A cellular antenna having an array of radiating elements and a flat sheet of dielectric material in front of the antenna radiating elements and spaced about a half wavelength from the antenna phase center to provide an azimuth beam width that is narrower than without the dielectric sheet. The sheet of dielectric material may be continuous or segmented and a single layer or multi-layer. The amount of narrowing may be controlled by changing the thickness and dielectric constant of the dielectric sheet.