# US 8,542,717 B2 · Interrogator and interrogation system employing the same

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- Number: US 8,542,717 B2
- Document ID: US8542717B2
- Status: Granted
- Kind: B2
- Application number: 11/838,085
- Filed: 2007-08-13
- Published: 2012-12-13
- Granted: 2013-09-24
- Earliest claimed: 2003-03-03
- Assignees: Veroscan, Inc.
- Applicants: John P. Volpi; Logan Scott; David W. Hensley
- Inventors: John P. Volpi; Logan Scott; David W. Hensley
- Web page: https://patentgrep.com/patent/US8542717B2

## CPC

- G06K 7/10366: {the interrogation device being adapted for miscellaneous applications}
- G06K 7/0008: {General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer}
- G06K 17/00: Methods or arrangements for effecting co-operative working between equipments covered by two or more of main groups G06K1/00 - G06K15/00, e.g. automatic card files incorporating conveying and reading operations
- G06Q 10/08: Logistics, e.g. warehousing, loading or distribution; Inventory or stock management
- G06Q 10/087: Inventory or stock management, e.g. order filling, procurement or balancing against orders
- G06Q 10/0877: {by inventory control or reporting using inventory tracking or counting}
- G06K: GRAPHICAL DATA READING (image or video recognition or understanding G06V); PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
- G06Q: INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES; SYSTEMS OR METHODS SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES, NOT OTHERWISE PROVIDED FOR

## Abstract

An interrogator, methods of discerning the presence of an object, and interrogation systems employing the same. In one embodiment, the interrogation systems include multiple interrogators that communicate with a base command unit to track a location of an object. In another embodiment wherein the object is an RFID object (e.g., an object with an RFID tag), the interrogators employ signal processing techniques such as precharging the RFID object, and correlating a reference code with a reply code from the RFID object using selected techniques to increase a sensitivity of the interrogator, especially for adverse environments. In other embodiments, the interrogation systems include variations of metal instruments and sponges employed therewith. In yet another embodiment, the interrogation system includes metal interrogators capable of discerning the presence of a metal object, especially in a presence of another metal object.

## Claims

### Claim 1

A control and processing system, comprising:
a correlation subsystem configured to correlate a reference code at a first clock rate with a reply code from a radio frequency identification (RFID) object, correlate said reference code at a second clock rate with said reply code from said RFID object and provide correlation signals therefrom, said correlation subsystem being configured to correlate employing a Fast Fourier Transform and a convolution theorem, said first clock rate being an expected clock rate and said second clock rate varying therefrom; and
a decision subsystem configured to verify a presence of said RFID object as a function of said correlation signals.

### Claim 2 (depends on 1)

The control and processing system as recited in claim 1 wherein said correlation subsystem includes multiple correlators.

### Claim 3 (depends on 1)

The control and processing system as recited in claim 1 wherein said reference code is a synthetically derived reference code.

### Claim 4 (depends on 1)

The control and processing system as recited in claim 1 wherein said correlation subsystem is configured to correlate in a time domain employing an exclusive OR function.

### Claim 5 (depends on 1)

The control and processing system as recited in claim 1 wherein said correlation subsystem is configured to correlate said reference code at a third clock rate with said reply code from said RFID object and provide correlation signals therefrom, said second clock rate being slower than said first clock rate and said third clock rate being faster than said first clock rate.

### Claim 6 (depends on 1)

The control and processing system as recited in claim 1 wherein said correlation subsystem includes:
a correlator configured to correlate at least two bits of said reference code with at least two bits of said reply code to derive correlation triangles,
a correlation threshold sense configured to compare said correlation triangles to a threshold criteria to derive pulses to ascertain peaks of said correlation triangles, and
a summer configured to average a plurality of pulses from said correlation threshold sense to provide said correlation signals.

### Claim 7 (depends on 1)

The control and processing system as recited in claim 1 wherein said decision subsystem includes a threshold detector configured to compare said correlation signals to a threshold.

### Claim 8 (depends on 1)

The control and processing system as recited in claim 1 wherein said decision subsystem is configured to verify said presence of said RFID object by employing a statistical analysis on a result therefrom.

### Claim 9 (depends on 1)

The control and processing system as recited in claim 1 wherein said reference code is configured to be provided during an initialization stage of operation and said reply code is configured to be provided during a post-initialization stage of operation.

### Claim 10 (depends on 1)

The control and processing system as recited in claim 1 wherein said reference code is configured to be entered into a memory of said control and processing system.

