DETECTING THE PRESENCE OF SPREAD SPECTRUM SIGNALS

摘要

The presence of spread spectrum signals in a given frequency range is detected in a receiver (10) by receiving a signal; determining for a measurement frequency (?o) an indication signal; and using it as an indication of the presence of spread spectrum signals having a carrier frequency (?c) equal to said measurement frequency (?o). An in-phase signal (B) and a quadrature signal (C) are provided by mixing the received signal with an oscillator signal having said measurement frequency (?o); at least one of these signals is phase shifted; a sum signal (E) and a difference signal (F) are generated; and the sum signal is multiplied by the difference signal and low pass filtered. In this way a method and a circuit of detecting the presence of spread spectrum signals in a given frequency range are provided, which are simple and fast enough to be used in low-cost cognitive radios.