A frequency offset booster with an oscillation prevention function for land mobile communication

The apparatus and experimental results of the FOB are described in this paper. The frequency offset booster (FOB) is a new reradiation system for mobile communications. Reradiation systems boost radio signals both from a cell sites and mobile stations in poor signal reception areas, using the same transmit frequency as the receive frequency. Because there is the danger of oscillation with re-radiation systems used in the open-air caused by spillover signals from the transmit antenna to receive antenna, their use in open-air areas is strongly restricted. The FOB can measure the amount of spillover signal, and maximizes the re-radiation gain with preventing oscillation. The FOB consists of a frequency converter, a spillover signal detector and a gain controller in addition to the fundamental components of a re-radiation system. It slightly offsets the transmission frequency from reception frequency. The spillover signal detector measures the offset frequency component in the received signal.