수동형 태그 기반 RFID 리더기의 수신부 모듈 감도 개선

Abstract

The Radio Frequency Identification(RFID) system is a sort of Automatic Identification. Using a reader, transponder and antenna etc, it identifies the information of transponder by means of a contactless reading and radio frequency. In this paper, we propose a new RFID Module based on Passive tag(operating in range of 908.5 ～ 914MHz) to break through the problems of the existing system, which uses a circulator to keep a direction of power flowing in the reader's receiver regularly. Also it adopts a Low Noise Amplifier(LNA) in front of receiver to eliminate non-wanted noise power mixed with signal power. Using the Surface Acoustic Wave(SAW) filter, instead of LC resonance filter, it is possible that it can improve the sensitivity of receiver largely filtering a wanted frequency and reducing many noisy sources generated generally by white noises. We have simulated with Advanced Designed System-2004A to compare whether to improve the sensitivity of the operation frequency and the reader's tag properties and analysis or not, performing of the reader module between the advanced system and the existing systems. The commercial receive system causes a loss of sensitivity because of using 24 capacitors and 6 inductors. So by using a circulator(it minimizes the interference), Voltage Control Oscillator, Low Noise Amplifier, Surface Acoustic Wave filter(it eliminates the power of noises in the transceiver), we have designed an improved receive system in terms of reducing sensitivity largely. The advanced system has properties of that; 1. Use a circulator to reduce the interface and a non-wanted cross-modulation The circulator locates in front of receiver and separates the path of Tx/Rx signals to eliminate interference. Also removing the backward power signals and blocking off a cross-modulation, it improves the receiver's performance in sensitivity largely. 2. Adopt a Low Noise Amplifier to minimize the Noises in received signals and to maximize the signal's gain of amplifying. 3. Use a SAW filter instead of LC resonance filter to make it smaller as possible as. the LC filter has a group delay and a loss of insert occupying a large volume. However, a narrow bandwidth of SAW filter makes it the frequency selectivity better to improve the group delay and the lose of insert specifics. What is better, it also enables a dimension of filter to be smaller and manufacture the receive system to be more smaller.