Evolutionary optimization of asymmetrical pixelated antennas employing shifted cross shaped elements for UHF RFID

Abstract

The design and optimization of antennas for specific boundary conditions and parameters, such as size and frequency, for a given application, is a highly complex and time consuming process, which usually involves elaborate computer-aided software packages and/or methods. Additionally, trade-offs and co-dependencies have to be considered, when optimizing for a specific parameter, i.e., a high antenna gain goes usually hand-in-hand with a large antenna. Therefore, we implemented a method that involves the automated design and optimization of asymmetrical pixelated antennas using evolutionary algorithms, where arbitrary parameters can be optimized for chosen boundary conditions. In contrast to other approaches, shifted cross elements were employed as pixels to avoid point contact defects. We present results for antennas with an exemplary resonant frequency of 868 MHz and sizes of 3 × 3, 4 × 4 and 6 × 6 cm. The agreement between measurements and simulations for the antenna gain and reflection coefficient is excellent, with a maximum error of 1.15% for the single resonant frequency (relative error) and 1.35 dB for the antenna gain (mean absolute error).