Long Range Passive RF-ID Tag With UWB Transmitter

Transcription

1 Long Range Passive RF-ID Tag With UWB Transmitter Seunghyun Lee Seunghyun Oh Yonghyun Shim

2 About RF-ID Tag What is a RF-ID Tag? An object for the identification using radio waves Reader (Interrogator) / Tag (Transponder) Applications : Tracking, Inventory Systems, etc. Potential Uses: Replacing Barcodes, Low Cost Remote Sensors Advantages: Readable beyond line of sight Information storage of each product Requirements Lower Cost / Smaller Size / Longer Reading Distance

3 Types of RF-ID Tag Active vs. Passive Active RF-ID Tag Passive RF-ID Tag Advantage Longer Reading Distance Semi-permanent Uses / Less Cost Disadvantage Limited Life Cycle Shorter Reading Distance Transmission Method Backscattering UWB Advantage Disadvantage Low Power Consumption Limited Maximum Reading Distance Max Power: 25 % of Incoming Power) Immunity in Multipath Problem Location of RF-ID Recognizable Longer Reading Distance (~ 20 m) Requires more Power Requires Additional Antenna

4 Block Diagram of the Entire System

5 Wireless Power Harvesting Power from Interrogator λrf 2 Receive Power: Pr = PEIRPGr( ) 4π d Use of 4 W EIRP, 915 MHz RF Signal Load Voltage Amplitude: V RL Load = 2 2 R P s r R L + R R S : Antenna Radiation Resistance Input Voltage in Antenna R L : Input Resistance of RF-ID s

6 Voltage Multiplier Dickson Multiplier Rectifying and Boosting RF to DC Bias Output Voltage: Nv For N Stages 2 in Full Wave Multiplier Using Both of Cycles: Shorter Charging Time Output Voltage: Nv For N Stages 4 in Issues in Real Components Voltage Drop in Diodes: Input Voltage Vth Reverse Leakage in Diodes: Minimum size is better. Loss from Parasitic Capacitors and Resistors

7 Multiplier with Resonant Tank LC Resonant Tank Adequate for 50 Ω Antenna Q of Tank: 4 ~ 5 Q of Inductor: 17 ~ 18 Issues Power Loss in LC Resonant Tank Keeping Resonant Condition VR Capacitor: Parasitic Capacitance Simulation Result Vout is less than target voltage. More boosting is difficult. Distance Vin Vout 12 m mv mv 14 m mv mv 16 m mv mv 18 m mv mv 20 m mv mv

8 Use of 300 Ω Radiation Resistance Use Another Antenna Higher Radiation Resistance Resonant Tank: Total Q 1 Issues Design of Matching Network Radiation Resistance: 300 Ω Simulation Result Achieving Target Voltage with 20 m distance (3 db Margin in 10 m distance) 8 stages of Full Wave Multiplier Used Distance Vin Vout 12 m mv V 14 m mv V 16 m mv V 18 m mv V 20 m mv V

9 Capacitors in the Final Stage Required Capacitance 0.1 V Drops (610 µw for 256 ns) 1.6 nf Capacitors Required Simulation Result Time Constant 0.85 ms Expected Charging Time 4.25 ms

10 Voltage Limiter Need for Limiter Large Voltage in Near Distance Protect FETs from high input voltage V out 2 Iin I = 2VD + KW/ L N+ 1 N IoutR0 I in R 0 N + 1 N + 1 n out Simulation Result About 4 V in 1 m distance More Stages Required for Further Protection

11 Schematic and Lock-in Mechanism Vdd = 1.2V, V s = 850mV, V bias = 550 mv Injected Signal : 128mV (20m distance), 915 MHz Oscillator Center Frequency = 917 MHz Target Lock-in Frequency = 915 MHz Total Power Consumption = 97 µa (116.4 µw) LC tank Q = 12.8 g m R p = 3.56

12 Clock Extraction Natural Oscillation Oscillation V p-p : 660 mv Transit delay : 28 ns Frequency : MHz Injection Locked State Oscillation V p-p : 780 mv Transit delay : 26 ns Frequency : MHz

13 Lock-in Range With wider locking range, the lock-in mechanism will be more robust against process and temperature variations. Lock-in range vs Distance 100mV (26 m) 140mV (18m) 200mV (13m) 400mV (6m)

14 Process & Temperature Variation Process Variation Before Lock-in (ω 0 ) Temperature Variation After Lock-in (ω lock = 915MHz) Before Lock-in (ω 0 ) After Lock-in (ω lock = 915MHz)

15 Periodic Steady State Analysis Phase Noise Supply Voltage Variation -86dBc/Hz at 100KHz (-110dBc/Hz at 1MHz) Plot of ω 0 change due to V dd variations Lock-in mechanism will still work from 0.9V to 1.3V (18m distance assumed.)

16 Oscillator Performance Comparison Injection Locking Oscillator Comparison Incident Signal Power Consumption Locking Range Phase Noise This Work 140mV μw (97 μa) 37MHz -86dBc/Hz at 100KHz* (-110dBc/Hz at 1MHz)* Kocer, Flynn (2004) 150mV 450 μa 20MHz -94dBc/Hz at 100KHz Rategh, Lee (1999) 400mV 780 μw (520 μa) 290MHz -100dBc/Hz at 100KHz Tiebout (2004) 1.25 V 23 mw 3GHz (-113dBc/Hz at 1MHz)

17 UWB FCC Emission Limit

18 UWB pulse generation (1) Logical method Very weak to Process Variation Clock Multiplication Our choice Clock with 50% duty cycle has odd harmonic Bandpassfilter

19 UWB pulse generation (2) Differential to Single-ended

20 UWB pulse generation (3) Clock from LC oscillator Bandpass Filter tuned to 5 th Harmonic Amplify the result signal

21 Simulation Result (1)

22 Simulation Result (2) Frequency Range Process Variation Power Consumption Total: 450uW (300 uw in Amp)

23 Layout of the Entire System Inductor LC Oscillator Pulse Generator Voltage Multiplier Capacitor

24 Performance Comparison Total Performance Comparison Maximum Reading Distance RF Input Frequency Transmission Fabrication Technology This Work 10 ~ 20 m 915 MHz UWB 0.13 µm Standard CMOS U.Karthaus (2003) 9.25 m 915 MHz PSK, Backscattering Silicon-on-Sapphire J. Curty (2005) 12 m 2.45 GHz ASK, Backscattering CMOS with Schottky Diode M. Baghaei (2007) 10.7 m 915 MHz UWB LCP with 0.18 µm CMOS

25 Future Work 1. Startup Circuit Enable Signal After Charging completed Minimum Loading Effect 2. Control Logic / ROM Minimum Power Consumption 3. Optional Regulator Receiver