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 Net-

works” – 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 Volt-age(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

VDC

P_1TonePORT1

Freq=RFfreqP=dbmtow(RFpower)Z=50Num=1

DC_BlockDC_Block1

dongbu13rfvp5_nmos_rfnmos_rf8

nr=fingerwu=wu_vallr=ir_valModel=nmos_rf

dongbu13rfvp5_nmos_rfnmos_rf9

nr=fingerwu=wu_vallr=ir_valModel=nmos_rf

DC_FeedDC_Feed1

I_ProbeI_Probe1 V_DC

SRC5Vdc=VDS

DC_BlockDC_Block2

TermTerm2

Z=50Num=2

V_DCSRC6Vdc=VGS

DC_FeedDC_Feed2

Amplifier Design

Minimize Power Consumption

Minimum Power Consumption

Impedance matching

1

2 2

1

Impedance matching

Optimal goal Minimum power consumption

Limitation of inductance

Optimal power consumption Reasonable inductor

Multilayer Ceramic Chip Induc-tors

18dB Amplifier

VDC

0 V

350 mV

1.20 V

52.4 uA

-52.4 uA

16.5 pA -19.6 pA

dongbu13rfvp5_nmos_rfnmos_rf8

nr=fingerwu=wu_vallr=ir_valModel=nmos_rf

52.4 uA

-52.4 uA

103 pA -46.9 pA

dongbu13rfvp5_nmos_rfnmos_rf9

nr=fingerwu=wu_vallr=ir_valModel=nmos_rf

0 A

CC2C=87 fF

0 AP_1TonePORT1

Freq=RFfreqP=dbmtow(RFpower)Z=50Num=1

0 ACC4C=10.0 pF

0 A LL2

R=3L=150 nH

-52.4 uAV_DCSRC5Vdc=VDS

-16.5 pA

V_DCSRC6Vdc=VGS

0 A

TermTerm2

Z=50Num=2

52.4 uALL1

R=1.5L=82.5 nH

0 ACC3C=160 fF

0 ACC1C=160 fF

-16.5 pA

LL3

R=L=47 uH

-52.4 uA I_ProbeI_Probe1

Simulation result

freq (800.0MHz to 1.000GHz)

SP_C

ircle

.SP.S

(1,1

)

freq (916.0MHz to 916.0MHz)

SP_916.S

P.S

(1,1

)

Input Reflection Coefficient

freq (800.0MHz to 1.000GHz)

SP_C

ircle

.SP.S

(2,2

)

freq (916.0MHz to 916.0MHz)

SP_916.S

P.S

(2,2

)

Output Reflection Coefficient

0.90.8 1.0

-25

-20

-15

-10

-5

0

5

10

15

-30

20

freq, GHz

dB(S

P_C

ircle

.SP.S

(2,1

))dB(S

P_C

ircle

.SP.S

(1,1

))

Forward Transmisstion, dB

freq

915.0 MHz

SP_915.Zin1

52.556 - j9.743

SP_915.Zin2

51.334 + j7.984

SP_915.MaxGain1

18.990

db(SP_915.SP.S(2,1))

18.922

SP_915.SP.nf(2)

2.183

Simulation result of 70 dB Amplifier

freq

915.0 MHz

SP_915.Zin1

53.086 - j10.417

SP_915.Zin2

53.752 + j6.759

SP_915.MaxGain1

75.704

db(SP_915.SP.S(2,1))

75.632

SP_915.SP.nf(2)

2.202

freq (800.0MHz to 1.000GHz)

SP_C

ircle

.SP.S

(1,1

)

nothing (-1.000 to 1.000)

SP_916.S

P.S

(1,1

) <in

valid

>

Input Reflection Coefficient

freq (800.0MHz to 1.000GHz)

SP_C

ircle

.SP.S

(2,2

)

nothing (-1.000 to 1.000)

SP_916.S

P.S

(2,2

) <in

valid

>

Output Reflection Coefficient

0.90.8 1.0

-20

0

20

40

60

-40

80

freq, GHz

dB(S

P_C

ircle

.SP.S

(2,1

))dB(S

P_C

ircle

.SP.S

(1,1

))

Forward Transmisstion, dB

RF wake-up circuit diagram

Simulation result of RF wake Sensor

915.9 MHz 916.1 MHz

914.1 MHz 917.19MHz

Why isn`t it working cor-rectly?

915 916 917914 918

-30

-25

-20

-15

-10

-5

-35

0

freq, MHzdB

(S(2

,1))

Forward Transmission, dB

LL9

R=1e-12 OhmL=8 pH

CC13C=3.775 nF {-t}

LL10

R=1e-12 OhmL=8 pH

CC14C=3.775 nF

Simulation result of RF wakeup Sensor

Delay analysis

Data packets can be transmitted after 2-hop neighbors send wakeup signals, to avoid collision and interference

Power Analysis