Matching of microstrip patch array antennas with reflectors

This paper presents an impedance matching technique for microstrip patch array antennas based on reflectors. It is necessary to adjust the size of these parasitic patches and also the distance between them and the square patches of the antenna in order to obtain a proper impedance matching as well as a correct balance between front-to-back ratio, antenna directivity and bandwidth. The proposed structure consists of microstrip reflectors and square patches inset fed by a corporate-feed network that goes through the reflectors to connect the square patches. In this new design, the parasitic patches are joined lengthwise in order to create a single reflector for the whole antenna that enhances significantly the bandwidth and improves return loss at working frequency. The feed network is designed with quarter wavelength impedance transformers in order to match 100Ω patch elements to a 50Ω input, due to reduce losses caused by mismatch at the interface between the feed network and the antenna. Simulation results are presented in this paper to demonstrate the benefits of the microstrip reflectors joined together with the appropriate feed network.