1,721,009 research outputs found
Physical optics analysis of electrically small slot-fed substrate lens antennas.
No full textWith the current explosion of microwave wireless communication systems comes the need to produce low cost miniaturized components. Integrated antennas, such as planar microstrip-fed patches and slots, are a promising means of combining the antenna function with the associated transceiver circuitry. However, these antennas suffer from a bi-directional radiation pattern, power loss via substrate modes, a broad radiation pattern, or a combination of the above. To correct these problems, a dielectric lens of hemispherical shape, or slight variation thereof, can be placed directly upon the planar antenna, forming what is called a Substrate Lens Antenna (SLA). At sub-millimeter-wave frequencies, a SLA becomes unattractive because its diameter is typically larger than a free-space wavelength. Such lenses become heavy, bulky and expensive as the operating frequency is reduced. This thesis investigates electrically small, slot antenna fed, SLAs operating at 10 GHz in an attempt to facilitate the integration of these devices. (Abstract shortened by UMI.
Performance of a smart base station antenna in IS-136 cellular systems.
No full textComputer simulations have been used to study the effect of narrow switched-beam transmission and power control at the base station on the interference characteristics and traffic capacity of digital cellular (IS-136) systems. In simulations, four narrow beams in place of a sectored antenna pattern are used, and a power control mode with up to 30 watts maximum transmitted power is applied. Results indicate that with transmission on four narrow beams at the base station, the improvement in carrier to interference ratio (C/I) is more than 4 dB. Furthermore, with narrow beam transmission and the base station power control, the total improvement in C/I is 8 to 10 dB. If this C/I gain is utilized to maximize the amount of served traffic, the system capacity can be enhanced by more than 100%. Therefore, improvements in system performance with increased capacity and improved quality are expected by incorporating narrow beam transmission and base station power control
Investigation of HBT preamplification for high speed optical communication systems.
No full textA noise analysis for a Common-Collector-Cascode traveling wave HBT preamplifier is developed, resulting in an expression for the preamplifier's equivalent input noise current density. A photoreceiver, consisting of a P-I-N and GaAs HBT MMIC distributed amplifier, was implemented using Nortel's GaAs HBT (f T = 70GHz) process. The noise performance of the P-I-N preamplifier was predicted based on the noise analysis equations. The P-I-N preamplifier, having a measured bandwidth of 22GHz, displayed a measured average equivalent input noise current density of 24 pA/Hz . Good agreement was obtained between the predicted and measured noise performance. The analysis gives useful insight into the dominant noise contributions of the preamplifier. An 8-stage HBT distributed amplifier was successfully developed. By considering the various issues involved in its design, a design procedure for monolithic distributed amplifiers is presented. The implementation of the HBT preamplifier is described and its measured results are given. From the excellent agreement between the predicted and measured performance, the design method is considered validated. The successful operation of the distributed amplifier, which provides 15dB gain and 35GHz 3dB bandwidth, fulfills the objective of experimental verification. The implemented photoreceiver is the first to have a P-I-N mounted on the MMIC chip
Performance of a smart base station antenna in IS-136 cellular systems.
No full textComputer simulations have been used to study the effect of narrow switched-beam transmission and power control at the base station on the interference characteristics and traffic capacity of digital cellular (IS-136) systems. In simulations, four narrow beams in place of a sectored antenna pattern are used, and a power control mode with up to 30 watts maximum transmitted power is applied. Results indicate that with transmission on four narrow beams at the base station, the improvement in carrier to interference ratio (C/I) is more than 4 dB. Furthermore, with narrow beam transmission and the base station power control, the total improvement in C/I is 8 to 10 dB. If this C/I gain is utilized to maximize the amount of served traffic, the system capacity can be enhanced by more than 100%. Therefore, improvements in system performance with increased capacity and improved quality are expected by incorporating narrow beam transmission and base station power control
An automated matching network incorporating a six-port reflectometer
No full textIn this thesis an automated matching network is investigated as a means to reduce mismatch loss in circuits whose impedance characteristics vary during operation. The automated matching network incorporates a six-port network to measure impedance and a tunable circuit is implemented using varactor diodes to provide continuously variable impedances. A novel implementation for two-port measurements using a single reflectometer is presented.
The thesis concentrates on variable gain amplifier applications as these are common in wireless applications and matching is rarely maintained over the operating range of the device. A six-port reflectometer is implemented using off-the-shelf components. The tunable network is implemented using a miniature hybrid microwave integrated circuit (MHMIC) process with varactor diodes used as variable capacitances. Gain matching of a transistor amplifier is tested under various device biases.
The project establishes design guidelines for a tunable matching network using continuously variable impedances. The feasibility of the automated matching network concept is also proven. Based on the results, several proposals are made for future work using automated matching networks
Development of conformal reconfigurable metamaterial-based antennas
Full text linkAntennas are vital components of any wireless communication device. There has been a wide demand for novel flexible and reconfigurable wireless devices as a result of the rising user applications. This thesis presents the design of flexible low-cost antennas using metamaterial loadings with performance characteristics that can be reconfigured by employing microfluidics. In applications such as biomedicine, this work presents an inkjet-printed dipole antenna on flexible Kapton-foam substrate to be used on lossy host structures. The concept of Artificial Magnetic Conductor (AMC) unit cells is investigated for best impedance and gain performance. When integrated with a dipole radiator, the fabricated AMC-backed antenna maintains broadside radiation with gains of up to 4.8 dBi under planar and bending conditions, and on a lossy blood bag.
