HK1130932A - Alarm systems, wireless alarm devices, and article security methods - Google Patents

Description

Alarm system, wireless alarm device and article protection method

Priority requirement

Priority is claimed in this application for U.S. provisional patent application No.60/796,226 entitled "Alarm Systems, Wireless Alarm Devices, And annular Security Methods", filed on 28.4.2006, the teachings of which are incorporated herein by reference.

Technical Field

The invention relates to an alarm system, a wireless alarm device and an article protection method.

Background

Theft detection electronic systems have been used in a number of applications including, for example, consumer retail applications to deter theft. Certain implementations of the theft detection electronic system may utilize wireless communication to provide protection. However, relatively low power consumption communication may be used in some configurations of these systems, which may present problems in accurate detection and communication. There may be additional problems because certain components of the theft detection electronic system may be portable and, thus, may rely on battery power in certain applications. For these particular implementations, it may be desirable to reduce power consumption to extend the useful life of battery powered components of the theft detection electronic system. Accordingly, in at least some system configurations, it is desirable to avoid the use of relatively high power consuming circuits such as amplifiers.

At least certain embodiments of the present invention describe apparatuses and methods that provide improved communications.

Drawings

Embodiments of the present invention are described below with reference to the drawings.

FIG. 1 is a schematic representation of an alarm system according to one embodiment.

Fig. 2 is a functional block diagram of a remote communication device according to one embodiment.

Fig. 3 is a functional block diagram of a conditioning circuit (conditioning circuit) of a remote communication device according to one embodiment.

Fig. 4 is a schematic diagram of conditioning circuitry of a remote communication device according to one embodiment.

Fig. 5 is a diagram showing how fig. 5a and 5b are combined. Fig. 5a and 5b are combined followed by a flow chart of a method performed by a remote communication device according to one embodiment.

Fig. 6 is a schematic diagram of a monitoring circuit (monitoring circuit) of a telecommunication device according to one embodiment.

Fig. 7 is a schematic diagram of conditioning circuitry of a remote communication device according to one embodiment.

Detailed Description

The following other U.S. patent applications are first directed: U.S. patent applications entitled "Alarm Systems, Wireless Alarm Devices, And Annis D.Belden, Jr., attorney docket, 1796153US2AP, filed on the same day as the present application, And U.S. patent applications entitled" Alarm Systems, Wireless Alarm Devices, And And Security Methods, And Annis D.Belden, Jr., attorney docket, filed on the same day as the present application, And U.S. patent applications entitled "Alarm Systems, Wireless Alarm Devices, And And Artic Security Methods, And Annis D.Belden, Jr., attorney docket, And 1796157US2AP, filed on the same day as the present application, the teachings of both of which are incorporated herein by reference.

Referring to fig. 1, an exemplary configuration of an alarm system in accordance with an exemplary embodiment of the present invention is indicated by reference numeral 10. Alarm system 10 includes a base communication device 12 and one or more remote communication devices 14 (only one device 14 is shown in fig. 1) located remotely from base communication device 12. Remote communication device 14 may be portable and mobile relative to base communication device 12 in one embodiment, and may be referred to as a wireless alarm unit in some configurations. In the described embodiment, base communication device 12 and remote communication device 14 are configured to enable wireless communication, including radio frequency communication, between each other.

In an exemplary embodiment, alarm system 10 may be used to protect a plurality of items (not shown). In a more particular example, alarm system 10 may be implemented in a consumer retail application to protect a plurality of items including consumer goods for sale. In some applications, multiple remote communication devices 14 may be used to secure multiple items, respectively. The remote communication devices 14 may each be associated with an item, for example, in one embodiment, by attaching the remote communication devices 14 to the item to be protected.

In one embodiment, the alarm system 10 may be implemented to protect an item to be retained at a given location until authorized for removal from that location. For example, the alarm system 10 may be associated with a room such as a retail store, and it may be desirable to retain an item within a defined area (e.g., inside the store), and generate an alarm if an unauthorized attempt to remove the item from the defined area is detected. One exemplary configuration of alarm system 10 for use in a retail article surveillance implementation is Electronic Article Surveillance (EAS). Alarm system 10 may implement different types of EAS monitoring in different embodiments. Examples of different configurations of EAS include AM (acousto-magnetic), EM (electromagnetic) and RF (radio frequency).

Thus, in one embodiment, base communication device 12 may be located near an access point 16 of a room. In the exemplary depicted embodiment, base communication device 12 includes a plurality of doors 18 positioned near access point 16 (e.g., doors 18 may be positioned on opposite sides of a retail store doorway). In the depicted implementation, door 18 may emit a wireless signal that defines a protected area at entry point 16 such that remote communication device 14, if brought into or removed from the defined area corresponding to the interior of the store, will pass through the protected area (e.g., in FIG. 1, the defined area containing protected items may be to the right of door 18, while the left side of the door may not be protected). In one embodiment, if a single room or area has multiple entry/exit points, multiple base communication devices 12 may be used to protect the room or area.

The alarm system 10 is configured to generate an alarm in response to detecting the presence of one of the remote communication devices 14 within the protected area. As will be described further below, the protected area may correspond to the wireless communication range of door 18 of base communication device 12, and in one example described above, door 18 may be located near an access point 16 of a room containing protected items. Base communication device 12 may transmit a wireless signal corresponding to a protected area within the protected area, and remote communication devices 14 brought into the protected area receive the wireless signal and may transmit an alert signal in response to receiving the wireless signal. Accordingly, a protected area may be defined and used in one embodiment to generate an alarm when the remote communication device 14 is located in proximity to the access point 16 in one configuration (i.e., an alarm to indicate potential theft of an item is generated by bringing the item to which the remote communication device 14 is attached within communication range of the base communication device 12 corresponding to the protected area).

