, and relying on cooperative networks to extend the mmWave link and avoid shadowing areas. This work aims to improve the connectivity of the mmWave link in the outdoor environments. One of the cost effective methods is to increase the array gain by using Analogue Beamforming (ABF). The performance of the ABF system in the presence of phase quantization error has been analytically investigated. The study also includes comparing three different channel sounding techniques, namely: exhaustive search, side-to-side search, and n-tier search. The time overhead related to each method and their energy consumption are calculated. The numerical results assist in determining the optimum search period to obtain a reasonable spectral efficiency using minimal power consumption. The results also help identify the minimum number of quantization bits required to produce about ninety percent of the optimistic results. In order to extend the coverage further, relay networks are considered an essential component in mmWave communications. The performance of a single hybrid beamforming full-duplex relay system and multi-relay networks were investigated. The design algorithms for the processors in the network are proposed based on the greedy pursuit approach. The performance of the proposed algorithms is analysed under various scenarios. The analysis highlights the influence of the array size, the number of RF chains, and the length of the channel sounding period. The performance of the proposed systems is compared from both the spectral efficiency and power consumption prospects. The results also establish that the number of antennas at the source and the relay receiver arrays have a superior impact on the system performance than the sizes of the array at the destination and the relay transmitter.

<p>Millimeter-wave communications use narrow beams to overcome the enormous signal attenuation. Such narrow-beam communication demands precise beam-alignment between transmitter and receiver and may entail huge overhead, especially in high mobility scenarios. Moreover, detection of the optimal beam is challenging in the presence of beam imperfections and system noise. This thesis addresses the challenges in the design of beam-training and data-communication by proposing various schemes that exploit different timescales. On a short timescale, we leverage the feedback from the receiver to efficiently perform beam-training and data-communication. To this end, we have worked in three different areas. In the first research direction, we design an optimal interactive beam-training and data-communication protocol, with the goal of minimizing power consumption under a minimum rate constraint. The optimality of a fixed-length beam-training phase followed by a data-communication phase is proved under the assumption of perfect binary feedback. In the second research direction, we propose a coded energy-efficient beam-training scheme, robust against the feedback/detection errors. In the third research direction, we investigate the design of the beam-training in the presence of uncertainty due to noise and beam imperfections. Based on the bounding of value-function, the second-best preference policy is proposed, which achieves a promising exploration-exploitation tradeoff. On the other hand, on longer timescales, we exploit the mobility and blockage dynamics and beam-training feedback to design throughput-efficient beam-training and data-communication. We propose a point-based value iteration (PBVI) algorithm to determine an approximately optimal policy. However, the design relies on the a-priori knowledge of the state dynamics, which may not be available in practice. To address this, we propose a dual timescale approach, where on the long timescale, a recurrent deep variational autoencoder (R-VAE) uses noisy beam-training observations to learna probabilistic model of system dynamics; on the short timescale, an adaptive beam-training procedure is optimized using PBVI based on beam-training feedback and a probabilistic knowledge of the UE's position provided by the R-VAE. In turn, the observations collected during the beam-training procedure are used to refine the R-VAE via stochastic gradient descent in a continuous process of learning and adaptation.<br></p>