System for detecting radio-frequency identification tags
First Claim
1. A system comprising:
- a plurality of radio frequency (RF) antennas set up to provide an interrogation corridor;
a RF reader coupled to the plurality of antennas, the RF reader having a single transmitter/receiver (T/R) port that provides each of the antennas with RF power to produce interrogation fields within the interrogation corridor and delivers a combined input signal to the RF reader, wherein the RF reader generates a tag detection signal to indicate that at least one tag is present within the interrogation corridor;
a splitter that receives the RF power from the RF reader and delivers the RF power to each of the plurality of antennas in the form of a plurality of antenna drive signals, wherein the splitter receives one or more input signals from the plurality of antennas and combines the one or more tag signals to form the combined input signal;
a sensor to detect a patron within the interrogation corridor and generate a patron signal; and
a controller that outputs an alarm signal upon receiving the tag detection signal and the patron signal within a time period.
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Abstract
Techniques for detecting radio-frequency identification (RFID) tags are disclosed. For example, an exit control system is described that detects unauthorized removal of articles from a protected facility. A series of antennas are setup to produce interrogation corridors located near the exit of the protected area. RFID tags are attached to the articles to be protected. Each tag includes information that uniquely identifies the article to which it is affixed and status information as to whether the articles removal from the facility is authorized. The RF reader outputs RF signals through the antennas to create electromagnetic fields within the interrogation corridors. The reader outputs RF power from a single port to the multiple antennas via a splitter/combiner. In this way, a single RF reader with only one transmitter/receiver port simultaneously interrogates multiple antennas. A variety of techniques are described by which the reader can detect the removal of an unauthorized article.
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Citations
14 Claims
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1. A system comprising:
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a plurality of radio frequency (RF) antennas set up to provide an interrogation corridor; a RF reader coupled to the plurality of antennas, the RF reader having a single transmitter/receiver (T/R) port that provides each of the antennas with RF power to produce interrogation fields within the interrogation corridor and delivers a combined input signal to the RF reader, wherein the RF reader generates a tag detection signal to indicate that at least one tag is present within the interrogation corridor; a splitter that receives the RF power from the RF reader and delivers the RF power to each of the plurality of antennas in the form of a plurality of antenna drive signals, wherein the splitter receives one or more input signals from the plurality of antennas and combines the one or more tag signals to form the combined input signal; a sensor to detect a patron within the interrogation corridor and generate a patron signal; and a controller that outputs an alarm signal upon receiving the tag detection signal and the patron signal within a time period. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method comprising:
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producing a radio frequency (RF) output signal from a single transmitter/receiver (T/R) port of an RF reader; splitting the RF output signal using a splitter into a plurality of antenna drive signals; delivering the antenna drive signals to a plurality of antennas to produce interrogation fields within an interrogation corridor, wherein each antenna receives RF power from the RF reader that is out of phase with its neighboring antennas to produce rotating interrogation fields within the interrogation corridor; generating one or more input signals with the antennas in response to at least one tag present within the interrogation fields; combining the input signals into a combined input signal using the splitter such that a weak input signal from one of the antennas is combined with a weak input signal from at least one other antenna to increase the likelihood of detecting a tag in the corridor; providing the combined input signal to the T/R port of the RF reader; outputting the tag detection signal from the RF reader to a controller; receiving a patron signal that indicates whether a patron is present within the interrogation corridor; and outputting the alarm signal upon receiving the tag detection signal and the patron signal within a time period. - View Dependent Claims (10, 11, 12, 13, 14)
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Specification