Referring to fig. 2, an exemplary configuration of remote communication device 14 is shown according to one embodiment. In the illustrated configuration, the remote communication device 14 includes a tag 20 coupled to an alarm device 22. A housing, such as a plastic container (e.g., corresponding to a box like that numbered 14 in fig. 2, in one embodiment), may be made to house and protect one or both of the tag 20 and/or the alarm device 22, and the housing may be used to couple, attach or otherwise associate the remote communication device 14 with an item to be protected. In an exemplary embodiment, the enclosure may encase (encase) some or all of the components of the device 14, while in other embodiments, the enclosure may be used to support (support) rather than encase the components. Any suitable housing for supporting the components of the device 14 may be used. In the exemplary depicted embodiment, the alarm device 22 includes conditioning circuitry 30, processing circuitry 32, storage circuitry 34, alarm circuitry 36, and a power source 38. In an exemplary embodiment, power source 38 may be provided in the form of a battery and coupled to provide usable electrical energy to one or more of conditioning circuitry 30, processing circuitry 32, storage circuitry 34, and/or alarm circuitry 36. In other embodiments, other alternative configurations of remote communication device 14 and alarm device 22 are possible including more, fewer, and/or alternative elements.

In the depicted embodiment, tag 20 is configured to enable wireless communication with base communication device 12. In one configuration, tag 20 includes an antenna circuit in the form of a parallel LC resonant circuit configured to resonate in response to electromagnetic energy emitted by base communication device 12 (e.g., in one embodiment, an inductance and capacitance may be connected in parallel between node R1 and ground in fig. 4). In one configuration, the inductance of the antenna circuit is a solenoidal coil (solenoid) inductance configured to resonate at the communication frequency of base communication device 12. In one embodiment, the exemplary tag 20 may comprise Electronic Article Surveillance (EAS) equipment commercially available from a number of suppliers. As will be discussed below, the remote communication device 14 may generate a human perceptible alarm signal in response to the resonance of the antenna circuit. The alarm signal may indicate that the remote communication device 14 (and associated item, if any) is within a protected area, such as at a doorway of a retail store.

Base communication device 12 is configured to emit electromagnetic energy for interacting with remote communication device 14 to effect a protective action. Base communication device 12 may ignore electromagnetic energy in the form of wireless signals having different frequencies at different times. In one configuration, base communication device 12 transmits a carrier frequency (e.g., below 55MHz) that may be frequency modulated, wherein the carrier sweeps sinusoidally over a range of frequencies from a lower frequency to a higher frequency. For example, in one possible RF EAS implementation, base communication device 12 may transmit a wireless signal in the form of an 8.2MHz carrier wave that is FM modulated to scan at a rate of 60Hz in the 8.2MHz +/-500KHz range. In another embodiment, base communication device 12 may ignore electromagnetic energy bursts (bursts) at different frequencies in the desired band of 8.2MHz +/-500 KHz. In other embodiments, communication between base communication device 12 and remote communication device 14 may occur at other frequencies (e.g., an AM EAS configuration may communicate in the range of 55-58 kHz).

Remote communication devices 14 are individually configured to resonate at a range of frequencies within the modulation frequency range of the carrier signal transmitted by base communication device 12. For example, the LC elements of tag 20 may be tuned to resonate (and correspondingly receive electromagnetic energy emitted by base communication device 12) when tag 20 is located within the protected area, and the carrier signal corresponds to the resonant frequency of tag 20. For example, in one embodiment, the resonant frequency range of the tag 20 is only a portion of the carrier frequency range (e.g., 8.2MHz +/-500KHz in one example) of the wireless signal from the device 12. Also, in one embodiment, different devices 14 may resonate at different frequency range portions of the wireless communication range of base communication device 12. In one embodiment, the resonance may be detected by base communication device 12 and may trigger base communication device 12 to generate a human perceptible alarm.

In one embodiment, the resonance of the tag 20 results in the generation of a reference signal that is transmitted to an alarm device 22 located within the remote communication device 14. The reference signal may be referred to as a first electrical signal and may include a signature (e.g., a pattern) of the alternating current energy corresponding to the carrier frequency transmitted by base communication device 12 at a time when the carrier frequency is equal to the resonant frequency of tag 20. The reference signal may be sent to conditioning circuitry 30, which may generate a pattern of a plurality of identifiable components (e.g., pulses) that each correspond to one of the bursts of AC energy. The pulses are received by processing circuitry 32, which processing circuitry 32 may analyze the pulses in an attempt to distinguish between pulses corresponding to electromagnetic energy emitted by base communication device 12 and pulses generated by other sources of electromagnetic energy, e.g., corresponding to noise or interference. Processing circuitry 32 may control alarm circuitry 36 to emit a human perceptible alarm upon detecting that device 14 receives electromagnetic energy from base communication device 12.

In one embodiment, the processing circuitry 32 is configured to process data, control data access and storage, issue commands, and control other desired operations of the remote communication device 14. Processing circuitry 32 may monitor signals corresponding to communications of base communication device 12. As discussed further below, processing circuitry 32 may analyze the pulse length and duty cycle of the pulse stream generated by conditioning circuitry 30, according to an exemplary embodiment. The processing circuit 32 may use a discrimination window method (discrimination window method) that specifies a minimum number of pulses in the detected sequence to be within a set of parameters describing the pulse switching timing (on and off). Additional details of one exemplary analysis are described in detail below. As discussed further below, the processing circuitry 32 may control the remote communication device 14 to transmit an alarm signal if the predefined parameter is met.

