catherine dehollain epfl, lausanne, switzerland

LOW POWER REMOTELY POWERED SENSOR NETWORKS AND RFIDS FOR MEDICAL AND TELECOMS APPLICATIONS

POWER AND DATA TRANSMISSION FOR MEDICAL AND TELECOMS APPLICATIONS

CATHERINE DEHOLLAIN

EPFL, LAUSANNE, SWITZERLAND

[email protected]

RFIC.EPFL.CH

5TH JUNE 2015, PAVIA, ITALY

5TH JUNE 2015, PAVIA, ITALY3rd February 2016

Content2

C. Dehollain, EPFL, Lausanne

PART 1: ARCHITECTURES OF REMOTELY POWERED SENSOR NETWORKS

PART 2: PASSIVE TRANSMITTERS FOR REMOTELY POWERED SENSOR NETWORKS


5TH JUNE 2015, PAVIA, ITALY

PART 1: ARCHITECTURES OF REMOTELY POWERED SENSOR NETWORKS

3



At the boundary between different domains4

New architectures of sensor nodes for wireless communications at short distance Back-scattering/ Load modulation (e.g. RFIDs), Impulse Radio Ultra Wideband (IR UWB),

Super-regenerative transceivers, Direct conversion transceivers. Biomedical field: implants, wearable sensor networks.

Remotely powered wireless circuits Through RF wave by magnetic coupling , electro-magnetic coupling, electro-acoustic

coupling (ultrasound). Rechargeable micro-batteries.

Ultra low-power wireless communications Low supply voltage imposed by advanced technologies, ultra-low current operation

MHz to GHz-range ICs RF models of the transistors and passive elements, parasitic coupling.

Fully integrated solutions RF and Mixed-mode circuits. Circuits in advanced CMOS technologies. Integrated tuning elements, MEMS (Micro Electro Mechanical Systems).


Data Transfer Methods5

One single frequency for remote power and data communication Simple transmitter in the sensor node (load modulation or backscattering) Interruption of the transfer of power during data transmission Optimisation of the link for power transfer and data communication thanks to

trade-off

Dual frequency approach: one frequency for data communication and another frequency for remote power Power transfer is independent of data communication Extra power is required due to the active transmitter of the sensor node Extra antenna is used for data communication


Backscattering Modulation in far field6

One single frequency for remote power and data communication Harry Stockman, "Communication by Means of Reflected Power”, 1948 The tag is tracked if the main station (reader or interrogator) is in range Minimization of the power consumption of the tag → Generation of the

carrier at base station and backscattering of the incident wave


U. Karthaus and M. Fischer, “Fully integrated passive UHF RFID transponder IC with 16.7 μW minimum RF input power,”Solid-State Circuits, IEEE Journal of, vol. 38, pp. 1602–1608, Oct. 2003.J. Curty, Analysis and optimization of passive UHF RFID systems. PhD thesis, EPFL, March 2006.

Load Modulation in near field7

G. Yilmaz, Wireless power transfer and data communication for intracranial neural implants, EPFL, PhD thesis, Dec. 2014.

One single frequency for remote power and data communication


The carrier is generated in the tag. LC OOK Transmitter. The frequency of the carrier is

determined by the LC tank.

Wireless Active Transmitter for Data Communication8


Inductive Coupling (Near-Field) Near field region → d < λ/2π Typical frequency bands: 125 kHz, 6.78 MHz, 13.56 MHz Effective operation distance of 10 cm in air Highly sensitive to misalignment between the primary coil and the

secondary coil of the transformer Higher energy efficiency in short distance at d<10 cm

Electro-magnetic Coupling (Far-Field) Far field region: → d > λ/2π Typical frequency bands: 868 MHz, 915 MHz, 2.45 GHz, 5.8 GHz. Effective operation distance up to 15 m in air Higher data rate than the near-field systems

Wireless Remote Powering9


Single Frequency for Remote Power and Data Communication

10


Dual Frequency for Remote Power and Data Communication

11

→ Three fundamental units1. Implantable sensor system2. External base station for data communication and remote powering 3. Long distance data communication for data base and reporting


Knee prosthesis monitoring by inductive coupling


O. Atasoy, C. Dehollain, IEEE NEWCAS Conf. 2012, PRIME Conf. 2010, PRIME Conf. 2013, IEEE Trans. on Automation 2013O. Atasoy, PhD thesis n0 5992, EPFL, November 2013

