A kind of carrier cancellation method and cancellation circuit of UHF RFID reader

Abstract

The invention discloses a counteracting method and counteracting circuit for carrier wave of an ultrahigh-frequency radio frequency identification device (RFID) reader-writer. The counteracting method comprises the following steps: enabling a counteracting signal to keep at a fixed amplitude to perform angle transverse step by step in a 360-degree range; acquiring an optimal phase angle when signal amplitude formed by adding the counteracting signal and an interference signal is minimum; performing amplitude transverse at the optimal phase angle according to a setting amplitude stepping value; acquiring an optimal counteracting point when the signal amplitude formed by adding the counteracting signal and an interference signal is minimum; performing transverse around the optimal counteracting point by the setting stepping value according to the set range; and acquiring the optimal counteracting point for counteracting when the signal amplitude formed by adding the counteracting signal and an interference signal is minimum. A counteracting circuit is formed by general radio frequency circuit elements, and is low in cost relative to a chip of an integrated reader / writer. By adopting the counteracting method, the counteracting time can be saved, and the reading velocity is improved.

Description

[technical field] [0001] The invention relates to a UHF RFID reader-writer, in particular to a carrier cancellation method and a cancellation circuit for a UHF RFID reader-writer. [Background technique] [0002] During the working process of the UHF RFID reader, when the electronic tag returns a signal to the reader, the reader also needs to transmit a carrier signal to provide energy to the electronic tag. Since the transmitted carrier signal is much larger than the tag return signal, such as figure 1 In the traditional UHF radio frequency identification reader circuit shown, an isolation device is generally added between the transmitting and receiving circuits. Isolation devices usually choose circulators or directional couplers. After the transmitted signal passes through the isolator, part of the signal still leaks to the receiving circuit, and the signal reflected by the antenna also enters the receiving circuit. If these two parts of the signal are too large, the rec...

AI Technical Summary

Problems solved by technology

Every time a point is scanned, it needs to wait for a series of circuit stabilization processes such as DAC output stabilization, amplitude and phase adjustment circuit stabilization, adder stabilization, and ADC stabilization, which takes a lot of time and affects the card reading speed.

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