WO2006091192A2

WO2006091192A2 - Communications-based apparatus and method for detecting a breach in the integrity of a container

Info

Publication number: WO2006091192A2
Application number: PCT/US2005/005474
Authority: WO
Inventors: Julio I. Concha; Jae-Hyuk Oh; Adrian M. Thompson; Ketki P. Vahalia; Joseph Zacchio
Original assignee: Chubb International Holdings Ltd
Current assignee: Chubb International Holdings Ltd
Priority date: 2005-02-22
Filing date: 2005-02-22
Publication date: 2006-08-31
Anticipated expiration: 2007-08-22
Also published as: WO2006091192A3

Abstract

A breach (14) in the integrity of a container (10), such as a cargo container or a security vault, is detected using a system (12) formed of at least one transmitter (18) and at least one receiver (20) oppositely positioned either inside or outside of the container (10). Each transmitter (18) transmits a signal, while each receiver (20) attempts to detect the signal. The receiver (20) evaluates a power of the signal to determine whether a breach (14) in the integrity of the container (10) has occurred.

Description

COMMUNICATIONS-BASED APPARATUS AND METHOD FOR DETECTING A BREACH IN THE INTEGRITY OF A CONTAINER

BACKGROUND OF THE INVENTION The present invention relates generally to the field of security, and more particularly, to an apparatus and a method for detecting a breach in the integrity of a cargo container.

Due to increased criminal activities, such as people trafficking and the threat of container-borne terrorist attacks, the security of cargo containers has received increased attention. Until recently, security procedures for cargo containers have relied upon visual inspections and some limited automation, notably, electronic door locks and seals. Such security measures, however, are lacking. While electronic door locks and seals can raise an alarm if the seal is broken or if the door is opened or removed, they cannot monitor the integrity of the container structure itself.

Very few commercially available products exist to detect breaches in the integrity of the container structure itself. One such system relies upon light sensors that respond to externa! light that may become visible when a hole is cut through a wall of the container or the container door is opened. However, these systems do not work if there is no external light, such as occurs at night or inside a dark warehouse or ship. Moreover, the contents of the cargo container themselves may block any light from reaching the sensor.

Accordingly, there remains a need for new automated systems for monitoring the integrity of cargo containers.

BRIEF SUMMARY OF THE INVENTION

The present invention is premised upon the fact that a typical cargo container is essentially an imperfect Faraday cage, in that, when sealed (i.e., when the doors are closed), the passage of electromagnetic waves through the walls of the container is substantially blocked. A security system in accord with the present invention includes at least one transmitter and at least one receiver oppositely positioned either inside or outside of the container. Each transmitter transmits a signal, while each receiver attempts to detect the signal. The receiver evaluates the signal power to determine whether a breach in the integrity of the container has occurred.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic drawing of a first embodiment of a security system for use in detecting a security breach in the integrity of a container having characteristics of a Faraday cage.

FIG.2 is a schematic drawing of a second embodiment of a security system for use in detecting a breach in the integrity of a container having characteristics of a Faraday cage. FIG. 3 is a block diagram of one of a plurality of security devices of the security system of FIG. 2.

FIG. 4 is a plot of the power of a signal received by a receiver positioned inside a container having characteristics of a Faraday cage from a transmitter positioned outside of the container with respect to time. DETAILED DESCRIPTION

FIG. 1 is a schematic drawing of container 10 along with security system 12 for use in detecting security breach 14 in the integrity of container

10. As shown in FtG. 1 , security breach 14 is a hole in wall 16 of container

10. However, security breach 14 may also be the opening of door 17 of container 10, which is basically nothing more than a large hole in wall 16.

Container 10 is essentially a Faraday cage through which minimal or no electromagnetic radiation is allowed to transfer. As such, container 10 may be a cargo container, a bank vault, a motor vehicle, or another structure substantially immune to the passage of electromagnetic radiation. For instance, container 10 may also be a nonmetallic container coated with a metallic paint or a building formed of either plaster with metal mesh or rebar concrete.

