Distribution Statement A – Approved for Public Release, Distribution Unlimited

www.darpa.mil

: Near Zero Power RF and Sensor Operations (N-ZERO)

Asleep Yet Aware, Awake on DeclareVirginia Efficient Near-zero Ultra-low-power SystemSteven M. Bowers1, Benton Calhoun1, N. Scott Barker1, and Songbin Gong2 1University of Virginia, 2University of Illinois

Activity Factor (N) [#Events/Hr]

Sens

or N

ode L

ifetim

e [Ye

ars]

Ambient Signatures

PowerUnit

TransceiverInfraredRadiation

AcousticChemicalMagnetic

Vibration

Wakeup Receiver

RF Wakeup

Sensing UnitsMemory

Embedded µP + DSP+ FPGA

TRx

Comparator = 2.6nW

Baseband Amp = 2nW

Offset Controller = 1nWCorrelator = 0.8nW

Level Shifters = 0.7nWOscillator = 0.3nW

Total = 7.4nW

DC Power Consumption

0 2 4 6 8 10 12010

0.6

0.10.15

0.2

03060

Sign

al Vo

ltage

(V)

Offset Code

Time (S)

Wakeup Signal

Comparator OutBaseband Amplifier Output

Comparator Offset

Offset Control Reset

-75dBm Wakeup(Success)

-68dBm Interferer Starts (3MHz from Sig)

-75dBm Wakeup (Below Threshold)

-72dBm Wakeup (Success)

Fully-Integrated Automatic Offset Control Demonstration

Envelope Detector BB Amp Comparator Digital Logic

3250 µm

600 µ

m

Overview of Event Driven Sensor Nodes

Event Duration

Waiting Time

No wakeup

Sleep

RF/ambient wakeup

Active

Stay on for ton

WuRxSelf-DischargeTransmitter

WuRxSelf-DischargeTransmitter

!"#$ =&"#$

'()*+)* + 1 − '()* +/0112 + +01#3#41

195 mAh

10 sec 1 mA Self-Discharge

WuRx and other Sleep Power

For event driven sensor nodes with low activity factors, WuRxpower can dominate battery lifetime.

The self discharge of a battery is about 10nW. Assuming that a sensor node turns onfor approximately 10 seconds to take a measurement and transmit the data back,and uses 1mA DC current draw during active mode, it becomes critical to keep all asleep mode power including the WuRx below 100nA and even 10nA for activityfactors less than once per hour [2].Similarly, receiver sensitivity is of fundamental performance as it enables sensors tobe activated at larger distances.Through the N-Zero program, critical metrics such of power consumption andreceiver sensitivity are improved by greater than 1 and 2 orders of magnituderespectively.

üProb. Of Detect.: >99% ü False Alarm Rate: <1/hour üSignal Detection: <2mS

Envelope detector first architectureutilizes passive voltage gain followed by anenvelope detector. Low frequencybaseband amplification can achieve noiselimited, not voltage limited operation, andultra low power digital correlation rejectsfalse positives while maintainingsensitivity. Automatic offset calibrationmaintains functionality in the presence ofprocess and temperature variation andexternal interferes. [1]

RF Wakeup

Virginia Efficient Near-zero Ultra-low-power System (VENUS) Concept

How Low is Low Enough Power? Acoustic MEMS Devices Interference and Process Variation Rejection

Sens

itivi

ty [d

Bm]

Power Consumption [nW]

[ISSCC’15][VLSI’14]

[ISSCC’10][ISSCC’10]

[ISSCC’08][ISSCC’11][ISSCC’17] [RFIC’17]

[ISSCC’16]

This Work

DARPA NZero

System Opportunities:Large Scale Fields of Sensor Nodes that can last for years on a small coin-cell batteryOngoing Needs:Sensitivity, High RF Freq., Self-Calibration, Node Selectivity, Efficient Low Power Transmitter

DARPA N-ZERO

Lithium Niobate Chip CompressorsAcoustic RF Filters and Impedance Transformers

Passive Envelope Detector

SH0 Mode

TB = 60FBW = 50%

S0 Mode

TB = 151FBW = 50%Lin/Lout=14.1

START

RESET

SAMPLE INCOMING

SIGNAL

COUNT_Z++

SAMPLE INCOMING

SIGNALCOMP_OUT == 1

?

