Effect of a Central Antenna Element on the Directivity, Half-Power Beamwidth and Side-Lobe Level of Circular Antenna Arrays

This paper analyses the effect of a central antenna element on the radiation pattern in a uniform circular antenna array. A modification of the array geometry is considered in which one of the antenna elements is placed in the center of the array. The corresponding array factor is adjusted to describe the geometric configuration that includes the central antenna element. This distribution alters the radiation pattern in such a way that the array directivity and half-power beamwidth are affected. An increase on the directivity and a decrease of the half-power beamwidth are obtained by adjusting the phase of the central element. A reduction of the side-lobe levels is also achieved. Array configurations with different number of antenna elements were tested as well, and the results on directivity and half-power beamwidth are presented. Using Microstripes, a software tool that enables the simulation of antennas, a 6-element circular antenna array was designed and the directivity for a range of frequencies was obtained.