Pulse or digital communications – Receivers – Angle modulation
Patent
1998-09-15
2000-09-19
Pham, Chi H.
Pulse or digital communications
Receivers
Angle modulation
375130, 342 42, H04B 1500, H03D 322, G01S 1374
Patent
active
061223298
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 .beta.(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 .beta.(t) with a product of the filtered Q signal and the sine of the estimated phase angle .beta.(t).
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Chieu Trieu C.
Zai Li-Cheng
Intermec IP Corp.
Pham Chi H.
Tran Khai
LandOfFree
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