Objectives• Transcutaneous powering by inductive link• Data communication between the

prosthesis and the external reader

Challenges• Low coupling factor of inductive link due to

distance between the two coils and limitedantenna size

• High power requirement (10 to 20 mW)

Goals• Increase of the life expectancy of the

prosthesis• Monitoring of the force, of the movement of

the knee and of the temperature

Swiss SNF NanoTera

Simos Project

12

Ultrasonic Remote Powering and Communication13


European FP7 project: www.ultrasponder.org

F. Mazzilli, C. Lafon, C. Dehollain: EMBC Conf. 2010, ISCAS Conf. 2012, IEEE TBioCas Journal 2014, BioCAS Conf. 2014, IEE Electronics Letters 2016F. Mazzilli, PhD thesis no 5631, EPFL, March 2013

Digestive Track Diagnostic14

CTI Swiss Project

→ Diagnosis of digestive system for:• Constipation• Irritable Bowel Syndrome (IBS)• Gastroparesis

→ 3D trajectory information of the pill through the gastrointestinal track.

→ The pill provides three axis magnetic field for location information.

→ Fully integrated ASIC development enables miniaturization of the pill.

J.L. Merino, C. Dehollain: ICECS 2012, ISMICT 2013, ISCAS 2015


Passive Memory Tag for High Data Rate15

Goal: to obtain a medium operating range between the interrogator and the passive memory tag for a given RF output power of the interrogator and a high data rate

System Specifications: • Read/write data rate: 10Mbit/s• Distance range: 10 to 20 cm

• VDC < 3V, IDC < 3mA • Data Communication: 2.4GHz ISM)• Remote powering: 0.9GHz (ISM)

European IP Project MINAMI (2006 - 2010)

N. Pillin, N. Joehl, C. Dehollain, M. Declercq, RFID Conf. 2008, PRIME Conf. 2009, IEEE Trans. on Circuits and Systems-I 2010 N. Pillin, PhD thesis no 4616, EPFL, March 2010


16


Magnetically-Coupled Remote Powering System for Freely Moving Animals

Magnetically-Coupled Remote Powering System for Freely Moving Animals

17

• Real-time long-term monitoring Continuous remote powering• Condition of subject is important in order to obtain reliable

measurement results• Conscious Awake (without anesthetized)• Non-stress environment Freely moving

k

L1 L2

Reader Coil

Tag Coil

Reader Side Tag Side

Power

DataReader Tag

General RFID concept Scenario for remotely powered systems


Specs for Freely Moving Laboratory Rodents18


Application: Multi-bio sensor monitoring Condition of animal: mobile/awake Fully implantable sensor node Weight: Less than 2 g (less that 10%) Volume: Less than 1 cm3

Maximum power consumption: 2 mW Wireless Power Transfer Remote powering distance: 3 cm Data communication data rate: 100 kbit/s Data communication distance: 40 cm

SIZE FREE MOVE

Remote Powering

Data Comm.

Implantable Bio-Monitoring System19

Conceptual design of battery-less implantable multiple sensor system

Targets • Detection of different drugs• Measurement of pH and temperature• Detection of different endogenous compounds

Problems • Size and weight to be implantable• Low coupling factor due to distance & tissue

Continuous and Long-term monitoringSwiss SNF Sinergia Project


E. G. Kilinc, F. Maloberti, C. Dehollain: IEEE SM2ACD 2010, ISCAS 2012, BIOCAS 2012, NEWCAS 2013, IWASI 2013, ICECS 2013, BIOCAS 2014, MWSCAS 2014, IEEE Sensors Journal 2014, IEEE TBioCasJournal 2015, IEEE Sensors Journal 2015, Springer book 2016E.G. Kilinc, PhD thesis n0. 6105, EPFL, Feb. 2014

Temperature Measurements20

To monitor local temperature of the brown adipose tissue of the mouse to study its metabolism.


