Dual mode transmitter/receiver and decoder for RF transponder tags
First Claim
1. A method for interrogating a backscatter generating tag, comprising the steps of:
- (a) generating an interrogation signal having a frequency within an interrogation band;
(b) emitting the interrogation signal as a radio wave signal;
(c) interacting the emitted radio wave signal with a backscatter generating tag;
(d) receiving a radio frequency backscatter signal from the tag;
(e) mixing the received backscatter signal with a plurality of differing phase representations of the interrogation signal to produce a plurality of mixed signals;
(f) comparing a respective signal strength of said plurality of mixed signals; and
(g) analyzing said difference signals over time to determine a significant information sequence of the backscatter signal, while discounting an importance of at least one of the plurality of mixed signals at any given time based on said compared respective signal strengths.
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Accused Products
Abstract
An enhanced backscatter RF-ID tag reader system and multiprotocol RF tag reader system is provided. In a multiprotocol mode, the system emits a non-stationary interrogation signal, and decodes a phase modulated backscatter signal by detecting a stronger phase component from quadrature phase representations or determining phase transition edges in a phase of a received signal. The RF tag reader system predicts or follows the phase of the backscatter signal, thereby avoiding interference from nulls in the received signal waveform due to the non-stationary interrogation signal, relative movement or environmental effects. An acoustic RF-ID tag detection system detects the reradiated signal corresponding to respective transformation of a signal in the tag. Detection of either type of RF-ID tags therefore is possible, and the absence of any tag or absence of any valid tag also determined.
363 Citations
55 Claims
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1. A method for interrogating a backscatter generating tag, comprising the steps of:
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(a) generating an interrogation signal having a frequency within an interrogation band; (b) emitting the interrogation signal as a radio wave signal; (c) interacting the emitted radio wave signal with a backscatter generating tag; (d) receiving a radio frequency backscatter signal from the tag; (e) mixing the received backscatter signal with a plurality of differing phase representations of the interrogation signal to produce a plurality of mixed signals; (f) comparing a respective signal strength of said plurality of mixed signals; and (g) analyzing said difference signals over time to determine a significant information sequence of the backscatter signal, while discounting an importance of at least one of the plurality of mixed signals at any given time based on said compared respective signal strengths. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A transponder interrogation system for interrogating a transponder which receives a radio frequency wave and emits a modified radio frequency wave, comprising an interrogation radio frequency wave generator, generating a radio frequency excitation pulse having a plurality of different frequencies within a frequency range for communicating with the transponder;
- an antenna, for receiving the modified radio frequency wave;
a first decoder, for determining the plurality of characteristic time-delays represented in the modified radio frequency wave; and
a second decoder for determining a sequence of modulation states from the modified radio frequency wave.
- an antenna, for receiving the modified radio frequency wave;
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18. A backscatter transponder interrogation system, comprising:
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(a) an input for receiving a backscatter signal from a backscatter transponder due to an interrogation signal; (b) a multiphase mixer for mixing said received backscatter signal and a representation of said interrogation signal to produce a plurality of multiphasic outputs; (c) means for selecting less than all of the plurality of multiphasic outputs based on a magnitude of signal strength thereof; and (d) a decoder for decoding a sequence of symbols from the selected mixer multiphasic outputs.
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19. An RF-ID tag interrogator, responsive to a return signal from an RF-ID tag having a semiconductor device outputting symbols which are accessed serially over time to sequentially modulate an interrogation signal at a modulation rate, comprising:
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a transmitter for transmitting a radio frequency interrogation signal, said interrogation signal having a frequency which substantially varies over time; a receiver for receiving a signal from the RF-ID tag which corresponds to said radio frequency interrogation signal, sequentially modulated over time based on the symbols during a period in which said interrogation signal frequency substantially varies; a decoder, having; a phase-sensitive demodulator for extracting a complex modulation pattern from said received signal, with respect to a representation of said interrogation signal; a symbol detector for receiving said complex modulation pattern, extracting a data clock from one of said complex modulation pattern, said interrogation signal, or a reference clock, compensating for a phrase rotation in the complex modulation pattern due to frequency variation of said interrogation signal at a rate faster than the modulation rate, and extracting said symbols from said compensated complex modulation pattern and said data clock.
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20. A radio frequency receiving device, operating in an environment including an RF generator, generating a time-variant RF signal which propagates through space, and an RF signal modulator having a frequency modulation pattern based on data symbols stored in said device, comprising:
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an input for receiving a frequency modulated signal corresponding to said time-variant RF signal modulated by the data symbols; a demodulator for producing a demodulated signal by mixing a signal corresponding to said time-variant RF signal with said received signal, while preserving a phase pattern; a comparator for selecting a phase component having a greatest magnitude from at least two phase components having differing phase axes of said demodulated signal, said comparator having a magnitude selectivity pattern excluding selection of a component based primarily on a pattern of said data symbols; a detector for detecting an amplitude or relative phase change of said selected phase component to extract said data symbols; and an output for outputting information relating to said data symbols.
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21. A device for receiving information from a remote tag, the tag having information stored in a memory and a modulator for frequency modulating an incident signal based on the stored information, comprising:
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a transmitter for transmitting a radio frequency carrier having a time varying center frequency in proximity to the tag; a receiver for receiving a frequency modulated, time varying center frequency carrier signal from the tag; a balanced mixer for receiving said frequency modulated, time varying center frequency carrier signal and said radio frequency carrier to produce at least a difference signal with at least two outputs each representing a different phase axis; and a detector circuit for receiving said at least two outputs and extracting the information from at least one of said outputs, the information being extracted during a period in which said radio frequency carrier center frequency varies.
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22. A radio frequency receiving device, operating in an environment including an RF generator, generating a phase-continuous, time-variant RF signal which propagates through space, and an RF signal modulator having a frequency modulation based on data symbols, comprising:
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an input for receiving a frequency modulated signal corresponding to said time-variant RF signal modulated by the data symbols; a demodulator for producing a demodulated signal by mixing a signal corresponding to said time-variant RF signal with said received signal, while preserving a phase pattern; a comparator for selecting a phase component having a greatest magnitude from at least two phase components having differing phase axes of said demodulated signal wherein said comparator has a magnitude selectivity pattern excluding selection of a component based primarily on a pattern of said data symbols; a detector for detecting an amplitude or relative phase said selected phase component to extract said data symbols; and an output for outputting information relating to said data symbols.
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23. An RF-ID tag reader, responsive a return signal from an RF-ID tag having an RF output modulating an interrogation signal over time in a pattern corresponding to a sequence of symbols, comprising:
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a receiver for receiving a modulated signal from the RF-ID tag which corresponds to said radio frequency interrogation signal, modulated over time based on the symbols; a complex demodulator for demodulating in complex space a modulated signal pattern of the received modulated signal to produce at least two phases and selectively producing an output based on a phase having a greater signal strength, to extract a modulation pattern from said demodulated signal; and an analyzer for reconstructing the symbols from the detected modulation pattern. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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- 34. A dual mode tag identification system, comprising means for emitting a time-varying radio frequency interrogation signal and means for receiving a reradiated modified representation of the interrogation signal, the reradiated modified representation of the interrogation signal being analyzed in a first mode to determine a predetermined identifying transfer function for said interrogation signal and in a second mode to determine a time sequence of modulation states imposed on said interrogation signal.
Specification