Analysis of antenna structure with equal E- and H-plane patterns

An antenna structure consisting of an excited slot with two symmetrically disposed and parasitically excited monopoles is analyzed with the object of determining the optimum configuration such that equality is obtained between the E- and H-plane patterns. The analysis proceeds by treating the slot-monopole structure as a three-port network and taking into account coupling between different ports, so that the currents induced in the monopoles by the slot near field can be calculated. The far field is then obtained by superimposing the fields due to the monopoles and the slot. The height of the monopole and separation from the slot are then adjusted to give the desired equality between E- and H-plane patterns.