In at least one embodiment, the processing circuitry 32 may include circuitry configured to implement desired programming provided by an appropriate medium. For example, the processing circuitry 32 may be implemented as one or more of a processor and/or other structure configured to execute executable instructions, including, for example, software and/or firmware instructions, and/or hardware circuitry. Exemplary embodiments of processing circuitry 32 include hardware logic, PGA, FPGA, ASIC, state machines, and/or other structures alone or in combination with a processor. These examples of processing circuitry 32 are for illustration, and other configurations are possible.

The storage circuitry 34 is configured to store programming such as executable code or instructions (e.g., software and/or firmware), electronic data, databases, or other digital information, and may include a processor-usable medium. A processor-usable medium may be embodied in any computer program product or article of manufacture that can contain, store, or store programming, data, and/or digital information for use by or in connection with an instruction execution system that includes processing circuitry in the exemplary embodiment. For example, exemplary processor-usable media may include any one of physical media such as electronic, magnetic, optical, electromagnetic, infrared, or semiconductor media. Some more specific examples of processor-usable media include, but are not limited to, portable computer diskette such as a floppy disk, compact disk, hard drive, random access memory, read only memory, flash memory, cache memory, and/or other configurations capable of storing programming, data, or other digital information.

At least some embodiments or aspects described herein may be implemented using programming stored in suitable storage circuitry 34 described above or transmitted over a network or other transmission medium, configured to control suitable processing circuitry. For example, the programming can be provided via appropriate media including, for example, embodied in an article of manufacture, embodied in a data signal (e.g., a modulated carrier wave, a data packet, a digital representation, etc.) conveyed via an appropriate transmission medium, such as a communication network (e.g., the Internet and/or a private network), a wired electrical connection, an optical connection, and/or electromagnetic energy provided, for example, via a communication interface or using other appropriate communication structure or medium. In one example, exemplary programming comprising processor-usable code may be transmitted as a data signal embodied in a carrier wave.

As described above, the alarm circuit 36 may be configured to emit a human perceptible alarm signal (e.g., to notify interested parties of the fact that an item has moved into a protected area). For example, the alarm circuitry 36 may include an audible alarm and/or a visual alarm each configured to emit a human perceptible alarm signal.

Referring to fig. 3, exemplary elements of one embodiment of conditioning circuitry 30 between tag 20 and processing circuitry 32 are shown. The illustrated conditioning circuit 30 includes a detector 40, an amplifier 42, and a pulse shaper 44. Detector 40 is configured to detect the presence of wireless communications generated by base communication device 12 using the first electrical signal received by the detector. In one embodiment, detector 40 is an RF detector configured to detect relatively low power signals (millivolt levels). The detector 40 is configured to output a second electrical signal corresponding to the received first electrical signal. As described below, the detector 40 may include a non-linear detector, and the second electrical signal may have a non-linear relationship with the first electrical signal.

In the illustrated embodiment, the amplifier 42 is configured to generate a digital signal based on the AC pulse train provided by the tag 20 and using the second electrical signal output by the detector 40. The pulse shaper 44 is configured to process the output of the amplifier 42 to assist the processing circuitry 32 in detecting identifiable components (e.g., pulses) in the reference signal in the form of the second electrical signal. Additional details of the elements of fig. 3 will be discussed in the next embodiment.

Referring to fig. 4, an exemplary configuration of conditioning circuit 30 is shown. In the embodiment shown in fig. 4, an exemplary implementation of the detector 40, amplifier 42 and pulse shaper 44 is shown. In the depicted configuration, the detector 40 includes D1, L1, C4, the amplifier 42 includes a comparator U1, and the pulse shaper includes D2. The illustrated circuit provides sensitivity to signals from base communication device 12 in the millivolt range while providing a detector 40 that is passive and consumes substantially no power from power source 38. Other circuits may include more, fewer, and/or alternative components.

In the depicted embodiment, during operation, the output of tag 20, including the first electrical signal, due to resonance with electromagnetic energy is detected by a non-linear device including diode D1. More particularly, coupling capacitor C2 couples the signal generated by tag 20 to detector 40 while allowing for a DC shift (DC shift) that becomes the output signal. Diode D1 conducts forward when the RF signal received by tag 20 is negative, clamping the waveform to ground, and does not conduct when the RF signal is positive, generating (develop) a positive signal corresponding to the instantaneous peak of the RF waveform (e.g., 8.2MHz) produced by base communication device 12 for half a wave period, providing a DC or slowly varying AC waveform proportional to the amplitude of the RF signal received by tag 20. The inclusion of the non-linear element D1 in the detector 40 improves the sensitivity of the alerting device 22 of the remote communication device 14. In one embodiment, diode D1 provides a non-linear relationship in which the current through diode D1 is clamped to ground during the negative half-cycles of the received voltage corresponding to the electrical signal received from tag 20 and allowed to swing positive during the positive half-cycles, and provides an output signal to C4 that is therefore proportional to the positive peak value of the received signal. The detected DC component signal is DC coupled to C4 and AC blocked by the inductor. C4 holds the detected voltage value. Thus, in one embodiment, C4 of detector 40 is configured to produce an envelope of the signal that generally resembles a square wave consistent with the general trend of the RF envelope of the signal received from base communication device 12.