COMP_OUT == 1?

WAIT THR_O CLOCK CYCLES

COMP_THR++

RESET Z_CTR

COUNT_Z == THR_Z

?Y

N

Y

N N

Y

COMP_THR - -RESET Z_CTR

Frequency (MHz)100 1000433151.8O

utp

ut

Vo

lta

ge

(m

V/n

W)

6.415.2

11

00

10

0.1

Detector OCVS Versus frequency

16 VIN

CLK

CLK CLK_VX

+ -A0VRF-VOffset

Course offset controlFine offset control

Input preamp

Regen. amp

Kickback reduction

Latch for regeneration D QVX

VDDLComparator

Output

D Q

CLK

Φ

Φ

DFF

DFF

Input Cascode

Sized for 1/f noise

Sets lower cut off

Power supply filter AC

couplingSets upper

cut off

Output Stage

Ultra-Low Power Active Circuits System Performance

Optimum Decision Voltage

Interferer induced offset

Thermal Drift

p(V|X)

V0V VRF

Interferer induced offset

-80 -78 -76 -74 -72 -70

10-3

10-2

10-1

100Wakeup Receiver Sensitivity

Pro

bab

ility

of M

isse

d

Det

ecti

on

Input RF Power (dBm)

433 MHz151.8 MHz

False Wakeup Rate <1/Hr

10-3 Sensitivity

ü DC Power: <10 nWü Sensitivity: -76 dBmü Signal Energy: <30pJ

CMOS Chip

MEMS Device

INPUT

MEMS Chip

INPUT

Buffer(Not Used)

CMOS Chip

OUTPUTRs=66k

References

Transformer 2-Port AlN

2-Port AlN

2-Port LN

1-port AlN + lumped

Frequency (MHz)

358 506 260 447

Open Circuit Voltage Gain

16.0 7.3 35 27

Opportunities: Very high quality factors enable transformations to very large impedances found withinultra low power systems.

Opportunities: Create very sensitive,passive detection by trading offsensitivity, speed and inputimpedance at frequencies where lowpower RF amplification is notattainable. RF frequencies detectableat a GHz or more [2].

Opportunities: Enables detection ofmV level baseband signals whileconsuming just a few nW of power.Increase reliability and error correctfor imperfect RF and mixed signalcircuits and provide selectivitybetween signals [1,3].

Baseband Amplifier:

Comparator

System Design

Opportunities: Enable robust performance in a variety of electromagnetic environments byactuating the receiver threshold based upon measured response of the comparator.

[1] J. Moody et al., "A -76dBm 7.4nW Wakeup Radio with Automatic Offset Compensation," ISSCC, Feb. 2018. [2] P. Bassirian, et al., “Analysis of Quadratic Dickson Based Envelope Detectors for IoE Sensor Node Applications,” IEEE IMS, pp. 215-218, June 2017.[3] H. Jiang et al., "A 4.5nW Wake-Up Radio with −69dBm Sensitivity," ISSCC, pp. 416-417, Feb. 2017.[4] T. Manzaneque, et al., “Lithium Niobate Chirp Compressors for RF front ends of IoT Devices,” in JMEMS, vol. 26, no. 6, pp. 1204-1215, Dec. 2017.[5] T. Manzaneque, et al., , “An SH0 Lithium Niobate Trans-impedance Chirp Compressor with High Voltage Gain”, in 2018 IEEE MEMS, pp. 783-786

Lithium Niobate - CMOS Integration

Source: DARPA

The material is based upon work supported by the Defense Advanced Research Projects Agency (DARPA). The views, opinions and/or findings expressed are those of the author and should not be interpreted as representing the official views or policies of the Department of Defense or the U.S. Government.

Source: P. Bassirian, University of Virginia Source: M. Hanson et al, Computer 2009

Source: