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<p> The allocation of 7.5 GHz of bandwidth by the Federal Communication Commission (FCC) for ultra-wideband (UWB) applications has provided an exciting and a challenging opportunity to design short range wireless communication and microwave imaging systems. To fully realize the potential of the UWB, communication and microwave imaging systems are required to operate over the entire UWB frequency band. The combination of the wide bandwidth requirement and the target application of the UWB systems have led to a surge of interest in designing of novel integrated circuits and antennas for the UWB applications. In any wireless communication and microwave imaging system, the antenna has a fundamental effect on the overall performance of the system, and as a result, it has attracted considerable research interest.</p> <p> This thesis focuses on the design of UWB antennas that are suitable for UWB cancer detection and wireless communication systems. Two planar antennas, one a printed monopole antenna, and the other, a printed slot antenna fed with a coplanar waveguide, are presented in this work. First, the antennas have been designed to operate in air, making them suitable for the UWB wireless short range communication applications. Measurement and simulation results indicate that both antennas achieve input impedance matching in a bandwidth of more than 7.5 GHz. The effect on the input matching of the antennas due to the variation in their geometrical parameters has been studied and both antennas have been fully characterized in air. Next, the two antennas have been redesigned to operate in a coupling medium for medical imaging applications. Both antennas achieve return loss of less than -10 dB over the entire UWB spectrum. Also, the antennas have been fully characterized while operating in the coupling medium and in proximity to a human body model. Finally, a two-element antenna array, based on the printed monopole antenna and the printed slot antenna, in co- and cross-polarized array formation, has been designed. The tumor detection capabilities of all antenna arrays for different scenarios have been studied through electromagnetic simulation and measurements.</p> / Thesis / Master of Applied Science (MASc)

<p> As modern digital communications evolve, the requirements imposed on the systems than are required to transmit/receive the signals involved become more stringent. Amplifiers are required to provide gain from low frequencies, sometimes down to DC, up to high frequencies in the order of few to tens of gigahertz. Not only is the gainbandwidth product to be enhanced, but also the amplifier should introduce minimal distortion to the signal and consume as low power as possible. </p> <p> Distributed amplification is a multi-stage broadband circuit technique that may provide such a function. In distributed amplifiers, inter-stage transmission lines provide the capability to reach higher operational frequencies by absorbing the parasitic capacitances of the transistors used. Unlike other broadband topologies that trade-off gain and bandwidth, distributed amplifiers do not, but rather, the trade-off is between gain and delay. As gain stages are added, the gain increases as the bandwidth remains the same but the signal delay is increased. </p> <p> This work considers the silicon germanium (SiGe) heterojunction bipolar transistor (HBT) implementation of distributed amplifiers. SiGe HBTs incorporate a thin SiGe base with Ge profiling to achieve high cut-off frequencies. SiGe BiCMOS processes are silicon based and hence have the major advantage of integrability to the low cost CMOS process unlike ill-V compound semiconductors. Hence, SiGe is a promising technology capable of bridging the performance gap between silicon and m-v semiconductors. </p> <p> The proposed amplifier achieves an approximately flat gain of 6.5 dB and a noise figure of 5.8-9 dB throughout the -3 dB passband of 10.5 GHz. The power consumed is 12.2 mW, significantly lower than previously published results by up to an order of magnitude is some cases. The group delay of the amplifier was found to be approximately constant in the passband at -60 ps. </p> <p> For the first time, temperature measurements are preformed on SiGe HBT DAs. Analysis show that the gain falls drastically with temperature increase due to deterioration in input matching caused by the significant change in the transistors input impedance with temperature. Similarly the NF, increases with temperature due to the decrease in gain. Moreover, noise analysis of SiGe HBT DAs is investigated, producing simulations predicting the NF of the proposed amplifier giving insight as to how noise may be reduced in future designs. </p> / Thesis / Master of Applied Science (MASc)

Yes / This study presents a wideband multiple-input-multiple-output (MIMO) antenna for Wifi/WLAN/LTE applications. The antenna consists of two triangular patches as the radiating elements placed orthogonally to each other. Two T-slots and a rectangular slot were etched on the ground plane to improve return loss and isolation. The total dimension of the proposed antenna is 30 x 30 mm2. The antenna yields impedance bandwidth of 101.7% between 2.28 GHz up to 7 GHz with a reflection coefficient of < -10 dB, and mutual coupling of < -14 dB. The results including S-Parameters, MIMO characteristics with analysis of envelope correlation coefficient (ECC), total active reflection coefficient (TARC), capacity loss, channel capacity, VSWR, antenna gain and radiation patterns are evaluated. These characteristics indicate that the proposed antenna is suitable for MIMO wireless applications.

