An antenna (80,90) has a one dimensional or multidimensional array of elements (20,40), wherein spacings between successive elements of at least part of the array are non periodic and correspond to a series of multiples of a unit spacing, the multiples following a Fibonacci sequence. Two dimensional arrays can be arranged as a Fibonacci grid or as a Fibonacci square tiling. The number of elements can be reduced for a given measure of resolution, while still enabling the signal being transmitted or received to have a peak in a single unique direction and thus form a beam. Furthermore, since there will be some elements clustered close together and a few which are well spaced, it can be more suitable for vehicles (30) than a regularly spaced array. It can be used as a transmit antenna or as a receive antenna for a submillimeter radar system.