System and method for locating radio frequency identification tags

A security system, comprising:

• a controller;
• at least one card reader in data communication with said controller, said at least one card reader configured for reading data from security cards;
• and
• a plurality of transponder readers disposed at fixed locations in a building, wherein said transponder readers are in data communication with said controller, wherein the transponder readers can estimate the positions of a plurality of moveable transponders relative to said transponder readers, said positions and said data read from said security cards being used to control access to a given location;
• wherein at least one of said moveable transponders comprises a processor executing a program configured for analyzing said radio frequency signals transmitted by said transponder readers and deriving an estimate of the position of said at least one moveable transponder in relation to each of said transponder readers.

A security system, comprising:

• means for transmitting electromagnetic radiation having data associated therewith, said means for transmitting disposed at a fixed position in a building;
• means for receiving said electromagnetic energy and data transmitted by said means for transmitting, said means for receiving being portable;
• means for controlling said means for transmitting, said means for controlling being operatively coupled thereto;
• means for reading information from a security device, said means for reading being in data communication with said means for controlling;
• and
• means for processing, said means for processing having a computer program associated therewith and being operatively coupled to said means for receiving, said means for processing and said computer program cooperating to process said data so as to determine the position of said means for receiving with respect to said means for transmitting;
• wherein said means for controlling utilizes said position and said information in order to control access.

A method of controlling access at a security perimeter of a building, comprising:

• disposing a reader in proximity to said security perimeter of said building, said reader being capable of reading information from a first portable device;
• reading information from said first portable device using said reader;
• disposing a plurality of transceivers each having a plurality of antenna coils in proximity to said security perimeter of said building, said transceivers being capable of radiating electromagnetic energy;
• providing a controller in data communication with said reader and said plurality of transceivers;
• radiating said electromagnetic energy from each of said plurality of transceivers;
• transporting a second portable device within range of i at least a portion of said plurality of transceivers, said second portable device being capable of receiving said electromagnetic energy and determining its position relative to said transceivers based thereon;
• analyzing said electromagnetic energy using said second portable device and generating data relating to the position thereof;
• transmitting said position data from said second portable device to at least one of said transceivers;
• analyzing said position data and said information read by said reader;
• and
• controlling access through said security perimeter of said building based on said act of analyzing.

A method of controlling access at a security perimeter of a building, comprising:

• obtaining identification information from a first portable device using a reader disposed at a fixed location in proximity to said perimeter;
• radiating radio frequency signals of different phase to a second portable device;
• deriving an estimate of the position of said second portable device based on said radio frequency signals, wherein said deriving is performed within said second portable device;
• transmitting said estimate of position to a controller which controls access;
• transmitting said identification information to said controller;
• and
• a controlling access at said perimeter based on said identification information and said estimate of position.