In the depicted embodiment, C3 is coupled through inductor L1 and is selected to provide a parallel resonance of the combination of elements at the frequency band transmitted by base communication device 12, thereby increasing the AC impedance of the circuit connected to tag 20. The increased impedance reduces the load on the tag 20 so that the voltage thereon is higher, thereby improving sensitivity and providing increased reflection by the antenna circuit of the tag 20 of the signal to the base communication device 12. In one embodiment, a detector 40 including a non-linear detector is provided that generates pulses having an absolute value relationship to the signal received by the antenna circuit by using a diode D1 and applies the pulses to a comparator U1. In the depicted embodiment, the detector 40 has a non-linear transfer characteristic, wherein in one embodiment, the input and output of the detector 40 have an absolute value relationship through the use of diode D1.

Detector 40 according to one embodiment described increases sensitivity to wireless communications of base communication device 12 without the use of amplifiers operating at RF frequencies that may otherwise consume significant current and significantly reduce battery life.

The reference signal output by the detector 40 is converted to logic levels by the comparator U1 and the associated elements R3, R4 and R5 of the amplifier 42. The logic level reference signal is provided to a pulse shaper 44. D2 of pulse shaper 44 removes noise from the comparator output and provides relatively clean pulses for analysis by processing circuitry 32. D2 allows for a fast fall time of the detected RF signal and a slower rise time at a specified rate set by R6 and C5, where R6 and C5 also serve to provide some degree of noise reduction.

Table a provides a table of values for an exemplary configuration of conditioning circuit 30, where conditioning circuit 30 is configured for use with tag 20, where tag 20 includes a parallel LC resonant circuit having a solenoid coil inductance of 9.7uH and a capacitance of 39 pF. Other elements may be used in other configurations and/or with other configurations of tag 20.

Component	Part name/value
		R1	3K
R2	150
		R3	2.4K
R4	5.6M
		R5	10M
R6	470K
		C2	1pF
C3	2pF
		C4	100pF
C5	1000pF
		C6	0.5pF
L1	100uH
		D1	SMS7621
D2	BAS70
		U1	LPV7215

TABLE A

Processing circuitry 32 is configured to receive the reference signal output from pulse shaper 44 and is configured to process the reference signal in the form of a second electrical signal to distinguish between a signal having a pattern or cadence (cadence) corresponding to wireless communication of base communication device 12 and other signals resulting from receipt of electromagnetic energy provided by sources other than device 12. Processing circuitry 32 may control alarm circuitry 36 to generate a human perceptible alarm in response to the discrimination indicating receipt of wireless communications corresponding to base communication device 12.

The processing circuitry 32 may utilize criteria in attempting to discriminate between the received electromagnetic energy. The criteria may be predefined, where, for example, the criteria are specified prior to receiving a wireless signal to be processed by the remote communication device 14. In one possible discrimination embodiment, processing circuitry 32 is configured to monitor the reference signal output by conditioning circuitry 30 and corresponding to communications between remote communication device 14 and base communication device 12 for the presence of a plurality of identifiable components (e.g., the identifiable components are generated by remote communication device 14 in response to receiving a wireless signal transmitted by base communication device 12). In one embodiment, the processing circuitry 32 is configured to monitor for the presence of identifiable components in the form of pulses. As will be described further below, in one embodiment, processing circuitry 32 may attempt to match the pulses of the reference signal being processed to a predefined pattern of pulses to discriminate between communications and interference from base communication device 12. Processing circuitry 32 may control alarm circuitry 36 to issue an alarm if a criterion is met, such as identifying a plurality of identifiable components (e.g., pulses) and/or identifying an identifiable component having the form of a predefined pattern. To provide positive identification of communications from base communication device 12, processing circuitry 32 may have to provide for receipt of the identifiable components and/or patterns within a predetermined time period. One, more or all of the above exemplary criteria may be used in an exemplary embodiment to discriminate between signals from base communication device 12 and spurious electromagnetic energy received by remote communication device 14.

More particularly, in one configuration, processing circuitry 32 may access values for a plurality of parameters corresponding to a given configuration of alarm system 10 (e.g., RF, AM, EM, discussed above). Processing circuitry 32 may utilize the parameter values during monitoring of the reference signal received from conditioning circuitry 30, where the parameter values specify a time-amplitude criterion to discriminate between communications and interference from base communication device 12. The parameter values may define characteristics of identifiable components (e.g., pulses) in the signal to be identified. In one particular example, the parameters may also define a pattern of identifiable components to be identified to indicate whether the communication is from base communication device 12. In one embodiment, parameter values for different types of systems may be predefined (e.g., defined before generating the reference signal to be processed). For example, values for different configurations may be preprogrammed into the remote communication device 14 prior to use of the device in the field, and an appropriate set of values may be selected corresponding to the type of alarm system 10 to be used.

Exemplary parameters for the identifiable components and/or the pattern of the identifiable components may include minimum and maximum pulse width parameters, minimum and maximum pulse gap parameters, maximum valid pulse gap, number of pulses, and number of successes. The pulse width parameter is used to define the pulse width to be monitored. The pulse gap parameter defines a minimum and a maximum length of time between adjacent pulses, the maximum valid pulse gap corresponding to a length of time that a timeout occurs if no other pulse is received in that length of time after the previous pulse. In one embodiment, processing circuitry 32 may perform a moving window analysis in which a given number of correct pulses defined by the success number parameter are attempted to be located within a moving window of pulses defined by the pulse number parameter. Further details regarding monitoring identifiable components of the pulse form in relation to the predefined pattern of pulses will be described with respect to fig. 5.

Referring to fig. 5, an exemplary method of processing a reference signal is shown according to one embodiment. The method may be attempted to be performed to discriminate between electromagnetic energy generated by base communication device 12 and received by remote communication device 14 and electromagnetic energy generated by other sources and received by remote communication device 14. In one example, the processing circuitry 32 is configured to perform the method, for example by executing sequential instructions. Other methods are possible including more, fewer, or alternative steps.

