Evolutionary Algorithms Applied to Cross Aperture Coupled Circularly Polarized Microstrip Antenna

Utilizing evolutionary algorithms to achieve a low axial ratio of a circularly polarized microstrip antenna over a wide bandwidth and optimal impedance matching is the main aim of this study. A circularly polarized cross aperture coupled microstrip antenna using a 50Ω microstrip feed line is designed. A software simulation program (CST microwave studio) is used to design and compare the performance of the antenna in terms of return loss and axial ratio. Two distinct evolutionary algorithms; Particle Swarm Optimization (PSO) and Genetic Algorithm (GA) have been applied to optimize the fitness function to ensure optimal axial ratio and impedance matching. The optimal patch dimensions, the aperture length, and the microstrip feed line length are obtained from both methods and their performances are compared. Moreover, the antenna is fabricated and the return loss is measured using a network analyzer. A comparative analysis is carried out demonstrating a high agreement between measured and simulated return loss.