NCJ Number
57863
Date Published
1978
Length
40 pages
Annotation
A MOBILE INTRUDER DETECTION SYSTEM, OPERATING IN THE VERY HIGH FREQUENCY (VHF) RANGE, HAS BEEN SUCCESSFULLY TESTED FOR ISOLATED OR CLUSTERED HIGH-VALUE RESOURCES TO REDUCE FALSE ALARM RATES.
Abstract
THE SYSTEM CAN BE USED TO PROTECT INDIVIDUAL OR CLUSTERED VEHICLES, STORAGE AREAS, FIELD SITES, AND PARKED AIRCRAFT IN THE MILITARY SERVICES AND CIVILIAN GOVERNMENT AGENCIES. IT CAN BE EMPLOYED AS A QUICK-REACTION PORTABLE SYSTEM OR AS A PERMANENTLY-INSTALLED SYSTEM. ELEMENTS OF THE SYSTEM INCLUDE A DISTRIBUTED TRANSMITTING NETWORK, A RECEIVING COMPONENT, AND ASSOCIATED SIGNAL PROCESSING CIRCUITRY. THE TRANSMITTING COMPONENT IS A LENGTH OF LEAKY (PORTED) COAXIAL CABLE ON THE GROUND, LOOPED AROUND THE RESOURCE TO BE PROTECTED. A CENTRALLY LOCATED ANTENNA RECEIVES THE RADIATED SIGNAL. WHEN AN INTRUDER CROSSES THE CABLE, THE RECEIVED SIGNAL CHANGES FROM ITS QUIESCENT LEVEL. THIS CHANGE IS THEN DETECTED AND PROCESSED, SETTING OFF AN ALARM. AN EXPERIMENTAL PROGRAM WAS INITIATED TO EVALUATE THE OPERATION OF THE SYSTEM. TESTS WERE DESIGNED TO ESTABLISH THE VALIDITY OF ELECTROMAGNETIC PRINCIPLES, TO OBSERVE SYSTEM PERFORMANCE IN A REALISTIC ENVIRONMENT, AND TO IDENTIFY ANY WEAKNESSES WHERE FURTHER REFINEMENT OF THE SYSTEM WOULD BE NECESSARY. TEST RESULTS SHOWED THAT THE SYSTEM PROVIDES FULL AZIMUTHAL COVERAGE WITH VHF OPERATION AND IS RESISTANT TO SIGNAL MASKING CAUSED BY ISOLATED OR CLUSTERED RESOURCES WITHIN PROTECTIVE BOUNDARIES. THE SIZE OF VHF WAVELENGTHS HELPS TO DISCRIMINATE BETWEEN REAL INTRUSIONS AND FALSE OR NUISANCE ALARMS. POWER REQUIREMENTS OF THE SYSTEM ARE MINIMAL. THE SYSTEM IS VERSATILE AND HAS POTENTIAL FOR USE IN QUICK-REACTION MOBILE CONFIGURATIONS. ILLUSTRATIONS, PHOTOGRAPHS, AND REFERENCES ARE INCLUDED. (DEP)