Chu-Limit-Guided Decomposition-Based Multiobjective Large-Scale Optimization for Generative Broadband Electrically Small Antenna Design

In traditional electrically small antennas (ESAs) design frameworks, overcoming the bandwidth limit derived from the Chu limit is considered unachievable. This paper proposes a three-dimensional (3-D) ESA configuration with high degrees of freedom (DoF), which is employed to significantly expand the design space for beyond-limit solutions. A revised multiobjective evolutionary algorithm based on decomposition (MOEA/D) is presented, which is guided by a Pareto front derived from the bandwidth limit to achieve rapid convergence. Prior knowledge, including structural priors, fabrication constraints, and physical interpretations of design parameters and objectives, is incorporated to efficiently generate effective solutions. The proposed method generates nine solutions, all of which exceed the bandwidth limits. A “radial-beamlet” antenna, fabricated using metal 3-D printing, achieves impedance bandwidth of 50.3% (2.05-3.43 GHz) and realized gain of 1.72-3.86 dBi. The bandwidth-efficiency product of the fabricated solution is 0.402, compared to the performance limit of 0.389. This approach pushes the boundaries of electrically small antennas and provides a new pathway for the advanced design of similar structures.