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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