An RF-Powered Temperature Sensor Designed for Biomedical Applications Gustavo Campos Martins, Fernando Rangel de Sousa GRF, UFSC September 4, 2013 Gustavo C. Martins (GRF, UFSC) RF-Powered Temperature Sensor September 4, 2013 1 / 26
Summary 1 Introduction 2 System Architecture 3 RF Front End 4 Analog Circuits 5 Full-system Simulations and Measurement Results 6 Conclusion Gustavo C. Martins (GRF, UFSC) RF-Powered Temperature Sensor September 4, 2013 2 / 26
Summary Introduction 1 Introduction 2 System Architecture 3 RF Front End 4 Analog Circuits 5 Full-system Simulations and Measurement Results 6 Conclusion Gustavo C. Martins (GRF, UFSC) RF-Powered Temperature Sensor September 4, 2013 3 / 26
Motivation Introduction Continuous patient monitoring Early detection of complications by continuous sensing of vital signs Small wireless devices: no battery Gustavo C. Martins (GRF, UFSC) RF-Powered Temperature Sensor September 4, 2013 4 / 26
RF-Powered sensors Introduction Reader device: sends energy and receives data Sensor device: receives energy and sends data Energy Sensor Data Reader This work: an RF-powered temperature sensor to measure human body temperature (35 to 42 o C) Gustavo C. Martins (GRF, UFSC) RF-Powered Temperature Sensor September 4, 2013 5 / 26
Summary System Architecture 1 Introduction 2 System Architecture 3 RF Front End 4 Analog Circuits 5 Full-system Simulations and Measurement Results 6 Conclusion Gustavo C. Martins (GRF, UFSC) RF-Powered Temperature Sensor September 4, 2013 6 / 26
System Architecture Impedance Matching RF-DC Regulator Reference Source Limiter Mode Selector Backscattering Input signal frequency: 900 MHz Fabrication technology: IBM 130 nm Gustavo C. Martins (GRF, UFSC) RF-Powered Temperature Sensor September 4, 2013 7 / 26
Summary RF Front End 1 Introduction 2 System Architecture 3 RF Front End 4 Analog Circuits 5 Full-system Simulations and Measurement Results 6 Conclusion Gustavo C. Martins (GRF, UFSC) RF-Powered Temperature Sensor September 4, 2013 8 / 26
RF Front End Backscattering Impedance Matching RF-DC Regulator Reference Source Limiter Mode Selector Backscattering Reader Gustavo C. Martins (GRF, UFSC) RF-Powered Temperature Sensor September 4, 2013 9 / 26
RF Front End Backscattering and Impedance Matching Impedance Matching RF-DC Regulator Reference Source Limiter Mode Selector Backscattering RF-DC... 0-10 S11 (db) -20-30 -40-50 0 0.2 0.4 0.6 0.8 1 1.2 V bks (V) Gustavo C. Martins (GRF, UFSC) RF-Powered Temperature Sensor September 4, 2013 10 / 26
RF Front End Backscattering and Impedance Matching Impedance Matching RF-DC Regulator Reference Source Limiter Mode Selector Backscattering RF-DC... 0 500 10 400 S11 (db) 20 30 Amostras 300 200 40 100 50 800 850 900 950 1000 f (MHz) 0 80 70 60 50 40 30 20 10 S11 (db) Worst case S11 in the Monte Carlo simulation = 15 db Gustavo C. Martins (GRF, UFSC) RF-Powered Temperature Sensor September 4, 2013 11 / 26
RF Front End Rectifier Impedance Matching RF-DC Regulator Reference Source Limiter Mode Selector 16 Stages Backscattering...... Doubler Stage Native transistors in diode configuration Output conditions: V dc = 1 V e I dc = 10 µa Power convertion efficiency: PCE = P dc P av = 10% Gustavo C. Martins (GRF, UFSC) RF-Powered Temperature Sensor September 4, 2013 12 / 26
Summary Analog Circuits 1 Introduction 2 System Architecture 3 RF Front End 4 Analog Circuits 5 Full-system Simulations and Measurement Results 6 Conclusion Gustavo C. Martins (GRF, UFSC) RF-Powered Temperature Sensor September 4, 2013 13 / 26
limiter Analog Circuits Impedance Matching RF-DC Regulator Reference Source Limiter Mode Selector Backscattering I (µa) 1400 1200 1000 800 600 400 200 0 0 0,2 0,4 0,6 0,8 1 1,2 1,4 1,6 V DD (V) 1,5 1,2 V dc (V) 0,9 0,6 0,3 0,0-15 -10-5 0 5 10 15 20 P av (dbm) Gustavo C. Martins (GRF, UFSC) RF-Powered Temperature Sensor September 4, 2013 14 / 26
Mode Selector Analog Circuits Impedance Matching RF-DC Regulator Reference Source Limiter Mode Selector Backscattering 0.25 0.2 V ref V slope Inputs (V) 0.15 0.1 0.05 0 0 0.2 0.4 0.6 0.8 1 1.2 V dc (V) V ctr (V) 1,2 1 0,8 0,6 0,4 0,2 0-0,2 0 0,3 0,6 V off 0,9 V on 1,2 V dc (V) Gustavo C. Martins (GRF, UFSC) RF-Powered Temperature Sensor September 4, 2013 15 / 26