Metabolism Study21


Temperature Sensor in Brown Adipose Tissue• Metabolism study• Inflammation • Wireless powered sensor

Temperature sensor

22


Features• Small tip diameter (Ø0.5mm Max.) • High sensitivity• Temperature range: -40˚C to +125˚C• Rapid time constant

Applications• Laboratory animal research• Temperature control for bath shower• DNA research sensors• Medical implants

Sensor Parameters Value

Resistance@+25˚C (kΩ) 100

Response time in liquids (ms) 200

Dissipation constant in still air (mW/˚C)

0.3

Resistive Response (Ω/0.04˚C) 178.5

Micro-BetaCHIP Thermistor Probe


Thermistor Response Curve23

100K6MCD1, BetaTHERMSensors

Target temperature range: 27 °C to 42 °C Target resolution: 0.05 °C to 0.1 °C

C. Dehollain, EPFL, LausanneC. Dehollain, EPFL, Lausanne

Time-domain Sensor Readout24

The sensor response is directly digitized by a time-domain comparator to achieve ultra-low-power operation.

M. A. Ghanad, M. M. Green, and C. Dehollain: ICECS 2012, A-SSCC 2013, NEWCAS 2013, IEEE Transaction on Circuits and Systems I 2014, IEE Electronics Letters 2014, ISCAS 2015, ESSCIRC 2015M.A. Ghanad, PhD thesis n0. 6253, EPFL, Oct. 2014


Implemented Data Transmitter25

Spec. Value

Center freq. 868 MHz

Modulation OOKPower 144 uWSupply 1.3 V

Data-rate 1.7 Mbps

Turn on time < 10 nsFreq. drifts < 1 MHzTechnology 0.18 um

LC cross-coupled pair oscillator Frequency determined by C1, C2 and the off-chip inductive antenna Resistive loss compensated by the negative resistance of the two MOS

cross-coupled pairs

Loop Antenna26

is the wave length of the radiated signal

J. Pandey et al., “A fully integrated RF-powered contact lens with a single element display,” Biomedical Circuits and Systems, IEEE Transactions on, vol. 4, pp. 454–461, Dec. 2010.

If it is assumed that the antenna is isotropic, which means that it radiatesthe same intensity in all directions, then the gain of the antenna GT can beapproximated by the efficiency ant

Low-power Implantable Chip

High efficiency semi-active rectifier Time-domain resistance to digital converter Time interleaved sensor readout and data transmission

27


Local Temperature Sensing Implantable Chip28

SensorReadout

DigitalOsci.Rectifier

1480 um

690

um Regu

lato

r

V REF

Gen

.

MOS Cap.

MOS Cap.MOS Cap.

Semi active rectifier with leakage current control. Time-domain sensor readout. Duty cycled free-running oscillator for data communication.Power Consumption is 6X better than the similar reported works.

M. A. Ghanad, M. M. Green, and C. Dehollain, “A Remotely Powered Implantable IC for RecordingMouse Local Temperature with ±0.09 °C Accuracy,” IEEE A-SSCC 2013 (Asian Solid-State Circuits Conference).


Friis propagation equation29

The Friis equation is valid for far field operation (<< d) n = Path loss exponent = 2 in free space.

Normally n is chosen between 2 to 4 depending on the environment.

d = Distance between the transmitter and the receiver GR = Antenna gain of the receiver GT= Antenna gain of the transmitter PR = Power available at the input of the receiver antenna PT = Transmitter power

Data Communication Frequency Planning30

Wong et al., “A 1 V wireless transceiver for an ultra-low-power SoC for bio telemetry applications,” IEEE Journal of Solid-State Circuits, vol. 43, pp. 1511–1521, July 2008.

Power transfer ratio = 10log (PR/PT)

868 MHz

2400 MHz433 MHz

31


Wireless Power and Data Transfer for Intracranial Epilepsy Monitoring

Intracranial Neural Implants

• Macro iEEG electrodes• 10 mm diameter• 10 mm separation

• Data extraction• Cable bundles• Amplification and

processing outside

32

J. Van Gompel et al., Neurosurgical Focus, vol. 25, no. 3, p. E23, Aug. 2008.

Drawbacks of Current iEEG

Risk of Cerebrospinal Fluid (CSF) leakage Risk of CSF infection Reduced patient comfort Short monitoring period

33

34


Scenario proposed by EPFL

SNF Swiss Project


35


• EPFL news on 9th Feb 2015: http://actu.epfl.ch/news/monitoring-epilepsy-in-the-brain-with-a-wireless-s/• PhD Thesis n0 6947, Author: Gurkan Yilmaz, EPFL, December 2014.• G. Yilmaz, O. Atasoy, C. Dehollain, «Wireless energy and data transfer for in-vivo epileptic focus localization», IEEE

Sensors Journal 2013, IWASI 2013, NEWCAS 2014, BIOCAS 2014, Microelectronics Journal Elsevier 2014.