Antenna reconfiguration is then proposed by developing reconfigurable metasurface loadings implementing continuous-flow microfluidics and digital microfluidics. In the latter technique, a frequency reconfigurable AMC is designed using a pixelized approach with liquid metal interconnects. Simulations show that the pixelized design demonstrates switching by electric actuation between 2.45 GHz and 5 GHz depending on the state of the liquid metal interconnects. On the other hand, a multifunctional reconfigurable metasurface based on liquid metal injection (pressure) is presented. The reflective metasurface formed by two switchable microfluidic layers – top layer comprising an array of meandered half-rings and the lower layer, straight meander lines - can be reconfigured into four polarization states. The proposed metasurface becomes a reflector with emptied channels, whereas exhibits linear to cross polarization conversion (or linear to circular polarization conversion) properties when the top (or bottom) layer is filled with liquid metal alloy. The experimental results confirm the simulation results over the 8 GHz to 12 GHz test band.
The compactness, structural flexibility and multifunctionality of the proposed designs make them suitable candidates for modern integrated antenna array systems.University of Ontario Institute of Technolog
Physical optics analysis of electrically small slot-fed substrate lens antennas.
No full textWith the current explosion of microwave wireless communication systems comes the need to produce low cost miniaturized components. Integrated antennas, such as planar microstrip-fed patches and slots, are a promising means of combining the antenna function with the associated transceiver circuitry. However, these antennas suffer from a bi-directional radiation pattern, power loss via substrate modes, a broad radiation pattern, or a combination of the above. To correct these problems, a dielectric lens of hemispherical shape, or slight variation thereof, can be placed directly upon the planar antenna, forming what is called a Substrate Lens Antenna (SLA). At sub-millimeter-wave frequencies, a SLA becomes unattractive because its diameter is typically larger than a free-space wavelength. Such lenses become heavy, bulky and expensive as the operating frequency is reduced. This thesis investigates electrically small, slot antenna fed, SLAs operating at 10 GHz in an attempt to facilitate the integration of these devices. (Abstract shortened by UMI.
Compact integrated designs of microwave filters and antennas with dual-polarization
Full text linkMicrowave antenna and filter circuits are key components in all types of communication systems. In order to achieve high compactness and high performance for next generation wireless networks, this thesis investigates the use of a material with a high dielectric constant (approximately 20) and low loss for integrated design of microwave filters and antennas. Two different filtering antenna designs in the 3.5 – 3.7 GHz frequency range are presented. A dual-mode waveguide filter is used in both designs, while a microstrip antenna is used for one design and a dielectric resonator antenna (DRA) is used for the other. Microstrip antenna and DRA are used due to their low-profile, ease of fabrication and light weight. The integrated designs are validated using full wave electromagnetic (EM) simulations, showing comparable performances. Both designs are compact, low loss, and have dual-polarization with good isolation, making them ideal for 5G mobile communication applications.University of Ontario Institute of Technolog
Design of broad-band dual-polarized microstrip patch antennas with high port isolation for millimeter-wave 5G applications
Full text linkIn this thesis, multiple broadband dual linearly polarized antennas are designed covering the frequency band for the next generation of 5G communications around 28 GHz. Dual polarization antennas are employed to increase the capacity of the allocated spectrum through frequency reuse. Techniques for improving the impedance bandwidth is one of the most researched areas of microstrip antenna technology. New multi-layer dual linearly polarized design topologies are proposed in this thesis, based on substrate integrated waveguide (SIW) cavity-backed microstrip antennas. Different structures and materials, and antenna types are explored. Wide impedance bandwidths of around 34% to 47% are achieved. In addition to very wide impedance bandwidth, the designs have a profile that is nearly half that of similar antennas reported in the literature without degradation to the antenna front to back ratio or radiation performance. In addition, a technique to improve the port to port isolation of the antenna by more than 10 dB is proposed. All designs proposed here achieve isolation levels above 30 dB across the band of interest. Two antenna arrays, a four - and a sixteen-element are also designed based on the single element patch and fractal antennas. Their operational bandwidth is around 21% from 24 to 30 GHz, and sidelobe levels are better than 9 dB.
Simulation and optimization are carried out using full wave electromagnetic solver. A prototype of the final design was manufactured and tested. Results of all designs are compared and discussed for their bandwidth and the level of the port isolation in comparison to other millimeter wave dual linearly polarized antennas reported in the literature.University of Ontario Institute of Technolog
Design and measurement of antennas within lossy materials for IoT applications
Full text linkInternet of Things (IoT) technology for asset tracking in the transportation and logistics industry relies on wireless electronic communicating devices, often encapsulated with lossy filler materials which cause issues for the embedded antennas. This thesis studies methods of enhancing antenna radiation efficiency in such situations along with an improved, low-cost way of measuring radiation efficiency.
Multiple modified Wheeler caps are compared to a conventional design to obtain improved accuracy of the calculated radiation efficiency. The proposed adjustable-length Wheeler cap was verified in simulation and experimentally to significantly reduce the average error over a typical IoT antenna’s operating bandwidth. Furthermore, artificial magnetic conductors in conjunction with 1 cm3 air gaps are examined as methods of improving the radiation efficiency of both directional and omni-directional antennas placed near metal and encapsulated in resin, yielding up to 18% improvement in radiation efficiency
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