Electronic surveillance device detector and method using phase a

Details Electronic surveillance device detector and method using phase a Electronic surveillance device detector and method using phase a

1990-09-10

1993-08-31

Eisenzopf, Reinhard J.

Telecommunications

Receiver or analog modulated signal frequency converter

Responsive to an input signal of particular predetermined...

455 672, 4552264, 379 7, H04B 116

Patent

active

052416992

ABSTRACT:
The disclosed invention detects electronic surveillance devices. Should an electronic surveillance device (a bug) be present in a room, the bug will be detecting sounds with a microphone and transmitting on some electromagnetic frequency. In the present invention, these signals are received by a receiver which produces a receiver signal, and a microphone converts the sound present in the room into an electronic reference signal. As may be noted both the received signal from the electronic surveillance device and the reference signal from the reference microphone will have as their source the sounds that are within the room. It is this common sound source of both signals that allows the presence of an electronic surveillance device to be detected. According to the present invention, the phase angle difference between the receiver signal and the reference signal is examined in order to decide if there is any phase correlation. Should the received signal and the reference signal be either in phase, or have relatively constant phase angle differences, then an electronic surveillance device is present in the room. In addition to detection, the present device may be used to locate the electronic surveillance device by movement of the reference microphone. By moving the reference microphone and noting the variation in the phase angle and signal correlation level, an operator may move the reference microphone until the phase angle difference is minimized. At this point, the reference microphone may be in close proximity to the electronic surveillance device and a non-electronic search for the device may be instituted.

REFERENCES:
patent: 4218592 (1980-08-01), Steinbergs et al.
patent: 4658099 (1987-04-01), Frazer
patent: 4797635 (1989-01-01), Hatcher
patent: 5034963 (1991-07-01), Singer

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