Wireless Power Transfer by Magnetic Coupling at 10 MHz10 mW delivered power with 36% power efficiency from 1cmImplanted coil size < 15 x 15 mm235% power efficiency in in-vitro testsPolymer based packaging and modeling of the packagingAt least 1 month of successful in-vitro operation


36

Wireless Data Communication (single frequency approach) Load modulation on the power transfer frequency 1Mbps on 8.4 MHz carrier has been realized (BER < 10-5) 33% power efficiency in in-vitro experiments

Wireless Data Communication (dual frequency approach) A 433 MHz active transmitter has been designed 1.8 Mbps has been realized (BER < 10-5) Base station in discrete components


in-vitro tests (single frequency)

Transmitterat 433 MHz

0.18um CMOS

37


Far-Field Remotely Powered Wireless Sensor System at 2.45 GHz

Wireless Remotely Powered Sensor System at 2.45 GHz

38


RECTIFIER FOR REMOTE POWERING at 2.45 GHz

Integrated Sensor System39


O. Kazanc, J.A. Rodriguez-Rodriguez, M. Delgado-Restituto, F. Maloberti, C. Dehollain, IEEE NEWCAS Conf., June 2013

Matching with Programmable Capacitors

Adaptive Impedance Matching40


Before Calibration After Calibration

O. Kazanc, F. Maloberti, C. Dehollain, IEEE WiSNet Conference, Jan. 2013

Performance Summary41


Performance Metric Value

Wireless Comm. Freq. 2.45 GHz

VDD (A & D) 1.5 VPower Consumption 20 μW

Data Rate 125 kbits/sSensor Accuracy ~ 0.05 °C

Area 2.25 mm2

• PhD Thesis n0 6152, Author: Onur Kazanc, EPFL, June 2014.• O. Kazanc, F. Maloberti, C. Dehollain: ISMICT 2011, ISCAS 2012, NEWCAS 2013, BioWireless 2012, WiSNet 2013

EMBC 2014.

42


Far-Field Remotely Powered Wireless Sensor System at 868 MHz

Passive UHF RFID Tags43

Capacitive Humidity Sensor Oscillator Based Sensor Readout Back-Scattering Wireless Com. Remote Powering Link

Base Station Base Station Antenna Tag Antenna Rectifier

Low Power Analog Circuitry Supply Generation

Low Drop-Out Voltage Regulator Bandgap Reference

Current Reference


Rectifier

Modulator

Hum

idity

Sen

sor

Tag IC

MatchingNetwork

POR

Ant

enna

SensorInterface

Electro-Magnetic Remote Powering44

Base Station Antenna Patch Gain = 3.6 dB S11 = -24 dB @ 866 MHz

Tag Antenna Inductively Coupled Meandered Dipole Gain = 1.2 dB Impedance matched to chip impedance

Rectifier Differential Threshold voltage cancellation PCE = 65% measured

-15

-10

-5

0

5

30

60

90

120

150

180 0

PatchTag

vRF+

vRF-

RLCS

CC CCCC

CI VDCCI

CC CCCC

K. Kapucu, C. Dehollain, IEEE ICECS 2013, IEEE RFID-TA 2014

Low Power Sensor Interface45

Capacitive sensor Printed humidity sensor

Sensor readout Supply voltage

Down to 0.8 V Low power

12 µW @ 0.8 V UMC 0.18 µm CMOS

Distance range: 4 m 3.3 W EIRP from the base station

EPFL, Lausanne

PhD Thesis n0 6540, Author: Kerem Kapucu, EPFL, April 2015.K. Kapucu, J.L. Merino, C. Dehollain, PRIME 2013 and ICECS 2013K. Kapucu , C. Dehollain: PRIME 2014, RFID-TA 2014, RFID 2015, IWASI 2015



