Design of a Wireless Self-Powered Temperature Sensor for UHF Sensor Tags

무선 전력 구동 센서 태그 내장형 온도센서의 설계

  • Kim, Hyun-Sik (Department of Electrical Engineering, Chungbuk National University) ;
  • Cho, Jung-Hyun (Department of Electrical Engineering, Chungbuk National University) ;
  • Kim, Shi-Ho (Department of Electrical Engineering, Chungbuk National University)
  • Published : 2007.10.25

Abstract

Wireless Self-Powered Temperature Sensor for UHF Sensor Tags which are basic device for construction of ubiquitous sensor network is proposed. The key parameters of the target specification are resolution of $0.1\;^{\circ}C$ per output bit, below 1.5 V of operating voltage and below 5 uW of power consumption during sensing operation. Temperature sensor circuit consists of PTAT current generator, band gap reference circuit generating both reference voltage and current, Sigma-Delta Converter, and Digital Counter. Simulated maximum resolution was $0.23\;^{\circ}C/bit$ in 11-bit output. The proposed temperature sensor was fabricated by using a 0.25 m CMOS process. The chip area is $0.32\;{\times}\;0.22\;mm$ and the operating frequency is 2 MHz. Measured resolution from fabricated temperature sensor was $4\;^{\circ}C/bit$ in 8-bit output for the temperature range from $10^{\circ}C$ to $80^{\circ}C$.

UHF RFID 태그에 내장하여, 유비쿼터스 센서 네트워크의 구성 기초 소자로 활용 가능한 온도센서 회로를 제안하였다. UHF RFID 내장을 위해 1.5 V 이하의 저전압, 5 uW의 동작 소비 전력소비, $0.1\;^{\circ}C/bit$의 해상도를 설계 목표로 하였다. 온도센서의 구성은 PTAT 전류 발생기, 기준 전류와 전압 발생 회로, 시그마 델타 변환기, 디지털 카운터로 구성되어 있다. 제안된 온도센서는 $0.1\;^{\circ}C/bit$의 해상도를 목표로 설계하였지만, 시뮬레이션에서는 11-bit 출력에서 최대 $0.23\;^{\circ}C/bit$의 해상도를 얻을 수 있었다. 0.25 um CMOS 공정을 설계 및 제작하였고, 전원 전압은 1.5 V, 칩의 면적은 $0.32\;{\times}\;0.22\;mm$이고 동작주파수는 2 MHz이다. 제작된 온도센서의 해상도를 측정한 결과 8-bit 출력에서 평균 $4\;^{\circ}C/bit$로 측정되었다.

Keywords

References

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