This paper proposes a tag antenna for radio frequency identification (RFID) food system. The RFID tag antenna is designed and fabricated based on the rectangular loop concept used in the UHF band (Korean and Japanese standards, 916.7 923.5 MHz). The proposed tag antenna is composed of a radiation patch, sensor tag chip, temperature sensor, oscillator, and battery. We conjugated matching between the tag antenna and the sensor tag using a U-shaped stub. Details of the proposed tag antenna design and the simulated and measured results are presented and discussed.Key Words: Food Systems, Semi-Active Sensor, UHF RFID. . INTRODUCTIONRadio frequency identification (RFID) now finds applications in many areas, including logistics tracing, traffic control, environmental surveillance, and medical and grocery tracking. The RFID system consists of a reader and a tag, and the UHF RFID system operates at the bands of North America (902 928 MHz), Europe (865 867 MHz), Japan (916.7 923.5 MHz), and Korea (917 923.5 MHz). RFID is classified into passive and active types according to the method used to obtain the energy source of the electric wave. The passive type obtains the transmission energy from the electric wave received from the reader. The active type obtains the transmission energy from the battery. The passive tag has a semi-permanent life, no battery, is inexpensive, and is suitable for short range communication. On the other hand, the active tag can be used for long range communication because the battery is built into the tag.However, the high price and the battery lifetime currently restrict the use of RFID. Several papers have been published on RFID antennas for both passive and active tags [1][2][3][4][5][6][7][8][9][10][11][12][13], such as a shorted micro-strip patch antenna that uses an inductively coupled feed for the UHF RFID tag [2], miniaturization of a rectangular loop antenna using a meander line for RFID tags [3], RFID tag antennas that use an inductively coupling feed [4], a flexible planar RFID tag antenna with low performance degradation from nearby target objects [8], a broadband UHF RFID tag antenna with a rectangular-loop feed and additional patches [9], a planar loop tag antenna with bandwidth enhancement for the UHF RF-ID system [10], a long range UHF RFID tag with a rectangular metallic cavity structure [11], and a design for an integrated loop coupler and loop antenna for RFID applications [12]. The active RFID can provide long range data transmission because it uses different fields (the environmental monitoring, military, and health care). The requi-

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Accidental falls frequently occur during activities of daily living. Although many studies have proposed various accident detection methods, no highperformance accident detection system is available. In this study, we propose a method for integrating data and accident detection algorithms presented in existing studies, collect new data (from two stunt performers and 15 people over age 60) using a developed wearable device, demonstrate new features and related accident detection algorithms, and analyze the performance of the proposed method against existing methods. Comparative analysis results show that the newly defined features extracted reflect more important risk factors than those used in existing studies. Further, although the traditional algorithms applied to integrated data achieved an accuracy (AC) of 79.5% and a false positive rate (FPR) of 19.4%, the proposed accident detection algorithms achieved 97.8% AC and 2.9% FPR. The high AC and low FPR for accidental falls indicate that the proposed method exhibits a considerable advancement toward developing a commercial accident detection system.