Yes / A compact dielectric resonator antenna (DRA) for wideband applications is proposed. Two cylindrical dielectric resonators which are asymmetrically located with respect to the center of a rectangular coupling aperture are fed through this aperture. By optimizing the design parameters, an impedance bandwidth of about 29%, covering the frequency range from 9.62 GHz to 12.9 GHz, and a gain of 8 dBi are obtained. Design details of the proposed antenna and the results of both simulation and experiment are presented and discussed.

Ultra-wideband (UWB) communications is expected to revolutionize high data-rate, short-distance wireless communications, providing data-rates in excess of 100 Mbps. However, the wireless channel distorts the transmitted signal by dispersing the signal energy over time. This degrades the output signal-to-noise ratio (SNR) of a correlation based matched-filter receiver, limiting the achievable data-rate and user capacity. Most wideband channel models do not account for all the identified dispersion mechanisms namely the frequency dispersion, the resonant dispersion and the multipath dispersion. The objective of this research is to model resonant dispersion based on the Singularity Expansion Method (SEM) and provide guidelines for UWB receiver design to meet the data capacity. The original contribution of this research is a novel pole dispersion channel model that includes resonant dispersion characterization. An empirical investigation supports our claim that a correlation type matched-filter receiver using a template signal based on the pole dispersion channel model overcomes distortion related losses. Various physical mechanisms responsible for dispersion in UWB communication systems are described in detail. The applicability of the proposed dispersive channel model is evaluated using the optimal matched filter (OMF) receiver. The SEM approach, which was originally proposed for target identification using short pulse radars, offers limited benefits of due to its susceptibility to noise. A combined fuzzy-statistical approach is proposed to improve the robustness of resonant dispersion channel modeling in presence of noise. A natural extension of this doctoral research is to improve buried landmine detection as well as breast tumor detection by applying statistical and fuzzy analysis to the backscatter response. Moreover, radar target identification using UWB short pulses stands to gain tremendously from this research. / Ph. D.

Recent technologies enable wireless communication devices to become physically smaller in size. Antenna size is obviously a major factor that limits miniaturization. In the past few years, new designs of low-profile antennas for handheld wireless devices have been developed. The major drawback of many low-profile antenna designs is their narrow impedance bandwidth. Furthermore, the market trend of personal wireless devices is moving toward a universal system that can be used anywhere and rapid expansion of the wireless communication industry has created a need for connectivity among various wireless devices using short-range wireless links in the Bluetooth operating band to get rid of the cable connections. This requires therefore multiple frequency band operation. In summary, physically small size, wide bandwidth, and high efficiency are the desired characteristics of antennas in mobile systems. This dissertation presents a comprehensive analysis of a new wide-bandwidth compact antenna, called WC J-pole antenna, covering 50 % impedance fractional bandwidth. A set of guidelines is also provided for a bandwidth-optimized design at any frequency. A few design variations of the proposed antenna are also presented for existing commercial wireless applications. Efficiency is perhaps the most important characteristic of small antennas for mobile systems. An extension of the Wheeler cap method to moderate-length and wideband antennas is developed to measure quickly efficiency. The dissertation also provides a review of human operator interaction with handset antennas. Since the proposed antenna is intended to be used in the proximity of human body and in a casing, coupling effects of human body and casing on the antenna characteristics and radio frequency (RF) energy absorption into the human body are investigated. / Ph. D.

Dynamic spectrum sharing (DSS) is a new paradigm for spectrum allocation that is expected to lead to more efficient spectrum usage and alleviate the spectrum-scarcity that has been perceived in recent years. DSS refers to the opportunistic, dynamic, and uncoordinated use of the spectrum by multiple, possibly non-cooperating, systems. It allows bands which may be underutilized by incumbent or legacy systems to be shared by agile or cognitive radios on a ``do no harm" basis. An ideal DSS technique is one which efficiently uses the allocated spectrum and maximizes the performance of the DSS network while causing no interference to the legacy radio system with which it coexists. We address this issue in our work by investigating desirable features for DSS with respect to the impact on a legacy radio system as well as the performance of a DSS network. It is found that ``ideal" DSS techniques with respect to both objectives are characterized by the removal of the strongest interferers in the system and averaging of the remaining interference. This motivates the use of an interference avoidance (IA) based underlay technique for DSS. The performance benefit provided by this technique, over an IA-based overlay technique, is shown to increase with the transmission bandwidth available to the DSS system. It is also shown that this technique is more robust to inaccuracies in the system knowledge required for implementing IA. An example of an IA-based underlay technique is a spreading-sequence-based transmission scheme that employs sequence adaptation to avoid interference. We use game-theoretic tools to design such schemes for distributed or ad hoc networks. The designed schemes can also be used to avoid interfering with other agile or static radios. We then extend this work to Ultra Wideband systems which can maximally exploit the gains from the proposed scheme due to the large transmission bandwidths. / Ph. D.