Electronic article surveillance system employing time domain and/or frequency domain analysis and computerized operation
First Claim
Patent Images
1. A surveillance system for detecting the presence of articles containing magnetic markers in an interrogation zone comprising:
- transmitting means for establishing a magnetic field at a preselected frequency in the interrogation zone;
receiving means for sensing perturbations to the magnetic field in the zone and developing a signal indicative thereof, said receiving means including means for developing a signal content profile indicative of the energy levels in each of a plurality of frequency bands of said signal; and
means responsive to said signal content profile for comparing the energy levels indicated by said signal content profile for use in evaluating whether an article is present in said zone.
2 Assignments
0 Petitions
Accused Products
Abstract
A magnetic article surveillance system utilizing microcomputer control and unique time domain and frequency domain information gathering channels whose information is processed by the microcomputer via preselected time domain and frequency domain criteria.
75 Citations
38 Claims
-
1. A surveillance system for detecting the presence of articles containing magnetic markers in an interrogation zone comprising:
- transmitting means for establishing a magnetic field at a preselected frequency in the interrogation zone;
receiving means for sensing perturbations to the magnetic field in the zone and developing a signal indicative thereof, said receiving means including means for developing a signal content profile indicative of the energy levels in each of a plurality of frequency bands of said signal; and
means responsive to said signal content profile for comparing the energy levels indicated by said signal content profile for use in evaluating whether an article is present in said zone. - View Dependent Claims (2, 3, 4)
- transmitting means for establishing a magnetic field at a preselected frequency in the interrogation zone;
-
5. A surveillance system for detecting the presence of articles containing magnetic markers in an interrogation zone comprising:
- transmitting means for establishing a magnetic field at a preselected frequency in the interrogation zone;
receiving means for sensing perturbations to the magnetic field in the zone and developing a signal indicative thereof;
said receiving means including means for developing a signal content profile indicative of the energy levels in each of at least three frequency bands of said signal; and
means responsive to said signal content profile for use in evaluating whether an article is present in said zone. - View Dependent Claims (6, 7, 8)
- transmitting means for establishing a magnetic field at a preselected frequency in the interrogation zone;
-
9. A surveillance system for detecting the presence of articles containing magnetic markers in an interrogation zone comprising:
- transmitting means for establishing a magnetic field at a preselected frequency in the interrogation zone during a surveillance operation encompassing a succession of cycles of said preselected frequency;
receiving means for sensing perturbations to the magnetic field in the zone and developing a signal indicative thereof, said receiving means including;
means for developing a signal content profile comprising samples of said signal taken over each of a plurality of time frames, each said time frame being of extent equal to the time extent of a half cycle of said preselected frequency; and
means responsive to said signal content profile for evaluating the presence of an article in said zone including means for comparing during a particular time frame, one or more samples of said signal associated with that particular time frame with one or more samples of said signal associated with another time frame. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17)
- transmitting means for establishing a magnetic field at a preselected frequency in the interrogation zone during a surveillance operation encompassing a succession of cycles of said preselected frequency;
-
18. A surveillance system for detecting the presence of articles containing magnetic markers in an interrogation zone comprising:
- transmitting means for establishing a magnetic field at a preselected frequency in the interrogation zone;
receiving means for sensing the perturbations to the magnetic field in the zone and developing a signal indicative thereof, said receiving means including;
means for developing a signal content profile comprising samples of said signal;
further means for developing a further signal content profile indicative of the energy levels in each of a plurality of frequency bands of said signal; and
means responsive said signal content profile and said further signal content profile for evaluating the presence of a marker in said zone. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
- transmitting means for establishing a magnetic field at a preselected frequency in the interrogation zone;
-
29. A surveillance system for detecting the presence of articles containing magnetic markers in an interrogation zone comprising:
- transmitting means for establishing a magnetic field at a preselected frequency in the interrogation zone;
receiving means for sensing perturbations to the magnetic field in the zone and developing a signal indicative thereof ; and
means responsive to the receiving means for evaluating whether an article is present in said zone, said evaluating means comprising a microcomputer; and
an interface which is programmable and external of said microcomputer for externally communicating with said microcomputer.
- transmitting means for establishing a magnetic field at a preselected frequency in the interrogation zone;
-
30. A surveillance system for detecting the presence of articles containing magnetic markers in an interrogation zone comprising:
- transmitting means for establishing a magnetic field at a preselected frequency in the interrogating zone, said transmitting means including antenna means and means for driving said antenna;
receiving means for sensing perturbations to the magnetic field in the zone and developing a signal indicative thereof;
evaluating means responsive to said receiving means for evaluating the presence of a marker in said zone;
means for sensing the voltage and current to said antenna means;
means for comparing the phase of said voltage and current; and
means for adjusting said drive means to reduce said phase shift to zero.
- transmitting means for establishing a magnetic field at a preselected frequency in the interrogating zone, said transmitting means including antenna means and means for driving said antenna;
-
31. A receiver for use in an article surveillance system, the system detecting the presence of articles in an interrogation zone in which a magnetic field at a preselected frequency has been established and including antenna means which senses the perturbations to the magnetic field, the receiver comprising:
- means adapted to be responsive to an antenna means for producing a signal; and
means for processing said signal including comb bandpass filter means having pass bands at harmonics of said preselected frequency, said comb band pass filter comprising a digital delay line having;
a plurality of delay stages, input and output ports;
a clock port; and
feedback means coupling said input and output ports. - View Dependent Claims (32)
- means adapted to be responsive to an antenna means for producing a signal; and
-
33. A receiver for use in an article surveillance system, the system detecting the presence of articles in an interrogation zone in which a magnetic field at a preselected frequency has been established and including antenna means which senses the perturbations to the magnetic field, the system being subjected to signals of given frequency from the system power line, the receiver comprising:
- means adapted to be responsive to an antenna means for producing a first signal; and
means for processing said first signal including comb notch filter means having rejection bands at harmonics of said given frequency. - View Dependent Claims (34, 35)
- means adapted to be responsive to an antenna means for producing a first signal; and
-
36. A comb bandpass filter comprising:
- a digital delay line having;
a plurality of delay stages;
input and output ports and a clock port; and
feedback means for coupling said input and output ports. - View Dependent Claims (37)
- a digital delay line having;
-
38. A comb notch filter comprising:
- a digital delay line having;
a plurality of delay stages;
input and output ports and a clock port;
feedback means connecting said input and output ports;
a first port for receiving an input signal, said first port being coupled to said input port of said delay;
a differencing circuit having first and second inputs coupled to said first port and said input port, respectively.
- a digital delay line having;
Specification