A DEVICE FOR RECEIVING A RADIO FREQUENCY SIGNAL IN A FREQUENCY BAND

摘要

Devices (10) comprising antennas (1) for receiving radio frequency signals in frequency bands are provided with circuits (2) for tuning the antennas (1) to the frequency band as well as for, in response to feedback signals, increasing efficiencies of combinations of the tuned antennas (1) and the circuits (2). Such devices (10) are simple and low cost. The antennas (1) are electrical antennas having an electrical length of at most 20% of a wavelength of the frequency band and having an omni directional radiation pattern. Amplifiers (3) amplify antenna signals originating from the antennas (1) via the circuits (2) and supply the feedback signals to the circuits (2). A feedback between the amplifiers (3) and the circuits (2) is a positive feedback and is such that the amplifiers (3) are stable. The circuits (2) comprise coils (21) for tuning the antennas (1) and further coils (22) or capacitors (23,24) for receiving the feedback signals from the amplifiers (3).