Grating Lobes Suppression of Patch Antenna Arrays Using Parasitic Monopoles

This work presents a technique to suppress the grating lobes of the antenna arrays that consists of large separated patch elements. The solution is based on modifying the patch radiation pattern using a parasitic monopole to suppress the grating lobes of the antenna array. The analysis of the combined structure is presented. The presence of the monopole modified the patch radiation pattern due to the coupling between them. This coupling as well as the induced current on the monopole are analytically calculated. The study provides the behaviour of the coupling for different separation distances and monopole dimensions. Then it is used to calculate the total radiation pattern of the single antenna element as well as the antenna array. Finally, the results are verified by the full-wave simulation.