A transmitter or a method for transmitting data from a first antenna imposes a low level phase modulation, for example of less than 90, on a carrier signal in accordance with a data signal to create a modulated signal, preferably having a carrier frequency and sidebands, and the sidebands may be substantially lower in amplitude than the carrier frequency. The method may be used in an identification system, for example for identifying luggage or other items. In another aspect of an apparatus or method for transmitting data, a phase modulation may be imposed on a carrier signal in accordance with a data signal to create a modulated signal having a carrier and sidebands, where the amount of phase modulation being selected is such that the amplitude of the sidebands is substantially lower than that of the carrier. Phase modulation may be imposed by a mixer.