Digital Mobile Passive Leak Detection for Broadband Communication System
First Claim
1. A detector for detecting a quadrature amplitude modulated (QAM) signal, said detector comprisinga mixer to mix a detected signal with an oscillator output wherein said oscillator is tuned to operate at a carrier frequency of a QAM band, to develop a quadrature baseband signal,a further mixer for mixing a signal corresponding to said quadrature baseband signal with an output of a further oscillator wherein said further oscillator is tuned to operate at a QAM symbol rate of said QAM band, anda processor to analyze a spectrum of an output of said further mixer to detect presence of a signal at a frequency corresponding to said QAM symbol rate.
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Abstract
Passive detection of a quadrature amplitude modulated (QAM) signal amid noise is achieved by detection of a spectral component of a detected signal that corresponds to a known QAM symbol rate in, for example, a QAM modulated broadband communication system (BCS). Improved authentication can be provided by simultaneously detecting symbol rate components in two or more QAM bands. No modification of a broadband communication system such as by including a marker signal is required and thus there is no requirement for dedication of a portion of the broadband communication system spectrum or problem of marker signal interference with BCS signals.
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Citations
20 Claims
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1. A detector for detecting a quadrature amplitude modulated (QAM) signal, said detector comprising
a mixer to mix a detected signal with an oscillator output wherein said oscillator is tuned to operate at a carrier frequency of a QAM band, to develop a quadrature baseband signal, a further mixer for mixing a signal corresponding to said quadrature baseband signal with an output of a further oscillator wherein said further oscillator is tuned to operate at a QAM symbol rate of said QAM band, and a processor to analyze a spectrum of an output of said further mixer to detect presence of a signal at a frequency corresponding to said QAM symbol rate.
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11. A method for detecting a quadrature amplitude modulated (QAM) signal, said method comprising steps of
mixing a detected signal with an oscillator output wherein said oscillator is tuned to operate at a carrier frequency of a QAM band, to develop a quadrature baseband signal, further mixing a signal corresponding to said quadrature baseband signal with an output of a further oscillator wherein said further oscillator is tuned to operate at a QAM symbol rate of said QAM band, and analyzing a spectrum of an output of said further mixer to detect presence of a signal at a frequency corresponding to said QAM symbol rate.
Specification