US 2010/0246636 A1Published application

Detecting the Presence of Spread Spectrum Signals

AssigneeTelefonaktiebolaget L M Ericsson (publ)

InventorJacobus Haartsen

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Abstract

The presence of spread spectrum signals in a given frequency range is detected in a receiver by receiving a signal; determining for a measurement frequency an indication signal; and using it as an indication of the presence of spread spectrum signals having a carrier frequency equal to said measurement frequency. An in-phase signal and a quadrature signal are provided by mixing the received signal with an oscillator signal having said measurement frequency; at least one of these signals is phase shifted; a sum signal and a difference signal 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.

Claims14

Dependent claims

A method of detecting, in a receiver for radio frequency signals, the presence of spread spectrum signals in a given frequency range, the method comprising the steps of:

receiving a signal in said frequency range;
determining for a measurement frequency in said frequency range an indication signal from the received signal;
and
using the determined indication signal as an indication of the presence of spread spectrum signals having a carrier frequency equal to said measurement frequency,
wherein the step of determining the indication signal further comprises the steps of:
providing an in-phase signal and a quadrature signal by mixing the received signal with a locally generated oscillator signal having said measurement frequency;
phase shifting at least one of said in-phase signal and said quadrature signal to provide two phase aligned signals;
generating a sum signal of said phase aligned signals and a difference signal between said phase aligned signals;
multiplying said sum signal by said difference signal to provide a multiplied signal;
and
low pass filtering said multiplied signal to provide said indication signal.

8 more elements

A receiver for radio frequency signals, arranged to detect the presence of spread spectrum signals in a given frequency range, the receiver comprising:

means for receiving a signal in said frequency range;
circuitry for determining for a measurement frequency in said frequency range an indication signal from the received signal;
and
control circuitry arranged to use the determined indication signal as an indication of the presence of spread spectrum signals having a carrier frequency equal to said measurement frequency,
wherein the determining circuitry comprises:
mixers arranged to provide an in-phase signal and a quadrature signal by mixing the received signal with a locally generated oscillator signal having said measurement frequency;
phase shifting means arranged to phase shift at least one of said in-phase signal and said quadrature signal to provide two phase aligned signals;
adders arranged to generate a sum signal of said phase aligned signals and a difference signal between said phase aligned signals;
a multiplying circuit arranged to multiply said sum signal by said difference signal to provide a multiplied signal;
and
a low pass filter arranged to filter said multiplied signal to provide said indication signal.

8 more elements

Dependencies are inferred from the claim text.