RFID Communication System and Method of Operation

Abstract

A radio frequency identification (RFID) system enabling backscatter communication between a reader and a tag. A baseband data signal is encoded, and it may be selectively inverted and used to modulate a carrier using amplitude modulation, phase modulation, or both amplitude and phase modulation. A reply received from the tag in response to a command from the reader may include an identification code associated with an object to which the tag is affixed.

Description

RELATED PATENT DATA[0001]This patent is a continuation of U.S. patent application Ser. No. 09 / 961,113, filed Sep. 20, 2001, entitled “Backscatter Interrogators, Communication Systems and Backscatter Communication Methods,” naming David K. Ovard and Roy Greeff as inventors, which is a continuation of U.S. patent application Ser. No. 09 / 066,610 (now U.S. Pat. No. 6,459,726), filed Apr. 24, 1998; the disclosures of which are incorporated herein by reference.TECHNICAL FIELD[0002]The present invention relates to backscatter interrogators, communication systems and backscatter communication methods.BACKGROUND OF THE INVENTION[0003]Backscatter communication systems are known in the art. In a backscatter system, one transponder, such as an interrogator, sends out a command to a remote communications device. After the interrogator transmits the command, and is expecting a response, the interrogator switches to a CW mode (continuous wave mode). In the continuous wave mode, the interrogator do...

AI Technical Summary

Benefits of technology

[0012]One aspect of the invention provides a backscatter interrogator. The backscatter interrogator includes a data path configured to communicate a data signal and a signal generator configured to generate a carrier signal. The carrier signal comprises a microwave signal in preferred embodiments. The interrogator also provides a modulator coupled with the data path and the signal generator. The modulator is configured to spread the data signal to define a spread data signal and amplitude modulate the carrier signal using the spread data signal. The modulator is further configured to phase modulate the carrier signal to reduce the power within the carrier signal.

Problems solved by technology

However, such identification systems are only capable of operation over a relatively short range, limited by the size of a magnetic field used to supply power to the devices and to communicate with the devices.

However, drawbacks exist with the utilization of amplitude modulation techniques.

This limits the power which can be used for communicating data if AM modulation and spread spectrum techniques are utilized within the above specified frequency band.

Images