Pixel Antenna Optimization Using $N$ -Port Characteristic Mode Analysis

A method for using N-port characteristic mode analysis (N-port CMA) for the design and optimization of pixel antennas is described. The motivation for using N-port CMA is to determine the fundamental resonance characteristics of the pixel antenna geometry and optimize them directly. An advantage of this approach is that it separates the process of antenna resonance optimization from impedance matching. It contrasts directly with conventional optimization approaches based on return loss which implicitly perform impedance matching together with antenna resonance optimization. In our work, an objective function based on modal significance is utilized and genetic optimization is used to optimize the desired characteristics. An efficient method for the implementation of N-port CMA is described which requires only one full-wave simulation of the pixel geometry in the optimization process. Impedance matching is performed as a final step in the design process after optimization of the antenna resonance is completed. Simulation and experimental results are provided to demonstrate the utility of the approach. Examples include a triband antenna design for GSM900 (880-960 MHz), DCS1800 (1710-1900 MHz), and IMT-E2600 (2500-2690 MHz), and a dual-band antenna design for GSM900 (890-960 MHz) and DCS + PCS + UMTS bands (1710-2170 MHz).