In step S10, all counters are reset. Exemplary counters include a pulse _ cnt counter corresponding to a number of pulses counted, and a success _ cnt counter corresponding to a number of pulses counted that satisfy respective parameter values.

In step S12, the width of the first pulse from the pulse shaper circuit is detected and measured.

In step S14, a pulse gap following the first pulse is measured.

In step S16, it is determined whether the gap measured in step S14 exceeds the max _ valid _ gap parameter. The parameter may correspond to a timeout. If the condition is affirmative, the process returns to step S10, where the counter is reset. If the condition is negative, the process proceeds to step S18.

In step S18, the pulse timing of the plurality of pulses output from the pulse shaper circuit may be performed. The determined pulse timing may be used to select one of the sets of parameter values to monitor. For example, different sets of values may be predefined and used for different configurations of alarm system 10. In one embodiment, once the pulse timing is determined, the pulse timing can be used to select a corresponding appropriate set of values. Also, in step S18, a pulse _ cnt counter may be incremented corresponding to the pulse detected in step S12.

In step S20, the width of the pulse detected in step S12 and the gap thereafter are calculated and compared to a set of corresponding pulse width and gap parameter values. If the measurement is negative based on the parameter values, the process continues to step S24. If the measurement is positive (i.e., a match) based on the parameter values, the process continues to step S22.

In step S22, the success _ cnt counter is incremented indicating that a pulse within the parameter value range was detected.

In step S24, the subsequent pulse width and gap are measured and the pulse _ cnt counter is incremented.

In step S26, the pulse gap is again compared to the max _ valid _ gap parameter. If the condition of step S26 is affirmative, the process returns to step S10, indicating a timeout. If the condition of step S26 is negative, the process proceeds to step S28.

In step S28, the measured pulse width and gap are compared to the selected parameter values. If the measurement is negative based on the parameter values, the process continues to step S32. If the measurement is positive based on the parameter values, the process continues to step S30.

In step S30, the success _ cnt counter is incremented indicating that a pulse within the parameter value range was detected.

In step S32, it is determined whether the desired number of pulses have been detected. In one example, the process waits until ten pulses have been detected. If the condition of step S32 is negative, the process returns to step S24. If the condition of step S32 is affirmative, the process proceeds to step S34.

At step S34, it is determined whether the desired number of successful pulses have been detected. In the example of monitoring ten pulses described above, the process may monitor that there is a condition of at least five of the ten pulses satisfying the criteria specified by the selected value at step S34. Other criteria may be used for steps S32 and S34 in other embodiments. If the condition of step S34 is negative, the process returns to step S10 and the remote communication device 14 does not generate an alarm. If the condition of step S34 is affirmative, the process proceeds to step S36.

At step S36, the process has discriminated that the electromagnetic energy received by remote communication device 14 is the electromagnetic energy transmitted by base communication device 12 and not the electromagnetic energy generated from other sources. This discrimination indicates the presence of the remote communication device 14 in the protected area and the processing circuitry 32 may control the transmission of the alarm signal.

At least some of the above-described exemplary embodiments provide the advantage of utilizing remote communication device 14 to distinguish between communications of base communication device 12 and other spurious electromagnetic energy that may be emitted from other sources. Moreover, at least one embodiment of remote communication device 14 provides relatively low signal strength signal detection, negligible impact on the performance of tag 20 in communication with base communication device 12, and relatively low power consumption.

Moreover, alarm system 10 may have improved discrimination in the presence of cellular and cordless telephones and other sources of interference that may prevent reliable detection of signals from base communication device 12 in, for example, electronic article surveillance systems. Thus, the alarm system 10 according to one embodiment has reduced susceptibility to false alarms caused by interference.

Referring to fig. 6, one possible embodiment of a monitoring circuit 50 that may be included in the remote communication device 14 is shown. In one embodiment, the monitoring circuit 50 may be coupled to the processing circuit 32. In some configurations, the monitoring circuitry 50 is configured to reduce false alarms due to the presence of spurious electromagnetic energy (e.g., electromagnetic energy not emitted by the system 10) in the environment in which the system 10 is implemented. In one configuration described below, the monitoring circuit 50 is configured to monitor for the presence of spurious electromagnetic energy and generate an output that can be used to reduce the occurrence of false alarms.

In one embodiment, the monitoring circuit 50 reduces false alarms that may be present with certain kinds of spurious electromagnetic interference. The illustrated configuration of monitoring circuitry 50 is configured to monitor for interference that may have similar characteristics (e.g., time signatures) as wireless communications generated by base communication device 12 (e.g., signatures used to identify communications of device 12) and may cause false alarms to occur with remote communication device 14. For example, the transmission frequency for a GSM telephone is approximately 850-1900MHz, which is substantially different compared to the transmission frequency of 8.2MHz in one embodiment of wireless communication for system 10. However, the signal transmitted by the GSM phone may be sufficient to induce a current through radiation that triggers an embodiment of the remote communication device 14. The trigger may be due to GSM interference being similar to a possible signature of wireless communication of base communication device 12.

In an exemplary embodiment, monitoring circuitry 50 is tuned to a frequency of spurious electromagnetic energy (e.g., GSM interference) and is not tuned to a frequency band of wireless communication of base communication device 12. For example, in the depicted embodiment, monitoring circuitry 50 is tuned to receive and demodulate spurious electromagnetic energy (e.g., GSM telephone transmissions or other high frequency interfering signals, for example) outside of the communication frequency band of base communication device 12. In one embodiment, in an arrangement of alarm system 10 that uses communications in a frequency band of approximately 8.2MHz, antenna 52 of monitoring circuit 50 may be tuned to a frequency band such as 100MHz-5 GHz.