### Claim 11

A method of verifying a presence of a radio frequency identification (RFID) object, comprising:
correlating a reference code at a first clock rate with a reply code from an RFID object, correlating said reference code at a second clock rate with said reply code from said RFID object and providing correlation signals therefrom, said correlating employing a Fast Fourier Transform and a convolution theorem, said first clock rate being an expected clock rate and said second clock rate varying therefrom; and
verifying a presence of said RFID object as a function of said correlation signals.

### Claim 12 (depends on 11)

The method as recited in claim 11 wherein said correlating is performed with multiple correlators.

### Claim 13 (depends on 11)

The method as recited in claim 11 wherein said reference code is a synthetically derived reference code.

### Claim 14 (depends on 11)

The method as recited in claim 11 wherein said correlating is performed in a time domain employing an exclusive OR function.

### Claim 15 (depends on 11)

The method as recited in claim 11 wherein said correlating includes correlating said reference code at a third clock rate with said reply code from said RFID object and providing correlation signals therefrom, said second clock rate being slower than said first clock rate and said third clock rate being faster than said first clock rate.

### Claim 16 (depends on 11)

The method as recited in claim 11 wherein said correlating includes:
correlating at least two bits of said reference code with at least two bits of said reply code to derive correlation triangles,
comparing said correlation triangles to a threshold criteria to derive pulses to ascertain a peak of said correlation triangles, and
averaging a plurality of pulses to provide said correlation signals.

### Claim 17 (depends on 11)

The method as recited in claim 11 wherein said verifying includes comparing said correlation signals to a threshold.

### Claim 18 (depends on 11)

The method as recited in claim 11 wherein said verifying employs a statistical analysis on a result therefrom.

### Claim 19 (depends on 11)

The method as recited in claim 11 wherein said reference code is configured to be provided during an initialization stage of operation and said reply code is configured to be provided during a post-initialization stage of operation.

### Claim 20 (depends on 11)

The method as recited in claim 11 further comprising entering said reference codes into a memory.

### Claim 21

An interrogation system, comprising:
a radio frequency identification (RFID) object configured to provide a reply code; and
an interrogator, including:
a correlation subsystem configured to correlate a reference code at a first clock rate with said reply code, correlate said reference code at a second clock rate with said reply code and provide correlation signals therefrom, said correlation subsystem being configured to correlate employing a Fast Fourier Transform and a convolution theorem, said first clock rate being an expected clock rate and said second clock rate varying therefrom, and
a decision subsystem configured to verify a presence of said RFID object as a function of said correlation signals.

### Claim 22 (depends on 21)

The interrogation system as recited in claim 21 wherein said correlation subsystem includes multiple correlators.

### Claim 23 (depends on 21)

The interrogation system as recited in claim 21 wherein said reference code is a synthetically derived reference code.

### Claim 24 (depends on 21)

The interrogation system as recited in claim 21 wherein said correlation subsystem is configured to correlate in a time domain employing an exclusive OR function.

### Claim 25 (depends on 21)

The interrogation system as recited in claim 21 wherein said
correlation subsystem is configured to correlate said reference code at a third clock rate with said reply code from said RFID object and provide correlation signals therefrom, said second clock rate being slower than said first clock rate and said third clock rate being faster than said first clock rate.

### Claim 26 (depends on 21)

The interrogation system as recited in claim 21 wherein said correlation subsystem includes:
a correlator configured to correlate at least two bits of said reference code with at least two bits of said reply code to derive correlation triangles,
a correlation threshold sense configured to compare said correlation triangles to a threshold criteria to derive pulses to ascertain a peak of said correlation triangles, and
a summer configured to average a plurality of pulses from said correlation threshold sense to provide said correlation signals.

### Claim 27 (depends on 21)

The interrogation system as recited in claim 21 wherein said decision subsystem includes a threshold detector configured to compare said correlation signals to a threshold.

### Claim 28 (depends on 21)

The interrogation system as recited in claim 21 wherein said decision subsystem is configured to verify said presence of said RFID object by employing a statistical analysis on a result therefrom.

### Claim 29 (depends on 21)

The interrogation system as recited in claim 21 wherein said reference code is configured to be provided during an initialization stage of operation and said reply code is configured to be provided during a post-initialization stage of operation.

### Claim 30 (depends on 21)

The interrogation system as recited in claim 21 wherein said reference code is configured to be entered into a memory of said interrogator.