Genetic Algorithm-based Design Optimisation of Aperture-coupled Rectangular Microstrip Antenna

The technique of feeding a microstrip antenna with a microstrip line through an aperture is gathering a lot of interest in communication and radar systems used for defence applications. This is due to the fact that this feeding technique has many adjustable parameters in the form of aperture length, width, and stub parameters. This paper presents a study on the effect of aperture dimensions and stub length on the voltage-standing wave ratio bandwidth of an aperturecoupled microstrip antenna. Without any additional matching network, optimal impedance matching of the antenna has been achieved using genetic algorithm. In the algorithm, each chromosome consists of three binary encoded genes, one for aperture length, second one for aperture width and the last one for stub length. Finally, the algorithm determines the parameters of the antenna that provides the minimum value of the average reflection coefficient. The investigation is made at different microwave frequency ranges and it extends up to Ku band. The results show that the percentage of fractional bandwidth improves for higher design frequencies and has a maximum of 13.2 per cent for centre frequency of 17.5 GHz. Experimental results are presented for a particular range of frequency and the accuracy of the analysis is briefly discussed.