George S.A. Shaker
Circuit-Theoretic Physics-Based Antenna Synthesis and Design Techniques for Next-Generation Wireless Devices
Safavi-Naeini, Safieddin and Sangary, Nagula (Adjunct)
Performance levels expected from future generation wireless networks and sensor systems are clearly beyond the capabilities of current radio technologies. To realize information capacities much higher than what are achievable through existing time and/or frequency coding techniques, the antenna system must exploit the spatial characteristics of the medium in an intelligent and adaptive manner. This means that such system needs to incorporate integrated multi-element antennas with controlled and adjustable performances. Furthermore, the antenna configuration should be highly miniaturized and integrated with circuits around it in order to meet the very demanding, size, weight, and cost requirements.
A solid understanding of the underlying physics of the antenna function is, and has always been, the key for a successful design. In a typical antenna design process, the designer starts with a simple conceptual model, based on a given constrained volume/space to be occupied by the antenna. The design cycle is marked completed by the antenna performing its function over a range of frequencies in some complex scenarios, i.e. packaged into a compact device, handled in different operational environments, and possibly implanted inside a human/animal body. From the conceptual model, to the actual working device, there exists a large variety of design approaches and steps. Such approaches may be viewed as simulation-driven steps, experimental based ones, or a hybrid of both. In any of these approaches, a typical design involves a large amount of parametric/optimization steps. It is no wonder then that there are lots of uncertainties and unknowns in the antenna problem that a final working design is typically an evolved version of an initial implementation after a considerable amount of effort and time spent on sets of "unsuccessful" prototypes. On the other hand, the circuit/filter community has enjoyed a "better" design experience than that of the antenna community. Designing a filter network to meet specific bandwidth and insertion loss is fairly a well-defined procedure from the conceptual stages to the actual realization.
In view of the aforementioned facts, this work primarily focuses on attempting to unveil some of the uncertainties associated with the general antenna design problem through adapting key features from the circuit/filter theory. Some of the adapted features include a group delay method for the design of antennas with a pre-defined impedance bandwidth, inverter-based modeling for the synthesis of small-sized yet wideband antennas, and an Eigen-based technique to realize multi-band/multi-feed antennas, tunable antennas, and high sensitivity sensor antennas. Utilizing the proposed approaches in the context of this research, it is believed that the design cycle for practical antennas should be significantly simplified, with several physical limitations clarified, reflecting on the effort, time and cost spent on product development.