Abstract:
A disturbance, such as vibration from human activity, is located along a fiberoptic waveguide configuration (301-304) with two interferometers (801, 802) of the same or different types, such as Mach-Zehnder, Sagnac, and Michelson interferometers. Carrier signals from a source (101) are split at the interferometer inputs (201, 202) and re- combined at the outputs (701, 702) after propagating through the detection zone (401), where phase variations are induced by the disturbance (501). Phase responsive receivers (901, 902) detect phase relationships (1001, 1002) between the carrier signals over time. A processor (1101) combines the phase relationships into composite signals according to equations that differ for different interferometer configurations, with a time lag between or a ratio of the composite signals representing the location of the disturbance. The detected and composite values are unbounded, permitting phase displacement to exceed the carrier period and allowing disturbances of variable magnitudes to be located.
Abstract:
An intrusion detection system and method utilizing a power transmission cable (280) connected to a source of radio frequency signal (282). A data transmission cable (270) is associated with the power transmission cable (280) and is provided with a plurality of radio frequency identification chips (272, 274, and 276). The power transmission cable (280) would induce an electromagnetic field within the data transmission cable (270) allowing each of the RFID chips to transmit a signal during normal operation. However, if an intrusion occurs or the power transmission cable (280) or data transmission cable (270) is severed, the system according to the present invention, would be able to determine the exact point of intrusion based upon the signals received or not received from the RFID chips.
Abstract:
A system, device, and method for monitoring an uncontrolled area around a mobile object uses a distributed antenna, which can be a leaky coaxial cable, enclosing its perimeter. A field disturbance sensor, such as a microwave sensor, detects an intruder entering a protected area defined by field of the antenna. An alarm signal is sent to a wireless transceiver for transmission of an alarm event to a remote station. A biometric sensor, such as a passive infrared heat detector, can be used in conjunction with the field disturbance sensor to reduce possible false alarms. Identification of a legitimate alarm may alternatively be verified with video images obtained near an area of interest in proximity to the mobile object, which may be forwarded by the wireless transceiver to a remote station for analysis.
Abstract:
The present invention relates to a monitoring device (1) with a transmitter unit (2) and a receiver unit (3) for monitoring an area. Slotted cables serve as antennas. According to the invention, a first slotted cable is arranged as a transmitting a antenna (4) for transmitting a pulsed high-frequency signal and a second slotted cable is arranged as a receiving antenna (9) for receiving the reflected signal. The slotted cables are arranged in association with each other and essentially parallel to each other, and the transmitter unit (2) is connected to the first slotted cable at one end of the antenna arrangement and the receiver unit (3) is connected to the second slotted cable at the other end of the antenna arrangement.
Abstract:
In an intrusion detection system of the kind which comprises a "leaky cable" or open transmission line and is used to determine the presence of objects, things or people moving in the vicinity of the leaky cable, a transmitting antenna (10) and a receiving antenna (18), one of which is an open transmission line/leaky cable, are connected to a transmitter unit (14) and a receiver unit (18), respectively. A control unit (26) controls both the transmitter unit (14) and the receiver unit (18), and causes the receiver unit (18) to scan a preselected radio band, with the transmitter unit (14) not transmitting, to detect one or more relatively quiet portions of the band in which instant received signal levels are lower than a predetermined threshold. The control unit (26) selects a plurality of disparate frequencies in such one or more relatively quiet portions and subsequently causes the transmitter unit (14) to transmit signals by way of the transmitting antenna (10) at the disparate frequencies. The receiver unit (18) receives signals corresponding to the transmitted signals and the control unit (26) detects perturbations in the received signals caused by an intruder in the vicinity of the leaky cable to determine the presence of the intruder. The disparate frequencies may have a bandwidth equal to at least 5 per cent and preferably about 10 per cent of their mean frequency. Operation in the quiet bands allows frequency diversity to be employed, reducing the effects of standing waves and allowing the leaky cable to be deployed without a surrounding electrically-lossy medium, for example above ground, while providing uniform detection sensitivity.
Abstract:
An intrusion detection system comprises a plurality of sensors (2A...2X) and a corresponding plurality of receivers (3A...3X). Each receiver receives, via the associated sensor, radio frequency signals comprising a multiplicity of transmissions at different frequencies within a predetermined frequency spectrum. The receiver detects the radio frequency signals and computes, for each of a plurality of successive time intervals and for each of the transmission frequencies, a measurement of signal amplitude over the time interval; compares such signal amplitude measurement with at least one threshold and, if the amplitude exceeds the threshold for a predetermined time period, generates a potential alarm signal. A processor (4) compares potential alarm signals from a plurality of sensors and determines that an intrusion has occurred if the potential alarm signal for a particular station does not coincide with a potential alarm signal for a neighbouring sensor. Each receiver may output an intruder alarm signal when potential alarm signals occur simultaneously for more than a preset number of a multiplicity of the transmission frequencies.
Abstract:
An open transmission line system for locating an entity (110) moving along a defined pathway uses transmissions from a remote, independent transmitter (106), conveniently a commercial radio or television station. The system comprises two receivers, both tuned to the frequency of the transmission. One receiver (101) receives signals directly from the transmitter (106) by means of an antenna (104). The other receiver (102) receives the signal from the transmitter (106) by way of an open transmission line (107). A processor (103) processes the signals from the two receivers to detect the entity. The system may use transmissions at different frequencies from plural mutually-spaced transmitters (402; 403; 404) in order to provide reliability and to minimize the effects of multipath signals. The system may employ a variable velocity open transmission line (507), comprising a central conductor means (1100) having a permeable central element (1202) carrying a helically wound conductor (1201). The inductance of the cental conductor, and hence the propagation rate of the line is varied by means of a periodically varying signal (Vm) applied to the conductor. The entity causes different phase variations at the different propagation rates. The processor (103) compares these phase variations to locate the entity.
Abstract:
Systems, apparatus and methods are provided for measuring moving vehicle information. Moving vehicle information may be measured by a sensor configured to respond to one or more wheels of the moving vehicle, where one or more of the wheels change the characteristic impedance of the sensor at the wheel's contact location. An electrical time domain reflectometry signal processing system which is capable of measuring the change in the impedance of the sensor and converting the impedance change to a signal may be connected operatively to the sensor. A data-processing system receives the signal and extracts the moving vehicle information therefrom.
Abstract:
A system (10) for protecting a border (B) comprises a fiber-optic cable (12) extending from one end of a border to the other end thereof. The cable includes a bundle of optical fibers which connect to sensors placed at intervals long the border. Included within the fiber-optic cable is a high voltage conductor by which high voltage AC is introduced into, and passes through, the cable for powering the sensors. The high voltage is stepped down and rectified from AC to DC for this purpose. Various types of sensors (100-700) are arranged in pods (14) located at intervals along the length of the border. A method of border protection is also disclosed.