An output node 54 of the monitoring circuit 50 may be coupled to the processing circuit 32. Processing circuitry 32 may process signals received from output node 54 corresponding to signals received from conditioning circuitry 30. Processing circuitry 32 may analyze the respective signals from circuitry 30, 50 that correspond in time to one another to determine whether the output of conditioning circuitry 30 with the appropriate signature is responsive to communications by base communication device 12 or to spurious electromagnetic energy. In this configuration, the output of monitoring circuitry 50 allows processing circuitry 32 to distinguish between electrical signals received from conditioning circuitry 30 that are caused by communications of base communication device 12 and electrical signals caused by spurious electromagnetic energy. As described below, the processing circuit 32 may perform discrimination analysis based on the output of the monitoring circuit 50.

The above-described embodiment is configured such that monitoring circuitry 50 detects possible sources of spurious electromagnetic energy that may affect the operation of alarm system 10, while rejecting normal communications by base communication device 12. In an exemplary embodiment of alarm system 10, when spurious electromagnetic energy is present that may affect the normal operation of alarm system 10, the receivers of both conditioning circuitry 32 and monitoring circuitry 50 may indicate the presence of a signal that is similar to the communications of base communication device 12 (e.g., having a signature corresponding to the communications of base communication device 12) but that is caused by the spurious electromagnetic energy. However, during communications of base communication device 12 in the normal frequency band (e.g., 8.2MHz), only conditioning circuitry 30 generates electrical signals indicating the presence of communications of base communication device 12, while monitoring circuitry 50 does not.

If the output electrical signals of the receivers of conditioning circuit 30 and monitoring circuit 50 are both active at the respective times and both have respective time signatures similar to the communications of base communication device 12, then it is indicated that spurious electromagnetic energy is present and processing circuit 32 ignores possible false alarm conditions and does not control alarm circuit 36 to generate an alarm signal. However, if the output electrical signal from monitoring circuit 50 is inactive (inactive) while the output electrical signal from conditioning circuit 30 is active at the corresponding time and has a valid signature, then a possible alarm condition is caused by a legitimate communication from base communication device 12, and processing circuit 32 may control alarm circuit 36 to transmit an alarm signal. Moreover, in the illustrated embodiment, processing circuitry 32 does not control the transmission of an alarm signal if the output electrical signal of monitoring circuitry 50 is active and the corresponding output electrical signal of conditioning circuitry 30 is inactive.

In one configuration, the antenna 52 may be implemented as a separate dedicated wire (wire) that functions as a monopole antenna tuned to the frequency range of the spurious electromagnetic energy to be monitored. Also, in the embodiment depicted in fig. 6, the monitoring circuit 50 operates similarly to the conditioning circuit 30, with the coupling capacitor C1 coupling RF energy to the non-linear detector diode D1 while allowing for DC offset so that relatively slowly varying signals (such as those generated from GSM cell phones and other unintended interferers) can pass through the diode D1. The non-linear element diode D1 generates an electrical signal proportional to the envelope of the spurious electromagnetic energy. The electrical signal is coupled to the holding capacitor C2 through an inductor L1, which inductor L1 is electrically short-circuited at low frequencies and open-circuited at high frequencies to minimize loading of the antenna signal. The value of C2 may be optimized for the expected timing sequence of spurious electromagnetic energy (if known or predictable). In one embodiment, the values of C1, C2, and L1 may be selected such that communications of base communication device 12 are substantially attenuated, while relatively high frequencies of spurious electromagnetic energy are optimized and detected. In the illustrated embodiment, monitoring circuitry 50 becomes active in response to the spurious electromagnetic energy while communications to base communication device 12 are either inactive or discarded. Thus, the output electrical signal of the monitoring circuit 50 is only representative of the spurious electromagnetic energy. The remaining elements of monitoring circuit 50 operate similarly to the respective elements of conditioning circuit 30 in the depicted exemplary embodiment.

In some embodiments, due to the nature of the unintentional incorporation of relatively very high frequencies (e.g., >100MHz), it may be simpler to develop a monitoring circuit 50 that receives relatively very high frequencies and rejects relatively strong levels of relatively low frequency 8.2MHz signals. In some embodiments, it may be more difficult to design a receiver of conditioning circuitry 30 that receives a relatively low frequency of 8.2MHz that is less susceptible to the relatively high levels of spurious electromagnetic energy that may be present (e.g., radio frequency energy of a GSM phone).

Referring to fig. 7, another possible configuration of conditioning circuitry 30 is shown, including an alternative detector circuit that has a lower frequency selectivity when connected to the tag antenna (as compared to the embodiment of fig. 4), and is therefore somewhat more sensitive to low level signals.

In the configuration shown in fig. 7, the detector 40 includes D1, R2, C4, the amplifier 42 includes a comparator U1, and the pulse shaper includes D2. The illustrated circuit provides sensitivity to signals from base communication device 12 in the millivolt range while providing a detector 40 that is passive and consumes substantially no power from power source 38. Other circuits may include more, fewer, and/or alternative components.

