There is disclosed a directional multi-band antenna comprising: a primary reflector, at least one secondary reflector, a multi-layer dielectric layer selectively reflective or transmissive of incident radiation according to wavelength, the layer being provided at the surface of either the primary or the secondary reflector, an RF unit comprising a collocated sensor and transmitter, an Optical unit comprising a collocated sensor and transmitter, arranged such that the primary reflector is for passing signals between the secondary reflector and the environment, the secondary reflector is firstly for passing signals between the primary reflector and the RF unit, and secondly for passing signals between the primary reflector and the Optical unit and arranged such that the antenna is operable to transmit or receive, RF or Optical signals, along a common beam axis.