Dual mode modulated backscatter system

Claim 2

The radio communication system of claim 1 wherein said first modulated signal is generated using a first modulation type selected from a group including at least amplitude, phase, frequency, time-division, and code-division modulation types.

Claim 3

The radio communication system of claim 1 wherein the interrogator demodulating means includes a homodyne detector and uses said first modulated signal as the frequency source input to said detector.

Claim 4

tag for use in a radio communication system characterized by means for receiving 301-305 said first modulated signal, means for decoding 302, 304, 305 said first modulated signal to obtain said first information signal, said first information signal indicating in which of multiple response modes a receiving tag should respond, backscatter modulator means for modulating 302, 305, 307 the reflection of said first modulated signal using a second information signal whose content, data rate, or modulation is determined by said first information signal, thereby forming a reflected second modulated signal.

Claim 5

A radio communication system characterized by an interrogator 103including means for generating 200-202 a first modulated signal by modulating a first information signal onto a radio carrier signal, said first information signal indicating which of multiple response modes a receiving tag should respond, means for transmitting 203 to said at least one tag during a first time interval said first modulated signal, and transmitting said radio carrier signal during a second time interval, said at least one tag 105 including means for receiving 301-305 said first modulated signal, means for decoding 302, 304, 305 said first modulated signal to obtain said first information signal, backscatter modulator means 302, 305, 307 for modulating the reflection, during said second time interval, of said radio carrier signal using a second information signal whose content, data rate, or modulation is determined from the contents of said first information signal, thereby forming a reflected second modulated signal, said interrogator 103 further including means for receiving 206 said second modulated signal, and means for demodulating 208-210, 212 said second modulated signal, to obtain said second information signal, whose content, data rate, or modulation was determined from the contents of said first information signal.

Claim 6

The radio communication system of claim 1 or 5 wherein said first information signal indicates which of a first mode, including a data message in said second information signal, and a second mode, including an acknowledgment message in said second information signal, that said at least one tag should respond.

Claim 7

The radio communication system of claim 6 wherein said second information signal consists of a single bit of information.

Claim 8

The radio communication system of claim 7 wherein said single bit of information is communicated by the presence or absence of a single subcarrier tone backscatter modulating said radio carrier signal.

Claim 9

The radio communication system of claim 1 or 5 when said at least one tag responds in said first mode, wherein the bits of information contained within said second information signal are differentially encoded, and wherein said demodulating means demodulates the differentially encoded bits to recover the data within said second information signal.

Claim 10

The radio communication system of claim 1 or 5 when said at least one tag responds in said second mode, wherein the bits of information contained within said second information signal are differentially encoded, and wherein said demodulating means demodulates the differentially encoded bits to recover the data within said second information signal.

Claim 11

The radio communication system of claims 9 or 10, wherein said interrogator includes means for providing a retriggerable monostable multivibrator function to detect the acknowledgment message.

Claim 12

The radio communication system of claim 1 or 5 wherein said interrogator includes processor means for performing a Fourier Transform to obtain said second information signal.