5TH JUNE 2015, PAVIA, ITALY5TH JUNE 2015, PAVIA, ITALY

PART 2: PASSIVE TRANSMITTERS FORREMOTELY POWERED SENSOR

NETWORKS

46


Backscattering Data Communication

47


The RF carrier is generated in the interrogator also called reader The tag, also called transponder, modulates and reradiates the RF carrier that is

coming from the interrogator when there is a high impedance mismatch The power consumption of the tag is minimised because it does not include a RF

oscillator to generate the carrier

IncomingWave

BackscatteredModulated

Signal

Interrogator Tag

f0- fD f0 f0+ fD

Principle of the Backscattering Data Communication

48


fo: carrier frequencyfD: data frequency

If Data = Bit “1” Zin = R’ is mismatched to the tag antenna All the power of the RF incoming signal is reflected to the interrogatorIf Data = Bit “0” Zin = R is matched to the tag antenna All the power of the RF incoming signal is absorbed by the tag

R'

R

Data

f0- fD f0 f0+ fD

49


Principle of the Backscattering Data Communication

D A T A

R

R

DATA

Series impedance switcher Parallel impedance switcher

Examples of Input Impedance Switcher50


IncomingWave

BackscatteredModulated

Signal

Interrogator Tag

DATADemodulator

PowerSplitter

RF Oscillator

RF Band-PassFilter

Mixer

DATADemodulator

PowerSplitter

RF OscillatorRF

Band-PassFilter

Circulator

Mixer

f0- fD f0 f0+ fD

Architecture of the Reader (Interrogator)

51


f0-fc+ fDf0-fc

f0-fc-fD f0+ fc+ fDf0+ fc

f0+ fc-fDf0

D A T AM o d u la to rIm p e d a n ces w itc h e r

IF O s c illa to rM o d u la te dD a ta

Intermediate Frequency (IF) Backscattering Data Communication

52


fo: carrier frequencyfC: IF frequency

fD: data frequency

• Amplitude

The reflection coefficient at the tag-antenna interface can vary in

• Phase

• Two basic binary modulation types are possible: ASK & PSK

• Power available for both tag power supply & for data communication

• Data communication quality (Bit Error Rate: BER)

• They must be compared in terms of

Modulation Types53


RANT L

matchingAnt. tag

Ri

Ci

I

(switch closed)

Ri (switch open)Tag input

impedance

Reflected power dueTo mismatch at the tag

Time

Dut

y-cy

cle

ASK

stan

dard

ASK

bit

stre

am

Reflected ASK modulated signal

DC

Bit « 1 »: the switch is closedBit « 0 »: the switch is open

ASK Modulation54


RANT L

React.Ant. tag

Ri

CiB A

C0

1 0 1 0

Tag input impedance at B

Z1

Z0XC + XC'

XL

1

L

1

0

State 1The switch is closed

State 0The switch is open

In B: Absorbed power and reflected power are constant

In A: Voltage at tag input is however not constant

PSK Modulation55


Bit Error RateBER = 10-4 1 bit is not correct over 10’000

Comparison through the Bit Error Rate (BER)Eb = Average Energy per bitN0 = Noise level at receiver input = Ri / RANT

Q = tag input series quality factor = 1/(Ri.Ci) DC = Modulation Duty Cycle

J.P. Curty, M. Declercq, C. Dehollain, N. Joehl: « Design and Optimization of Passive UHF RFID Systems » , Editor Springer, year 2007, ISBN: 0-387-35274-0.

Performance of ASK / PSK Modulations 56


BER

Optimal ASK and PSK BER comparison(ASK: DC = 100%, = 1 and PSK: = 1, Qin = 5.6)

Eb /N0

57


Performance of ASK / PSK Modulations

Ref

lect

ion

coef

ficie

nt

Impedance Matching = 0 and = 1

Normalized resistance = Ri / Rant

The input capacitance is equal to a few hundreds fF

Reflection coefficient is close to ±1 according to the position of the switch

RANT L

tag

Ri

Ci

Priority to communication distance

The real part of Ri is very high (»1k) and much higher than Rant

58


Reflection Coefficient

L and Ci resonate at the operating frequency

Reflection coef. = (Ri – Rant) / ( Ri + Rant) = ( – 1) / ( + 1)

Pseudo PSK Modulation

Ri is much larger than RANT

Voltage at rectifier input is higher than in impedance matchingcondition so that the rectifier has enough input voltage to operate

