US 6,397,154 B1 · Correlation method for surveillance device detection

Abstract

A new correlation process and implementing apparatus for use in detecting the presence and location of a concealed eavesdropping device is disclosed in the present application. The process correlates a demodulated intercepted signal with a reference signal that corresponds to the sounds present in an environment of interest. A high correlation between the demodulated intercepted signal and the reference signal indicates that the demodulated intercepted signal corresponds to the audio in the environment of interest. An improved Correlation process is implemented using Fast Fourier Transforms to calculate a figure of merit based upon correlation data determined from sampled versions of the reference and intercept signals. The improved process and apparatus further provides a range to the detected surveillance device and multiple range measurements may be used to triangulate on the surveillance device to determine its precise location.

Claims35

Dependent claims

A method for detecting the presence of an electronic eavesdropping device that is transmitting a signal corresponding to ambient sounds in an environment, the method comprising:

generating a reference signal corresponding to the ambient sounds in the environment;
generating an intercept signal corresponding to demodulated audio from the transmitted signal of the electronic eavesdropping device present in the environment;
sampling the reference signal and the intercept signal to produce sampled reference signal data and sampled intercept signal data;
comparing said reference signal to said intercept signal to determine if an electronic eavesdropping device is present in said environment by performing a fast correlation process on the sampled data of intercept signal and reference signal to produce fast correlation data.

1 more element

An apparatus for detecting the presence of an eavesdropping device in an environment of interest, said apparatus comprising:

a transmitted signal receiver for intercepting transmitted signals in said environment of interest and producing an electronic intercept signal corresponding to said transmitted signals in said environment;
a reference signal generator for producing an electronic reference signal corresponding to said sound propagating through said environment;
a sampler for sampling said electronic intercept signal and said electronic reference signal during a sampling interval and producing digital intercept data and digital reference data;
and
a processor for comparing said reference signal to said intercept signal to determine if an electronic eavesdropping device is present in said environment by performing a fast correlation process on said digital reference data and said digital intercept data to produce fast correlation data.

2 more elements

Dependencies are inferred from the claim text.

Correlation method for surveillance device detection

Life of this patent

Correlation method for surveillance device detection

Life of this patent

Abstract

Claims35