Analog Circuits Regulator Impedance Matching RF-DC Regulator Reference Source Limiter Mode Selector Backscattering Gustavo C. Martins (GRF, UFSC) RF-Powered Temperature Sensor September 4, 2013 16 / 26
Analog Circuits Temperature Sensor Impedance Matching RF-DC Regulator Reference Source Limiter Mode Selector Backscattering Reference generator TC I 1 V t8 V t8 T 1 R 1 R 1 T f I bias = KI ref Gustavo C. Martins (GRF, UFSC) RF-Powered Temperature Sensor September 4, 2013 17 / 26
Temperature Sensor Analog Circuits Impedance Matching RF-DC Regulator Reference Source Limiter Mode Selector Backscattering I ref (na) 640 630 620 610 600 590 580 110 108 106 104 102 100 98 35 36 37 38 39 40 41 42 T ( o C) I ref V ref V ref (mv) I ref (na) TC I = 1.22 %/ o C, I ref = 613 na 800 600 400 120 100 80 60 40 200 I ref 20 V ref 0 0 0.2 0.4 0.6 0.8 1 1.2 0 V dd (V) V ref (mv) Calibration method to achieve less than 0.2 o C measurement error Gustavo C. Martins (GRF, UFSC) RF-Powered Temperature Sensor September 4, 2013 18 / 26
Summary Full-system Simulations and Measurement Results 1 Introduction 2 System Architecture 3 RF Front End 4 Analog Circuits 5 Full-system Simulations and Measurement Results 6 Conclusion Gustavo C. Martins (GRF, UFSC) RF-Powered Temperature Sensor September 4, 2013 19 / 26
Simulation Full-system Simulations and Measurement Results Impedance Matching RF-DC Regulator Reference Source Limiter Mode Selector Backscattering Gustavo C. Martins (GRF, UFSC) RF-Powered Temperature Sensor September 4, 2013 20 / 26
Full-system Simulations and Measurement Results Simulation V dd (V) V dc (V) V bks (V) 1,2 1 0,8 0,6 0,4 0,2 0 0 10 20 30 40 50 60 70 t (µs) 1,2 1 0,8 0,6 0,4 0,2 0 0 10 20 30 40 50 60 70 t (µs) 1,2 1 0,8 0,6 0,4 0,2 0 0 10 20 30 40 50 60 70 t (µs) Gustavo C. Martins (GRF, UFSC) RF-Powered Temperature Sensor September 4, 2013 21 / 26
Full-system Simulations and Measurement Results Measurement Results - Rectifier -5-10 S11 (db) -15-20 -25-30 -35-40 Medido Simulado -45-50 800 850 900 f (MHz) 950 1000 PCE = 10% for Pav = 10 dbm, Vdc = 1 V and Idc = 10 µa Gustavo C. Martins (GRF, UFSC) RF-Powered Temperature Sensor September 4, 2013 22 / 26
Full-system Simulations and Measurement Results Measurement Results - Limiter and Backscattering I (µa) 10 4 10 3 10 2 10 1 10 0 10-1 10-2 Simulation Measurements Limiter 10-3 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 V DD (V) S11 (db) 0-5 -10-15 -20-25 -30-35 -40-45 Backscattering Measurements Simulation 0 0,2 0,4 0,6 0,8 1 1,2 V bks (V) Gustavo C. Martins (GRF, UFSC) RF-Powered Temperature Sensor September 4, 2013 23 / 26
Summary Conclusion 1 Introduction 2 System Architecture 3 RF Front End 4 Analog Circuits 5 Full-system Simulations and Measurement Results 6 Conclusion Gustavo C. Martins (GRF, UFSC) RF-Powered Temperature Sensor September 4, 2013 24 / 26
Comparison Conclusion An RF-powered temperature sensor (35 to 42 o C) that has measurement error < 0.2 o C was designed and partially tested Reference [1] [2] [3] [4] [5] This work Technology ( nm) 250 130 130 130 180 130 Frequency ( MHz) 450 900 900 868 910 900 Area ( mm 2 ) 1.2-0.95 3.96 1.2 0.34 Standby power ( µw) 5 6-0.11-4.9 Active power ( µw) 1500 9 7.9-7 8.5 PCE (%) - 30 7.6 35-10 P av,min (dbm) 12.5 12 10.3-5 10 [1] KOCER, F.; FLYNN, M. An rf-powered, wireless cmos temperature sensor. Sensors Journal, IEEE, 2006. [2] YEAGER, D. et al. A 9 µa, Addressable Gen2 Sensor Tag for Bio-signal Acquisition. Solid-State Circuits, IEEE Journal of, 2010. [3] REINISCH, H. et al. A multifrequency passive sensing tag with on-chip temperature sensor and off-chip sensor interface using epc hf and uhf rfid technology. Solid-State Circuits, IEEE Journal of, 2011. [4] VAZ, A. et al. Full passive uhf tag with a temperature sensor suitable for human body temperature monitoring. Circuits and Systems II: Express Briefs, IEEE Transactions on, 2010. [5] QIAN, J. et al. A passive UHF tag for RFID-based train axle temperature measurement system. In: Custom Integrated Circuits Conference (CICC), 2011 IEEE, 2011. Gustavo C. Martins (GRF, UFSC) RF-Powered Temperature Sensor September 4, 2013 25 / 26
Conclusion Thank you! http://rfic.ufsc.br/ gustavocm@ieee.com Gustavo C. Martins (GRF, UFSC) RF-Powered Temperature Sensor September 4, 2013 26 / 26