Security system 12 includes external transmitters 18a, 18b, and 18c

(collectively transmitters 18) and internal receiver 20. Each transmitter 18 includes at least one antenna positioned outside container 10 and circuitry both for generating a signal having a frequency f₀ and for transmitting that signal to the antenna for radiation as electromagnetic waves. In one embodiment, the transmitted signal is a radio or microwave frequency signal. Transmitters 18 may be line- and/or battery-powered devices. For instance, where container 10 is a cargo container located in a shipping yard, it may be preferred to have transmitters 18 connected to line power. But, where container 10 is a cargo container located on an ocean-going freight ship, it may be preferred to have transmitters 18 be self-sufficient and battery- powered.

Receiver 20 includes a receiving antenna positioned inside container

10 and circuitry both for decoding any electromagnetic waves detected by the antenna and for processing a received signal, if any, to determine if a breach in the integrity of the container has occurred. Receiver 20 is preferably tuned to receive a signal having frequency f₀. Receiver 20, in many embodiments, is intended to be a stand-alone, battery-powered device, but it may also be line-powered. In alternative embodiments, the antenna of receiver 20 may be located outside container 10, while the antennas of transmitters 18 are located inside container 10.

As a Faraday cage, walls 16 of container 10 will block most, if not all, electromagnetic radiation from entering or leaving container 10. Thus, if container 10 were a perfect Faraday cage, the detection by receiver 20 of any signal other than background noise would be indicative of the existence of breach 14.

However, it is rare for container 10 to be a perfect Faraday cage.

That is, container 10 is likely to have ventilation or other small holes cut into walls 16 and/or leaky seals around door 17 through which electromagnetic radiation can pass. Thus, it is expected that some electromagnetic radiation will traversewalls 16 of container 10. Nonetheless, unless breach 14 exists in walls 16, receiver 20 with its antenna located inside container 10 should not detect the presence of a strong signal being transmitted by transmitters

18. That is, the receipt by receiver 20 of a strong signal from transmitters 20 is indicative of the existence of breach 14 in the integrity of container 10.

One way to account for container 10 being an imperfect Faraday container is to monitor the received signal, if any, to determine if measured power of the received signal exceeds a threshold power level. This threshold power may be determined as a function of a power of a signal received by receiver 20 sometime after container 10 has been sealed but prior to the occurrence of breach 14. For example, upon initializing security system 12, receiver 20 may record many readings of the power of the received signal. Receiver 20 may then determine both an average and a standard deviation of the received power. In this example, the threshold power may be determined as the average power plus a multiple (perhaps

3.5 or greater) of the standard deviation. In other embodiments, the threshold power may be determined as a value independent of container 10.

The minimum size of breach 14 that can be detected using security system 12 is inversely-related to frequency f₀ as follows:

where d is the diameter of breach 14 and c is the speed of light. Essentially, a transmitted signal cannot pass through a hole smaller than its wavelength. Thus, small breaches 14 cannot be detected with low frequency signals. But, for microwave frequencies, breaches 14 having a diameter of only a few centimeters can be detected.

In some embodiments, the signal transmitted by transmitters 18 is a single frequency signal (i.e., a pure tone). In other embodiments, the signal may be modulated by a signature waveform, perhaps one conveying an absolute location of transmitter 18. In this embodiment, any signal received by receiver 20 is filtered with an analog or digital matched filter. This arrangement makes it easier to detect the presence of the signal where there is strong external interference of a narrowband type.

Although the embodiment of FIG. 1 includes three transmitters 18 and a single receiver 20, it is contemplated that any number of transmitters 18 and receivers 20 may be used. For instance, where the contents of container 10 include metal objects that may block the propagation of electromagnetic waves throughout the entire interior of container 10, it may be beneficial to use multiple receivers 20 because a single receiver 20 may not be able to detect breach 14 of container 10 if a metallic object resides between it and breach 14. The use of multiple receivers 20 helps to overcome this problem by ensuring that at least one of receivers 20 can detect breach 14. Likewise a single transmitter 18 may not be sufficient if breach 14 occurs on a side of container 10 opposite transmitter 18.

Where multiple transmitters 18 are used, transmitters 18 may cooperate to produce a time-shared broadcast to enable receiver 20 to approximate a location of breach 14. In such a scenario, transmitters 18 take turns broadcasting a signal. Based upon which transmitter 18 is transmitting at the time receiver 20 detects the signal, receiver 20 may be able to isolate a location of breach 14.

