Modulated backscatter sensor system

Abstract

A radio communication system includes an Interrogator for generating and transmitting a radio signal. One or more Tags contained within the radio communication system receive the radio signal. A Backscatter Modulator modulates the reflection of the radio signal using a subcarrier signal, thereby forming a reflected modulated signal. The Interrogator receives and demodulates the reflected modulated signal. Based upon the characteristics of the demodulated signal, the Interrogator can determine the identity of the Tag, and the relative velocity of the Tag with respect to the Interrogator. The Interrogator can also determine if motion exists in the vicinity of the Interrogator, even when no Tag is present, without the need for a separate motion detection system. The characteristics of the demodulated signal, can also be used to determine the characteristics of motion of the Tag, such as the vibrational frequency. Alternate embodiments allow the Interrogator to transmit a first information signal to one or more tags, specifying which Tags should respond using Modulated Backscatter, so that the characteristics of only particular Tags can be determined. Further alternate embodiments allow the Tag to input analog data, and perform analog to digital conversion of that data. This data may be then transmitted to the Interrogator using Modulated Backscatter. Alternately, this data may be used as input to calculations performed in the Tag in order to analyze the frequency characteristics of the analog input. The Tag can also, based upon the results of these calculations, identify an abnormal condition and notify the Interrogator of the existence of such a condition.

Dependencies are inferred from the claim text.