RF Wakeup Sensor – On-Demand Wakeup for Zero Idle Listening and Zero Sleep Delay

Sensor node Sensor node with RF wake-up  RF wakeup sensor  Sense RF signal from antenna with very low power consumption  RF transceiver is turned off and all the other parts of a sensor is in sleep mode  When RF signal is detected, the RF wake-up sensor interrupts to the processor RF Wakeup Sensor

Related Works  MAC layer approach  Sensor nodes sleep and wake up periodically to reduce energy consumption  Trade-off between energy consumption and message latency  Physical layer approach  “Passive Wakeup Scheme for Wireless Sensor Networks” – ICICIC 2007  Add 125kHz wake-up module  Wake-up sensor with a different frequency band requires extra transceiver and antenna for 125kHz frequency  “Highly Sensitive CMOS Passive Wakeup Circuit” – APMC 2008  Too small sensitivity (-30 dBm) – Transmission range of only 3~10 cm  No consideration for data communication and networking  “A Novel Wireless Wake-up Mechanism for Energy-efficient Ubiquitous Networks” – GreenComm 2009  Consider data communication but not for networking  Too small sensitivity (-37 dBm)

RF Wakeup Sensor Design  Goal  Sensitivity as high (-100 dBm with transmission range of 100 meters) as the target RF transceiver  Ultra low power consumption targeting three orders of magnitude reduction (1/1000) compared to the target RF transceiver  Target sensor node (CC1000 – Transceiver)  915 MHz with 100kHz band, FSK modulation, 40kbps, -100 dBm  Power consumption  Sleep : 3uW  RX : 30 mW  TX : 50 mW

RF Wakeup Sensor Design  Amplifier  Similar to LNA (low noise amplifier) design  Limit noise  Need 70 dB gain  Increase the insufficient sensitivity (-100 dBm) of detector to -30 dBm  Input-output matching networks  Also used for channel selection  Detector  Detector with diode rectifier  Detect -30 dBm with no bias  Detect -40 ~ -50 dBm with a small uA bias

Amplifier  Target channel  Amplify the signal with the minimum strength (-100dBm) to -30dBm  Neighbor channel  Limit the signal with the maximum strength (-30dBm) to prevent the false detection

Detector  Rectifier  Convert AC to DC (strictly speaking, pulsating DC)  Voltage sensor ( switch )  Interrupt to the processor when voltage is higher than a threshold Rectifier Simple Voltage(power) Sensor

 Cascode amplifier  Based on LNA design  Minimize Power Consumption  Low current bias  Transistor size, Vgs  Impedance matching  Limitation of inductor  Inductance, Q factor, SRF (Self Resonating Frequency)  Optimum goal  High gain  Low power consumption  Reasonable inductor Amplifier Design

Minimize Power Consumption

Minimum Power Consumption

Impedance matching

Optimal goal  Minimum power consumption  Limitation of inductance  Optimal power consumption  Reasonable inductor

Multilayer Ceramic Chip Inductors

18dB Amplifier

Simulation result

Simulation result of 70 dB Amplifier

RF wake-up circuit diagram

Simulation result of RF wake Sensor MHz MHz MHz MHz

Why isn`t it working correctly?

Simulation result of RF wakeup Sensor

Delay analysis

Power Analysis