초록 ▼

System for tracking mobile tags. Cell controllers with multiple antenna modules generate a carrier signal which is received by the tags. Tags shift the frequency of the carrier signal, modulate an identification code onto it, and transmit the resulting tag signal at randomized intervals. The antenna

System for tracking mobile tags. Cell controllers with multiple antenna modules generate a carrier signal which is received by the tags. Tags shift the frequency of the carrier signal, modulate an identification code onto it, and transmit the resulting tag signal at randomized intervals. The antennas receive and process the response, and determine the presence of the tags by proximity and triangulation. Distance of a tag from an antenna is calculated by measuring the round trip signal time. The cell controllers send data from the antenna to a host computer. The host computer collects the data and resolves them into positional estimates. Data are archived in a data warehouse, such as an SQL Server.

대표청구항 ▼

[ What is claimed is:] [1.] A tag for transponding a radio frequency interrogator signal, comprising:a receiver for receiving the interrogator signal at a first frequency, said receiver being enabled for receiving only at pseudo-random intervals that are independent of generation times of said first

[ What is claimed is:] [1.] A tag for transponding a radio frequency interrogator signal, comprising:a receiver for receiving the interrogator signal at a first frequency, said receiver being enabled for receiving only at pseudo-random intervals that are independent of generation times of said first frequency;a frequency mixer for generating from the received interrogator signal a radio frequency transmit signal at a second frequency;a microprocessor for generating a tag-specific data signal;a modulator for modulating the tag data signal onto the transmit signal to generate a first tag signal; anda transmitter for transmitting the first tag signal at selected times.