Long range passive real time location system

A system, comprising:

• one or more exciters that transmit a power signal to at least a portion of a plurality of tags, wherein the exciters are located a distance from the tags within a range required to power the tags;
• and
• a reader that initiates transmission of the power signal by transmitting a command signal to the exciters, wherein the reader is located a greater distance from the tags than the range required to power the tags, wherein the reader is configured to:
• receive by the multiple wideband antennas, wideband signals from at least one of the tags, and associate with the wideband signals a time of arrival at each of the wideband antennas;
• and
• calculate a location of the at least one tag based on differences between the time of arrival at each of the wideband antennas.

An executable software product stored on a computer-readable medium containing program instructions for providing a long-range real-time location system in which a plurality of tags are associated with respective items, the program instructions for:

• transmitting a power signal from one or more exciters to at least a portion the tags, wherein the exciters are located a distance from the tags within a range required to power the tags;
• initiating transmission of the power signal by a reader that transmits a command signal instructing the exciters to transmit the power signal to the tags, wherein the reader is located a greater distance from the tags than the range required to power the tags;
• receiving by multiple wideband antennas on the reader, wideband signals from at least one of the tags, and associating with the wideband signals a time of arrival at each of the wideband antennas;
• and
• calculating by the reader a location of the at least one tag based on differences between the time of arrival at each of the wideband antennas.

A tag reader, comprising:

• a plurality of ultra wideband antennas that receive ultra wideband signals from tags, the ultra wideband (UWB) signals including a tag ID of a corresponding transmitting tag;
• a plurality of UWB receiver chains that receive the UWB signals as a series of impulses and processes the impulses into a timeframe and outputs a digital signal;
• a field programmable gate array (FPGA) that receives the digital signal from each of the plurality of UWB receiver chains, extracts the tag ID from each of the UWB signals, and associates the time of arrival of each of the UWB signals with the tag ID, forming a series of tag ID and time-of-arrival pairs;
• a memory that stores a location engine, tag database, and web server;
• and
• a processor that executes the location engine wherein the location engine uses the tag ID and time of arrival pairs and a distance between the UWB antennas to determine a location of each transmitting tag based on a time distance of arrival algorithm, wherein at least the tag ID and the location are stored in a tag database, and wherein the processor further executes the web server to allow outside access to the tag database over a network.

A method for providing a long-range passive real-time location system, comprising:

• sending a command signal from a reader to one or more exciters to energize a plurality of RFID tags via a short range narrowband power signal;
• in response to the tags receiving the power signal, transmitting a tag ID to the reader via a long-range ultra wideband signal;
• receiving the ultra wideband signals using multiple ultra wideband antennas on the reader;
• calculating by the reader a location of each of the tags based on a time-of-arrival of the ultra wideband signals at each of the ultra wideband antennas;
• storing the tag ID and location information from each of the ultra wideband signals in a database on the reader;
• and
• allowing outside access to the location information in the database over a network.