Circuit-Theoretic Physics-Based Antenna Synthesis and Design Techniques for Next-Generation Wireless Devices

摘要

Performance levels expected from future-generation wireless networks and sensor systems are beyond the capabilities of current radio technologies. To realize information capacities much higher than those achievable through existing time and/or frequency coding techniques, an 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. The antenna configuration should also be highly miniaturized and integrated with circuits around it in order to meet the rigorous requirements of size, weight, and cost. A solid understanding of the underlying physics of the antenna function is, and has always been, the key to a successful design. In a typical antenna design process, the designer starts with a simple conceptual model, based on a given volume/space to be occupied by the antenna. The design cycle is 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, a large variety of design approaches and steps exist. These 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 due to the many uncertainties and ‘unknowns’ in the antenna problem, a final working design is usually an evolved version of an initial implementation that comes to fruition only after a considerable amount of effort and time spent on “unsuccessful” prototypes. In general, 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 a fairly well-defined procedure, from the conceptual stages to the actual realization. In view of the aforementioned, this work 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 wideband antennas, and an Eigen-based technique to realize multi-band/multi-feed antennas, tunable antennas, and high sensitivity sensor antennas. By utilizing the proposed approaches in the context of this research, the design cycle for practical antennas should be significantly simplified along with various physical limitations clarified, all of which translates to reduced time, effort, and cost in product development.