Upon detecting a signal indicative of the existence of breach 14, receiver 20 may cause an alarm to be generated. The generation of alarms is well known in the field of security. In producing an alarm, security system 12 has numerous options. In a simple example, receiver 20 may set a flag indicative of the occurrence of breach 14, which a separate device (not illustrated) connected thereto may process to alert the appropriate persons. For instance, a transmitting device may be mounted on an outside surface of container 10, and wired through walls 16 of container 10 for transmitting an alarm signal to the authorities. The alarm signal may be transmitted via any transmission protocol, including satellite, radio frequency, and hardwired transmission. For instance, where container 10 is a cargo container in ocean-transit, satellite transmission of the alarm signal may be preferred. Where container 10 is a bank vault, a hard-wired transmission may be most appropriate.

Security system 10 may continuously monitor for the occurrence of breach 14. Alternatively, security system 10 may only periodically or intermittently check for breach 14. For instance, security system may control transmitters 18 and receiver 20 to briefly attempt communication only once a minute. By only periodically checking for breach 14, security system 12 conserves energy and, where transmitters 18 and/or receiver 20 is battery- powered, prolongs the life of security system 12.

Security system 12 involves a number of components located outside of container 10. To protect these external components from tampering (e.g., external transmitters 18 being covered with a metal box or a metallic foil, or simply being removed or destroyed), external transmitters 18 may, in some embodiments, double as receivers. For example, transmitter 18a positioned in line of sight of transmitter 18b would be able to detect the signal being transmitted by transmitter 18b, such that the failure of transmitter 18a to receive the signal being transmitted by transmitter 18b is likely indicative of either a mechanical failure of security system 12 or of tampering with external transmitters 18.

The integrity of security system 12 can also be improved by transmission of a reference signal from transmitters 18 to receiver 20 via a transmission line (not shown in FIG. 1 ) hardwired between transmitters 18 and receiver 20. Failure to receive this reference signal by internal receiver 20 would then be indicative of tampering with and/or mechanical failure of transmitters 18. In this embodiment, receiver 20 may cause an alarm to be generated upon failure to receive the reference signal.

The transmission line between transmitters 18 and receiver 20 may additionally be used to enhance the sensitivity of security system 12. Specifically, if transmitters 18 were to transmit a reference signal via the transmission line that duplicates the signal transmitted to the antennas of transmitters 18, receiver 20 could evaluate not only the power but also the phase of the received signal. In other words, a transfer function from transmitter 18 to receiver 20 can be determined over some frequency range. Receiver 20 then compares the phase of the received wireless signal with that of received reference signal. Consideration of both amplitude and phase information makes the system more sensitive. Sensitivity can be further increased by broadening the frequency band of the signal. FIG. 2 is a schematic drawing of container 30 along with security system 32 for use in detecting security breach 34 in the integrity of container 30. Container 30, like container 10 of FIG. 1 , is essentially a Faraday cage having walls 36 and door 38. As shown in FIG. 2, security breach 34 is a hole in door 38 of container 30; however, other detectable security breaches 34 are possible. Security system 32 includes a plurality of security devices 40 positioned in corners of container 30. In alternative embodiments, various numbers of security devices 40 may be used and positioned anywhere along walls 36 of container 30.

FIG. 3 is a block diagram of one of the plurality of security devices 40 of FIG. 2. Security device 40 includes transmitting antennas 42a, 42b, and 42c (collectively transmitting antennas 42), receiving antenna 44, switches 46a and 46b (jointly switches 46), and mote 48.

Transmitting antennas 42 are connected to mote 48 via switch 46a, while receiving antenna 44 is connected to mote 48 via switch 46b. In this embodiment, transmitting antennas 42 are positioned outside of container 30 on a surface of walls 36, while receiving antenna 44 is positioned inside container 30. In alternative embodiments, transmitting antennas 42 and receiving antenna 44 may be oppositely positioned with transmitting antennas 42 located inside container 30 and receiving antenna 44 located outside of container 30. Additionally, security device 40 may include various numbers of transmitting antennas 42 and receiving antenna(s) 44. For instance, security device 40 may include a single transmitting antenna 42 and a single receiving antenna 44, or three receiving antennas 44 and two transmitting antennas 42.

