• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.2
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• pp.152-159
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• 2019

In general, a Doppler radar can measure only the velocity of a moving target. To measure the distance of a moving target, it is necessary to use a frequency-modulated continuous wave or pulse radar. However, the latter are very complex in terms of both hardware as well as signal processing. Moreover, the requirement of wide bandwidth necessitates the use of millimeter-wave frequency bands of 24 GHz and 77 GHz. Recently, a new kind of Doppler radar using multitone frequency has been studied to sense the distance of moving targets in addition to their speed. In this study, we show that distance sensing of moving targets is possible by adjusting only the frequency of a 2.4 GHz Doppler radar with low cost phase lock loop. In particular, we show that distance can be sensed using only alternating current information without direct current offset information. The proposed technology satisfies the Korean local standard for low power radio equipment for moving target identification in the 2.4 GHz frequency band, and enables multiple long-range sensing and radio-frequency identification applications.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.5
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• pp.348-355
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• 2019

UHF and microwave RFID systems are widely applied in various fields because they can read a plurality of tag information within a radius of several meters ahead of the RFID reader. However, they cannot detect the position of the tag in applications that recognize only a tag at a specific position. In this study, we propose a new RFID system that can interrogate the tag of a specific location selectively by using the position information of the tag. This can be done by only adjusting the reader's operating frequency. To verify the feasibility of the proposed system, we implemented a 2.4 GHz RFID reader whose frequency can be varied by using a phase-locked loop circuit and a backscattered tag. Experimental results confirm that the tag position can be sensed exactly.