Radio frequency identification interrogator signal processing system for reading moving transponders
First Claim
1. A method for recovering a backscattered data signal from a radio frequency (RF) transponder comprising the steps of:
- receiving in-phase (I) and quadrature-phase (Q) signals from said RF transponder, said I and Q signals containing said backscattered data signal directly modulated onto an RF carrier wherein a phase angle P(t) between the I and Q signals and said RF carrier is substantially unknown;
estimating said phase angle β
(t) between the I and Q signals and said RF carrier; and
recovering said backscattered data signal by combining said I and Q signals with said estimated phase angle β
(t).
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Accused Products
Abstract
An RF/ID interrogator recovers a backscattered data signal from a moving RF/ID transponder by combining the received in-phase (I) and quadrature-phase (Q) components of the signal in a manner that cancels out the amplitude nulls and phase reversals caused by movement of the RF/ID transponder. More particularly, the RF/ID interrogator comprises a radio having a transmitter portion to provide an RF carrier signal and a receiver portion to receive the I and Q signals from the RF transponder. A bandpass filter is coupled to the radio to remove direct current (DC) components from the I and Q. A processor coupled to the radio and the filter executes stored instructions to combine the filtered I and Q signals and recover the original backscattered data signal therefrom. In an embodiment of the invention, the processor estimates a phase angle β(t) between the I and Q signals and the RF carrier by calculating an arctangent of a ratio of the filtered Q and I signals. Thereafter, the processor recovers the backscattered data signal by summing a product of the filtered I signal and the cosine of the estimated phase angle β(t) with a product of the filtered Q signal and the sine of the estimated phase angle β(t).
144 Citations
25 Claims
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1. A method for recovering a backscattered data signal from a radio frequency (RF) transponder comprising the steps of:
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receiving in-phase (I) and quadrature-phase (Q) signals from said RF transponder, said I and Q signals containing said backscattered data signal directly modulated onto an RF carrier wherein a phase angle P(t) between the I and Q signals and said RF carrier is substantially unknown; estimating said phase angle β
(t) between the I and Q signals and said RF carrier; andrecovering said backscattered data signal by combining said I and Q signals with said estimated phase angle β
(t). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. An apparatus for recovering a backscattered data signal from a radio frequency (RF) transponder, comprising:
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a radio having a transmitter portion to provide an RF carrier signal and a receiver portion to receive in-phase (I) and quadrature-phase (Q) signals from said RF transponder, said I and Q signals containing said backscattered data signal directly modulated onto an RF carrier wherein a phase angle β
(t) between the I and Q signals and said RF carrier is substantially unknown;a bandpass filter coupled to said radio to remove direct current (DC) components from said I and Q signals; a processor coupled to said radio and said bandpass filter, said processor further having a memory containing stored instructions to be executed by said processor, said stored instructions comprising; estimating said phase angle β
(t) between the I and Q signals and said RF carrier; andrecovering said backscattered data signal by combining said filtered I and Q signals with said estimated phase angle β
(t). - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25)
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Specification