As shown in FIG. 3, security device 40 operates as either a transmitter or a receiver, depending upon the status of switches 46. Specifically, security device 40 is caused to function as a transmitter by activating switch 46a to connect transmitting antennas 42 to mote 48. Similarly, security device 40 is caused to function as a receiver by activating switch 46b to connect receiving antenna 44 to mote 48.

Mote 48 is a device containing a microprocessor and a transceiver. When operating as a transmitter, the transceiver of mote 48 both generates a signal having frequency f₀ and transmits that signal to transmitting antennas 42 for radiation as electromagnetic waves. When operating as a receiver, the transceiver of mote 48 both decodes a received signal and calculates the power of that signal, while the microprocessor of mote 48 keeps track of the power of the received signal, optionally performs some averaging of the power of the signal over time, and produces an alarm if breach 34 is detected. Other configurations of mote 48 are possible. The embodiment of FIGS. 2 and 3 allows for a single processor (or mote) 48 to operate as for both a transmitter and a receiver, in lieu of separate processors for each transmitter and receiver of security system 12 of in FIG. 1. In one embodiment, security devices 40 operate in a "round-robin" manner in which each security device 40 takes turns functioning as a transmitter while the remaining security devices 40 function as a receiver. Otherwise, security devices 40 operate in a manner similar to security device 12 of FIG. 1. If any of security devices 40, when functioning as a receiver, detects a signal indicative of a breach, mote 48 associated with that security device 40 causes an alarm to be generated as described above.

To help detect tampering with security system 32, security device 40, when functioning as a receiver, may attempt to "hear" the transmitted signal via both its internal receiving antenna 44 and its external transmitting antenna 42. Here, failure to receive the signal via external transmitting antennas 42 would be indicative of likely tampering or mechanical failure, while receipt of the signal by internal receiving antenna 44 would be indicative of breach 34.

A possible cause of false alarms is electromagnetic radiation generated by a powerful external source, such as a cellular telephone, in use near container 10. Because container 10 is likely an imperfect Faraday cage, some of the electromagnetic radiation generated by the external source may leak into container 10, thus causing a change in the power of the signal received inside container 10. To avoid this problem, security device 40 may be operated to receive signals from both its external and internal antennas 42 and 44, such that external antenna 42 of receiving security device 40 will receive both the signals transmitted from transmitting security devices 40 and any signal generated from the external source. Receiving security device 40 can then account for any change in power due to the external source.

FIG. 4 is a graph illustrating the effectiveness of the present invention. A system was built having a receiver positioned inside a container and a transmitter outside of the container. In a number of tests (indicated by different lines in the graph), the power (in dBm) of a signal received from the transmitter by the receiver was plotted as a function of time as the conditions in the container changed. In each test, the results verify the effectiveness of the present invention. At time periods 60a, 60b, and 60c, the container had not been breached. Because the container is not a perfect Faraday cage (likely due to small cracks around the door and ventilation holes), the power of the signal detected by the receiver is very low. At time periods 62a and 62b, the container had been breached by a hole in the container walls. As shown in FIG. 4, this breach caused an increase of about 10% in the power of the received signal. At time period 64, the container was breached by opening the container door. Again, the power of the signal during the breach of the container is substantially greater than the power of the signal when no breach exists. In sum, the present invention introduces a novel system and method for detecting a breach in the integrity of a container having characteristics of a Faraday cage, such as a cargo container or a bank vault. At least one transmitter and at least one receiver are positioned oppositely inside and outside of the container. The transmitter transmits a signal while the receiver tries to detect the signal. Because the container is essentially a Faraday cage, the receiver will only detect the signal if a breach in the integrity of the container has occurred, allowing the radiation emitted by the transmitter to pass through the container walls to the receiver. In this way, the integrity of the container can be monitored and breaches detected. The system is of low cost due a simple apparatus and algorithm, which is based on off-the-shelf products. The system has low operation and maintenance cost due to the fact that no mechanical elements and no optical/fragile elements are employed. Finally, the performance of the system is independent of the contents of the container.

Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.