In the depicted embodiment, during operation, the output of tag 20, including the first electrical signal, due to resonance with electromagnetic energy is detected by a non-linear device including diode D1. More particularly, coupling capacitor C2 couples the signal generated by tag 20 to detector 40 while allowing for a DC shift (DC shift) that becomes the output signal. Diode D1 conducts forward when the RF signal received by tag 20 is negative, clamping the waveform to ground, and does not conduct when the RF signal is positive, generating a positive signal corresponding to the instantaneous peak of the RF waveform (e.g., 8.2MHz) produced by base communication device 12 within one half wave cycle, providing a DC or slowly varying AC waveform proportional to the amplitude of the RF signal received by tag 20. The inclusion of the non-linear element D1 in the detector 40 improves the sensitivity of the alerting device 22 of the remote communication device 14. In one embodiment, diode D1 provides a non-linear relationship in which the current through diode D1 is clamped to ground during the negative half-cycles of the received voltage corresponding to the electrical signal received from tag 20 and allowed to swing positive during the positive half-cycles, and provides an output signal to C4 that is therefore proportional to the positive peak value of the received signal. The detected DC component signal is coupled by R2 and AC filtered by R2 and C4. C4 holds the detected voltage value. Thus, in one embodiment, C4 of detector 40 is configured to produce an envelope of the signal that generally resembles a square wave consistent with the general trend of the RF envelope of the signal received from base communication device 12.

In one embodiment, a detector 40 including a non-linear detector is provided that generates pulses having an absolute value relationship to the signal received by the antenna circuit by using a diode D1 and applies the pulses to a comparator U1. In the depicted embodiment, the detector 40 has a non-linear transfer characteristic, wherein in one embodiment, the input and output of the detector 40 have an absolute value relationship through the use of diode D1.

Detector 40 according to one embodiment described increases sensitivity to wireless communications of base communication device 12 without the use of amplifiers operating at RF frequencies that would otherwise consume significant current and significantly reduce battery life.

The reference signal output by the detector 40 is converted to logic levels by the comparator U1 and the associated elements R3, R4 and R5 of the amplifier 42. The logic level reference signal is provided to a pulse shaper 44. D2 of pulse shaper 44 removes noise from the comparator output and provides relatively clean pulses for analysis by processing circuitry 32. D2 allows for a fast fall time of the detected RF signal and a slower rise time at a specified rate set by R6 and C5, where R6 and C5 also serve to provide some degree of noise reduction.

Table B provides a table of values for an exemplary configuration of conditioning circuit 30, where conditioning circuit 30 is configured for use with tag 20, where tag 20 includes a parallel LC resonant circuit having a solenoid coil inductance of 9.7uH and a capacitance of 39 pF. Other elements may be used in other configurations and/or with other configurations of tag 20.

Component	Part name/value
		R1	3K
R2	100K
		R3	2.4K
R4	5.6M
		R5	10M
R6	470K
		C2	1pF
C4	100pF
		C5	1000pF
C6	0.5pF
		D1	SMS7621
D2	BAS70
		U1	LPV7215

TABLE B

Consistent with the rules, the present disclosure has been described in language more or less specific to structural and methodical features. It is to be understood, however, that the disclosure is not limited to the specific features shown and described, since the means herein disclosed comprise preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the normal scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.

Moreover, aspects herein are provided to guide the structure and/or operation of exemplary embodiments of the present disclosure. Applicants believe that the described exemplary embodiments also include, disclose, and describe additional inventive aspects in addition to those explicitly disclosed herein. For example, additional inventive aspects may include fewer, more, and/or alternative features than those described in the illustrative embodiments. In more particular instances, applicants consider the present disclosure to include, disclose, and describe methods that include fewer, more, and/or alternative steps than those explicitly disclosed herein, as well as apparatus that includes fewer, more, and/or alternative structures than those explicitly disclosed herein.

Claims (40)

1. An alarm system comprising:

a base communication device configured to communicate wireless signals;

a remote communication device configured to communicate with the base communication device using the wireless signal, wherein the remote communication device is adapted to be associated with an item to be secured, and wherein the remote communication device comprises an alarm circuit;

wherein the remote communication device comprises a non-linear device configured to detect the wireless signals transmitted by the base communication device and to generate electrical signals corresponding to respective ones of the detected wireless signals; and is

Wherein the remote communication device further comprises a processing circuit coupled with the non-linear device and configured to process the electrical signal and control the alarm circuit to generate a human perceptible alarm in response to the processing.

2. The system of claim 1, wherein the base communication device is configured to transmit the wireless signal within a protected area and the non-linear device is configured to detect the wireless signal when the remote communication device is located within the protected area.

3. The system of claim 2, wherein the base communication device is positioned to transmit the wireless signal used to define the protected area at an access point of a defined area in which the item is protected.

4. The system of claim 1, wherein the nonlinear device comprises a diode.

5. The system of claim 1, wherein the electrical signal comprises a second electrical signal, and wherein the nonlinear device is configured to produce the second electrical signal having a nonlinear relationship with a respective one of a plurality of first electrical signals received by the nonlinear device, and wherein the first electrical signals correspond to respective ones of the wireless signals.

6. The system of claim 1, wherein the remote communication device comprises a detector, wherein the detector comprises the nonlinear device, and the detector is passive.

7. The system of claim 6, wherein the remote communication device comprises a power source configured to provide available electrical energy to a processing circuit, and wherein the detector is configured to detect the wireless signal without consuming electrical energy from the power source.

8. The system of claim 1, wherein the base communication device is configured to output the wireless signal having different frequencies within a first frequency range at a plurality of different times, and wherein the detector is configured to generate the electrical signal in response to the wireless signal having a frequency within a second frequency range that includes only a portion of the first frequency range.

9. The system of claim 8, wherein the remote communication device comprises an antenna circuit comprising a parallel LC resonant circuit configured to resonate at a second frequency range.

10. The system of claim 8, wherein the remote communication device comprises a detector, wherein the detector comprises the nonlinear device, and the detector further comprises a parallel LC circuit coupled to the detector and tuned to provide increased impedance at the second frequency range.

