Digital mobile passive leak detection for broadband communication system
First Claim
1. A detector for determining presence or absence of a quadrature amplitude modulated (QAM) signal having a known symbol rate egressing from a broadband communication system (BCS), said detector comprisinga mixer to mix a signal received from an environment in a vicinity of said broadband communication system 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 determine said presence or absence of a signal at a frequency corresponding to said QAM symbol rate.
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Accused Products
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
22 Claims
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1. A detector for determining presence or absence of a quadrature amplitude modulated (QAM) signal having a known symbol rate egressing from a broadband communication system (BCS), said detector comprising
a mixer to mix a signal received from an environment in a vicinity of said broadband communication system 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 determine said presence or absence of a signal at a frequency corresponding to said QAM symbol rate.
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12. A method for determining presence or absence of a quadrature amplitude modulated (QAM) signal having a known symbol rate and egressing from a broadband communication system (BCS), said method comprising steps of
mixing a signal received by a receiver from an environment in a vicinity of said broadband communication system 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 determine presence or absence of a signal at a frequency corresponding to said QAM symbol rate.
Specification