Claims

CLAIMS:

1. A system for detecting a breach in integrity of a container, the system comprising: a transmitter comprising a transmitting antenna for transmitting a wireless signal; a first receiver comprising a receiving antenna, wherein one of the transmitting and receiving antennas is positioned outside of the container and the other of the transmitting and receiving antennas is positioned inside the container; and a detection circuit that detects whether a wireless signal received by the first receiver is indicative of a breach in the integrity of the container.

2. The system of claim 1 wherein the transmitting antenna is positioned outside of the container and the receiving antenna is positioned inside the container.

3. The system of claim 2 and further comprising a second receiver, the second receiver comprising a receiving antenna positioned outside of the container and a processor for evaluating a signal received by the receiving antenna of the second receiver to detect at least one of tampering with or mechanical failure of the transmitter.

4 The system of claim 2 and further comprising a second receiver, the second receiver comprising a receiving antenna positioned outside of the container and a processor for evaluating the signal received by the receiving antenna of the second receiver to determine presence of an external source of electromagnetic radiation.

5. The system of claim 1 and further comprising: a transmission line connected between the transmitter and the receiver for transmission of a reference signal from the transmitter to the receiver.

6. The system of claim 5 wherein the reference signal is a substantial duplicate of the wireless signal, and wherein the detection circuit compares a phase of the reference signal to a phase of the wireless signal.

7. The system of claim 1 wherein the wireless signal received by the receiver is determined to be indicative of a breach in the integrity of the container when power of the wireless signal exceeds a threshold power of the wireless signal.

8. The system of claim 1 wherein the wireless signal is one of a radio frequency signal or a microwave frequency signal.

9. The system of claim 1 wherein the wireless signal is modulated by a signature signal.

10. The system of claim 1 wherein the container is one of a cargo container or a security vault.

11. A system for detecting a breach in integrity of a container, the system comprising a plurality of devices each comprising: a transmitting antenna; a receiving antenna, wherein one of the transmitting and receiving antennas is positioned outside of the container and the other of the transmitting and receiving antennas is positioned inside the container; and a transceiver coupled to the transmitting and receiving antennas, the transceiver capable of transmitting a signal to the transmitting antenna for radiation as electromagnetic waves, the transceiver further capable of decoding a signal received by the receiving antenna and evaluating the received signal to determines if the received signal is indicative of a breach in the integrity of the container; wherein the transceiver of at least one but not all of the devices transmits a signal while the transceivers of the remaining devices receive a signal.

12. The system of claim 11 wherein the transmitting antenna of each device is positioned outside of the container and the receiving antenna of each device is positioned inside the container.

13. The system of claim 12 wherein at least one of the receiving devices is further capable of decoding an external signal received by its transmitting antenna and evaluating the external signal to detect at least one of tampering with or mechanical failure of the transmitter.

14. The system of claim 12 wherein at least one of the receiving devices is further capable of decoding an external signal received by its transmitting antenna and evaluating the external signal to detect presence of an external source of electromagnetic radiation.

15. The device of claim 11 wherein the signal received by the receiver is determined to be indicative of a breach in the integrity of the container when a power of the signal exceeds a threshold power of the signal.

16. A method for detecting a breach in integrity of a container, the method comprising: radiating electromagnetic waves from an transmitting antenna; monitoring a signal received from a first receiving antenna, wherein one of the transmitting and first receiving antennas is positioned outside of the container and the other of the transmitting and first receiving antennas is positioned inside the container; and detecting that a breach in the integrity of the container has occurred as a function of a power of the received signal.

17. The method of claim 16 wherein detecting that a breach in the integrity of the container has occurred as a function of the power of the received signal comprises: detecting that a power of the received signal exceeds a threshold power of the received signal.

18. The method of claim 16 periodically implemented.

19. The method of claim 16 wherein the transmitting antenna is positioned outside of the container and the first receiving antenna is positioned inside the container, the method further comprising: monitoring a signal received from a second receiving antenna positioned outside of the container to detect at least one of tampering with or mechanical failure of the transmitter.

20. The method of claim 16 wherein the transmitting antenna is positioned outside of the container and the first receiving antenna is positioned inside the container, the method further comprising: monitoring a signal received from a second receiving antenna positioned outside of the container to detect presence of an external source of electromagnetic radiation.