DETECTION OF MICROPHONE WITH RADIO TRANSMITTER AND DEVICE FOR ITS IMPLEMENTATION Russian patent published in 1997 - IPC

FIELD: radio engineering, detection of microphone with transmitter installed without authorization in limited space. SUBSTANCE: proposed process includes radiation of acoustic signal, reception of radio frequency signals, demodulation and filtration of signals. Radio frequency signals are received beyond limits of limited space in two points of limited space as minimum and are processed by Fourier transform comparing intensities of spectral components for each radio frequency. Those signals which have bigger or equal intensities in two points of limited space in comparison with intensities of spectral components of radio signal beyond limits of limited space are extracted. Then radio signals with specified spectral components are received, acoustic signal has duration ΔT, demodulated signals within interval ΔT are processed by Fourier transform at least twice. Device for implementation of detection has former of acoustic signal and radio receiver composed of mixer, discriminator, indicator connected with outputs to inputs in series and local oscillator. Device is supplemented with two antennas, antenna commutator, analog-to-digital converter, unit of on-line storages, Fourier transform unit, threshold unit, unit of comparators, on-line storage, code converter, electronic controlled switch, control unit. Local oscillator is manufactured in the form of digital synthesizer and indicator displays spectral components. EFFECT: enhanced reliability of detection. 8 cl, 14 dwg