Size reduction of ultra-wideband antennas with efficiency and matching constraints

Antenna design is a multifaceted task that involves handling of various performance figures concerning both electrical performance of the structure as well as its geometry. Simultaneous control of several objectives through rigorous optimization is very challenging and virtually impossible through conventional approaches such as parameter sweeping. In this work, we investigate size reduction of ultra-wideband antenna structures while taking into account the reflection response and total efficiency. Available design trade-offs concerning the antenna footprint, its wideband matching, and efficiency are identified through numerical optimization. More specifically, the goal is to identify designs that exhibit the minimum possible footprint while maintaining the maximum in-band reflection and average efficiency within the prescribed thresholds. This is realized by appropriate formulation of the objective function exploiting a penalty function approach. Our methodology is demonstrated using an ultra-wideband monopole antenna example. As an extension, a 3-objective Pareto set is further generated using surrogate modeling and multi-objective evolutionary algorithm. A set of designs generated this way provides a designer with a comprehensive knowledge about the capabilities of a given antenna structure and facilitates a decision-making process driven by a particular application and performance requirements.