Abstract: An antenna for transmitting or receiving electromagnetic radiation along an axis comprises at least three layers 20a, 20b, 20c, 20d and 20e of dielectric material spaced from one another in a direction perpendicular to the axis. The outermost layers 20a and 20e are spaced from one another by at least half the wavelength of the electromagnetic radiation. The layers extend generally in the direction of the axis from a rear end to a front end of the layers. A transition portion 22 electromagnetically couples the layers 20a, 20b, 20c, 20d and 20e directly to a waveguide 21. A front end of the transition portion 22 is connected to the rear end of the layers 20a, 20b, 20c, 20d and 20e and has a dimension in the direction perpendicular to the axis substantially equal to the spacing between the outermost layers 20a, 20e at the rear end of the layers.