11. The system of claim 1, wherein the processing circuit is configured to identify the electrical signal as corresponding to the wireless signal transmitted by the base communication device, and wherein the processing circuit is configured to control generation of the human perceptible alarm in response to the identification.

12. The system of claim 1, wherein the base communication device is configured to transmit the wireless signal having a frequency below 55 MHz.

13. A wireless alarm device comprising:

a housing adapted to be coupled to an item to be protected;

a diode coupled with the housing, the diode configured to receive a first electrical signal corresponding to a wireless signal transmitted by a base communication device of an alarm system and to generate a second electrical signal in response to receiving the first electrical signal;

an alarm circuit coupled to the housing and configured to generate a human perceptible alarm; and

processing circuitry configured to process the second electrical signal and control the alarm circuitry to generate the human perceptible alarm in response to the processing of the second electrical signal.

14. The device of claim 13, further comprising an antenna circuit coupled to the housing and configured to generate the first electrical signal.

15. The device of claim 14, wherein the wireless signal has different frequencies within a first frequency range at different times, and wherein the antenna circuit is tuned to a second frequency range that is only a portion of the first frequency range, and the antenna circuit is configured to generate the first electrical signal in response to the wireless signal being within the second frequency range.

16. The device of claim 15, wherein the antenna circuit comprises a parallel LC resonant circuit tuned to resonate at a second frequency range.

17. The apparatus of claim 13, wherein the diode is configured to generate the second electrical signal having a non-linear relationship with the first electrical signal.

18. The apparatus of claim 13, further comprising a detector, wherein the detector comprises the diode, and the detector is passive.

19. The apparatus of claim 14, further comprising a detector, wherein the detector comprises the diode, and the detector further comprises a parallel LC circuit coupled to the diode and tuned to provide increased impedance at the second frequency range.

20. The device of claim 13, wherein the processing circuit is configured to identify the second electrical signal as corresponding to the wireless signal transmitted by the base communication device, and wherein the processing circuit is configured to control generation of the human perceptible alarm in response to the identification.

21. An article protection method comprising:

associating a remote communication device of an alarm system with an item to be secured;

transmitting a wireless signal in a protection area by using basic communication equipment of an alarm system;

moving the remote communication device and the associated item into the secured area;

receiving the wireless signal with the remote communication device located within the protected area;

generating, with the remote communication device, a first electrical signal corresponding to the wireless signal;

generating, with the remote communication device, a second electrical signal having a non-linear relationship to the first electrical signal; and

transmitting, with the remote communication device, a human perceptible alarm in response to the generation of the second electrical signal.

22. The method of claim 21, wherein the transmitting comprises: transmitting the wireless signal to define the protected area at an access point of a defined area in which the article is protected.

23. The method of claim 21, wherein said generating the first electrical signal comprises: resonating a parallel LC resonant circuit of the remote communication device with the wireless signal.

24. The method of claim 23, further comprising detecting the resonance with the base communication device, and in response to the detecting, generating another human perceptible alarm with the base communication device.

25. The method of claim 21, wherein the generating the second electrical signal comprises generating the second electrical signal with a non-linear device.

26. The method of claim 21, wherein the generating the second electrical signal comprises generating the second electrical signal with a diode.

27. The method of claim 21, wherein the generating the second electrical signal comprises generating the second electrical signal without consuming power from a power source of the remote communication device.

28. The method of claim 21, wherein the transmitting comprises transmitting a plurality of wireless signals having different frequencies over a first frequency range at different times, and wherein the generating the first electrical signal comprises generating a plurality of first electrical signals in response to the wireless signals having frequencies within a second frequency range that is only a portion of the first frequency range.

29. The method of claim 28, providing increased impedance in the remote communication device at the second frequency range.

30. The method of claim 21, further comprising identifying the wireless signal as corresponding to a communication of the base communication device, and wherein the transmitting comprises transmitting in response to the identifying.

31. An article protection method comprising:

receiving a wireless signal, including resonating an antenna circuit of a remote communication device, the resonating producing a first electrical signal;

generating, with the remote communication device, a second electrical signal in response to the generating the first electrical signal, the second electrical signal having a non-linear relationship with the first electrical signal; and

generating a human perceptible alarm in response to the generating the second electrical signal to indicate that the remote communication device and an item associated with the remote communication device are located within a protected area.

32. The method of claim 31, further comprising transmitting the wireless signal within the protected area with a base communication device of an alarm system.

33. The method of claim 32, wherein the transmitting comprises transmitting a plurality of wireless signals having a plurality of different frequencies within a first frequency range at a plurality of different times, and the resonating comprises resonating during transmission of the wireless signals having frequencies within a second frequency range that is only a portion of the first frequency range.

34. The method of claim 33, providing increased impedance at the second frequency range.

35. The method of claim 33, wherein the resonating comprises resonating with the antenna circuit, wherein the antenna circuit comprises a parallel LC resonant circuit tuned to the second frequency range.

36. The method of claim 31, wherein the generating the second electrical signal comprises generating the second electrical signal with a diode.

37. The method of claim 31, wherein the generating the second electrical signal comprises generating the second electrical signal with a non-linear device.

38. The method of claim 31, wherein the generating the second electrical signal comprises generating the second electrical signal with a passive circuit without consuming power from a power source of the telecommunication device.

39. The method of claim 31, further comprising identifying the wireless signal as a communication from a base communication device of an alarm system including the remote communication device, and wherein the generating the human perceptible alarm comprises generating the human perceptible alarm in response to the identifying.

40. The method of claim 39, wherein the identifying comprises identifying with the second electrical signal, wherein the second electrical signal has a predefined pattern of identifiable components defined prior to generating the second electrical signal.