Carrier cancelling circuit system for removing carrier jamming of receiving loop

Abstract

The invention relates to a carrier cancelling circuit system for removing carrier jamming of a receiving loop. The carrier cancelling circuit system is located at an RFID (radio frequency identification devices) reader-writer end and comprises a circulator, wherein a signal input end TX-S of the circulator is connected with an output end of a PA (power amplifier) module; a carrier signal TX-S is subjected to power amplification by the PA module and transmitted to an antenna via the circulator; a label return signal RX-S returns to an RX-S signal end of the circulator; and the system further comprises a carrier cancelling LNA (low-noise amplifier) differential amplification circuit, a preposed amplitude and phase adjustment circuit, and a digital control circuit for controlling and adjusting the amplitude and phase adjustment circuit. The system can achieve reject and remove the leaked carrier signal via a high common mode rejection ratio of the carrier cancelling LNA differential amplification circuit, is simple in circuit structure, low in cost and easy to realize, can allow a narrow-band transceiver circuit to have very high isolation and completely meets requirements of a reader-writer on high receiving sensitivity and long-range identification.

Description

technical field [0001] The invention relates to the field of carrier elimination, in particular to a carrier elimination circuit system for eliminating carrier interference of a receiving loop in an ultra-high frequency radio frequency identification reader. Background technique [0002] With the introduction of the concept of the Internet of Things, radio frequency identification technology has developed rapidly and has been widely used in industry, agriculture, commerce and other fields, such as bus toll collection systems, logistics management, personnel safety monitoring, production process control, and commodity management in supermarkets, etc. , RFID technology has penetrated into every aspect of people's lives. [0003] The radio frequency identification system is mainly composed of a reader, a transponder (tag) and a background data processing system. The sensitivity of the reader, the sensitivity of the transponder (tag) and the backscattering performance determine ...

AI Technical Summary

Problems solved by technology

In their patent Balanced circulator structure with enhanced isolation characteristics, W.Lim and J.Yu proposed a method of using two antennas to separate the transmitting and receiving signals. Although this method can improve the isolation, it also increases the system Complexity and cost; Pekka Pursula and others proposed a carrier cancellation circuit with quadrature feedback in the patent Mikko Kiviranta and Heikki Seppa. UHF RFID Reader with Reflected Power Canceller, which can increase the dynamic range of the receiver by about 10dB; by Zhang Jun , Yan Xiucheng proposed a directional coupler carrier cancellation circuit using PIN diodes to form a reflection modulator in a UHF RFID self-interference carrier cancellation device, and the carrier wave at the receiving end was suppressed by 42dB

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