Absorbed power is lower than in impedance matching condition Modulation corresponds to nearly a 180° phase shift of the

reflection coefficient Pseudo PSK Modulation

RANT

L Ri

C

Zin

59


Nor

mal

ized

pow

er w

ave

ampl

itude

%

Time

Power waves for both modulation states

60


It is important to take care of direct-coupling effect

61


Basic Architecture of the Reader

osc

DATA RX

IF

RSSI

LNA

DATA TX

PA

C

90°

0°

LNA

AGC

OOK

Amplitude OOK ModulationOOK IQ Demodulation

62


Improved Architecture of the Reader62

Read Range of passive far field RFID systems

• The phase noise of the local oscillator in the reader has an important impact• A model is derived to estimate the read range of passive far-field RFID systems

PRIME Conference, N. Pillin, C. Dehollain, M. Declercq, Cork, July 2009

63


64


Radar Cross Section

Tag antenna switches between two different Radar Cross Section called RCS: σ1 and σ2

Effective tag antenna RCS is expressed by:

Model

Gt: gain of the antenna of the tag Gr: gain of the antenna of the reader : conversion loss factorσi : effective tag antenna RCS CTx/Rx: coupling factorN (fsb, B): integral of the phase noise on the bandwidth BSNRmin: minimum required SNR at the input of the reader: wave length of the RF signal

65


66


Measurements

Measurements compared to Model

Measurements were achieved on a laboratory reader/tag system at 900 MHz and 2.45 GHz to verify the model.

PRIME Conference, N. Pillin, C. Dehollain, M. Declercq, Cork, July 2009

67


Radio Regulations

Some regulations are fine for wireless power transfer (high Tx power) Others for communication (large frequency bandwidth)

(1~3.3 W EIRP, 2for indoor use)

68


Passive Memory Tag

European IPProject MINAMI

• Contain high capacity non volatile memory• Can store multimedia content• New distribution method for– Videos– Music– Images

69


Compatible with Non Volatile Memory (NVM)FRAM : 7 mW @ 10 MbpsTotal consumption (IC + memory): 10 mWTag IC realized in a standard 0.18um CMOS processRectifier efficiency: 40%

Passive Memory Tag

Read/write data rate: 10 Mbit/sMinimum Distance range: 15 cm

70


Dual Frequency Tag

SPECIFICATIONSDistance Range: 0.15 mData Rate: 10 Mbit/sPower Consumption: 10 mW

Data Rate: 10 Mbit/s Minimum Frequency Bandwidth = 10 MHzRF Frequency for data transmission: 2.4 GHz to 2.485 GHz

Power Consumption: 10 mW Mini Pav = 25 mW for rectifier power efficiency = 0.4

Friis : Peirp = 3.3 W, Gr = 1, d = 0.15 m, f = 868 MHz Pav max = 102 mW: OKFriis: Peirp = 4 W, Gr = 1, d = 0.15 m, f = 2.4 GHz Pav max = 16.2 mW: Not OK

IT IS NECESSARY TO HAVE A DUAL FREQUENCY TAG: 0.87 GHz, 2.4 GHz

PAV S.2

4.GR PEIRP .GR .

2

4d 2

Medium operating range High data rate between the reader and the tag

71

Friis propagation equation


Chapter 7 of PhD thesis, No 4616, N. Pillin, year 2010, EPFL

72


Dual Frequency Tag

Process: UMC CMOS 0.18m Area: 1.5 mm x 1.5 mm

with I/O pads Dual frequency, passive RFID tag

can be read at 10 Mbps at 33 cm Rectifier’s power efficiency: 36% Tag detector/ receiver can operate

at 10 Mbps in read mode

73


Dual Frequency Tag

Chapter 7 of PhD thesis, No 4616, N. Pillin, year 2010, EPFL

• Different backscattering modulation methods have beencompared• ASK Modulation• PSK Modulation• Pseudo-PSK Modulation

• A model has been defined and validated to estimate theread range of passive, far-field RFID systems

• Depending on the specifications, it can be necessary toimplement a dual frequency architecture.

Summary on Backscattering Modulation74


Summary on remotely poweredsensor networks

75

Research spans Circuit development for low power consumption New architectures for wireless systems Utilization of wireless energy sources, i.e. magnetic,

electromagnetic, ultrasound, etc.Aiming scientific innovation and assisting medicine through various applications

Research in RFIDs Implantable Wireless Sensor Systems Radio Frequency Integrated Circuits


catherine dehollain epfl, lausanne, switzerland

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