System and method for measurement of distance to a tag by a modulated backscatter RFID reader
US8188908B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Jul 21, 2010 |
| Grant date | May 29, 2012 |
| Priority date | — |
| Expiry date | Jul 28, 2030 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01S13/84
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Distance to a modulated backscatter tag is measured with a RFID reader that measures changes in phase with frequency of modulated backscattered RF signals. Measured distances are linked to a specific tag. The effects of other sources of reflected and interfering signals are mitigated. The techniques eliminate the need for high RF bandwidth used in time-of-flight methods, and may be used with linear, limiting or other types of amplifiers in the reader receiver. Unambiguous distance to a tag may be found using the derivative of phase with RF frequency of the modulated signal backscattered by a tag. The distance to a tag can be measured with an accuracy on the order of a centimeter. The techniques utilize the characteristics of cooperative backscatter tags (transponders, labels, etc.). New readers implement the techniques which may use unmodified tags.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.