System and method for suppressing carrier leakage

Abstract

The invention discloses a system for suppressing carrier leakage, and the system comprises a directional coupler, a quadrature demodulator and a reflection signal module, wherein the directional coupler is used for outputting leaked radio frequency carrier signals from an isolation port to the quadrature demodulator; the quadrature demodulator is used for demodulating out in-phase and quadrature signals from the leaked radio frequency carrier signals, sending the in-phase and quadrature signals to the reflection signal module and utilizing reflection signals reflected from the reflection signal module to suppress the leaked radio frequency carrier signals; and the reflection signal module is used for performing filtration, phase rotation gain control and in-phase and out-of-phase integration on the in-phase and quadrature signals to obtain control signals of the reflection signals, utilizing the control signals to control the reflection signals and sending the reflection signals to the quadrature demodulator. The invention further discloses a method for suppressing the carrier leakage; by adopting the system and the method, leakage of forward radio frequency carrier signals can be simply and effectively suppressed.

Description

technical field [0001] The invention relates to the field of carrier control in an ultra-high frequency passive radio frequency identification system, in particular to a system and method for suppressing carrier leakage. Background technique [0002] In the UHF passive RFID system, when the tag communicates with the reader, the reader needs to always send carrier waves to provide power for the tag, and the tag sends information to the reader by modulating backscatter. Therefore, when the reader receives the signal of the tag, the RF carrier sent forward by the reader will leak to the reverse receiving part of the reader. The strength of the backscattered signal from the tag is very small compared with the strength of the carrier signal sent forward. In the actual system, the strength difference between the reverse signal and the forward signal will reach more than 90dB. Therefore, UHF readers usually use directional couplers to isolate forward and reverse signals. [0003]...

AI Technical Summary

Problems solved by technology

[0004] In the reader, because the antenna impedance is affected by the environment and production process, it is impossible to completely match, the cable length between the antenna and the reader changes, and the device parameters inside the reader will change due to environmental temperature changes and different production batches. , the directional coupler can only provide about 20 to 30dB of isolation under the combined influence, and the isolation effect is not ideal

[0005] Further, some readers use the method of directional coupler and signal combination to generate a signal that cancels the original leakage signal, but the signal combination is performed through the combiner, the structure is complicated, the cancellation efficiency is low, and the combiner will Increase reverse signal insertion loss

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