Surveillance system employing a dual function floor mat radiator
First Claim
1. A surveillance system for detecting the presence in a controlled space of a miniature electromagnetic wave receptor-reradiator with signal mixing capability, comprising in combination means for propagating through said space an electromagnetic microwave signal, a source of low frequency signals, an electrode coupled to said source of low frequency signals and disposed in a capacitor structure constructed and arranged for disposition in said space along the path of travel of said receptor-reradiator through said space for direct capacitive coupling to said receptor-reradiator whenever the latter is present in said space, signal detecting means arranged to be coupled to said space for receiving signals therefrom and detecting signals related to said low frequency signals only when received as modulation on a carrier signal whose frequency bears a predetermined relationship to that of said microwave signals, and means coupled to said detecting means for providing an alarm responsive to detection of said signals that are related to said low frequency signals, characterized in that said means for propagating a microwave signal through said space comprises a microstrip antenna with a signal feed constructed and arranged to propagate said signal through said space, said microstrip antenna being disposed in association with said capacitor structure in a common structure.
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Accused Products
Abstract
A microstrip antenna is incorporated in a floor mat, the latter consisting of a conductive grid laminated to a conductive sheet with a layer of dielectric material therebetween to form a capacitor. The microstrip antenna is connected to a source of microwave energy for the purpose of radiating a microwave signal through a surveillance area. A low frequency signal is applied to the capacitor section of the mat for direct capacitive coupling through the body of a pedestrian to any surveillance tag carried thereupon.
75 Citations
15 Claims
- 1. A surveillance system for detecting the presence in a controlled space of a miniature electromagnetic wave receptor-reradiator with signal mixing capability, comprising in combination means for propagating through said space an electromagnetic microwave signal, a source of low frequency signals, an electrode coupled to said source of low frequency signals and disposed in a capacitor structure constructed and arranged for disposition in said space along the path of travel of said receptor-reradiator through said space for direct capacitive coupling to said receptor-reradiator whenever the latter is present in said space, signal detecting means arranged to be coupled to said space for receiving signals therefrom and detecting signals related to said low frequency signals only when received as modulation on a carrier signal whose frequency bears a predetermined relationship to that of said microwave signals, and means coupled to said detecting means for providing an alarm responsive to detection of said signals that are related to said low frequency signals, characterized in that said means for propagating a microwave signal through said space comprises a microstrip antenna with a signal feed constructed and arranged to propagate said signal through said space, said microstrip antenna being disposed in association with said capacitor structure in a common structure.
- 12. An assembly for use in a surveillance system in which the presence in a controlled space of a miniature electro-magnetic wave receptor-reradiator with signal mixing capability is detected by the combination of means for propagating through said space an electromagnetic microwave signal, a source of low frequency signals, an electrode coupled to said source of low frequency signals for disposition along the path of travel of said receptor-reradiator through said space for direct capacitive coupling to said receptor-reradiator whenever the latter is present in said space, signal detecting means arranged to be coupled to said space for receiving signals therefrom and detecting signals relating to said low frequency signals only when received as modulation on a carrier signal whose frequency bears a predetermined relationship to that of said microwave signals, and means coupled to said detecting means for providing an alarm responsive to detection of said signals that are related to said low frequency signals, said assembly being characterized by comprising in combination a conductive element and a strip conductor spaced from the margins of said element, said conductive element and said strip conductor being laminated to respective ground plane conductive layers with a layer of dielectric materials therebetween, means for effecting separate electrical connections to each of said conductive components, and layers of insulating material encasing said conductive components and dielectric material and integrating the same into a unitary floor mat structure, said conductive element constituting said electrode and said strip conductor constituting a microstrip antenna for propagating said signal through said space.
Specification