Reconfigurable Ultra Low Power LNA for 2.4GHz Wireless Sensor Networks
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Reconfigurable Ultra Low Power LNA for 2.4GHz Wireless Sensor Networks. TarisT., Mabrouki A., Kraïmia H., Deval Y., Begueret J-B. Bordeaux, France . OUTLINE. Context RF Front End Specifications Circuit design Conclusion & Perspectives. OUTLINE. Context RF Front End Specifications

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Reconfigurable Ultra Low Power LNA for 2.4GHz Wireless Sensor Networks

TarisT., Mabrouki A., Kraïmia H., Deval Y., Begueret J-B.

Bordeaux, France


Outline
OUTLINE Sensor Networks

  • Context

  • RF Front End Specifications

  • Circuit design

  • Conclusion & Perspectives


Outline1
OUTLINE Sensor Networks

  • Context

  • RF Front End Specifications

  • Circuit design

  • Conclusion & Perspectives


Context
Context Sensor Networks

MicroElectronicMilestones

  • Computers in the seventies

    • Low cost Si technologies

    • Digital processing

  • The Cellular phone in the 90’s

    • Telecommunication network

    • RF circuits and systems

  • Wireless Sensor Network & RFID in the early 21th century

    • Gate reduction

    • Energy (scavenging, management…)


Context1
Context Sensor Networks

Wireless Sensor Network Configuration

  • Reduce the node power consumption…

Wireless Sensor Network

B

A

RF link 1

C

RF link 2

…by matching the RF link budget to the communication scenario


Outline2
OUTLINE Sensor Networks

  • Context

  • RF Front End Specifications

  • Circuit design

  • Conclusion & Perspectives


Rf front end specifications
RF Front End Specifications Sensor Networks

Node Top-down

  • Node at system level

Memory

RF Link Budget 2

µController

ADC

Sensor

RF Tx/Rx

  • Node Rx at system level

RF Link Budget 1

NFRx2

Power unit

PRx

RFFE

Demodulator

NFRx1

SNRdem

NFRx = PRx - SNRdem+(174-10 log BW)


Rf front end specifications1
RF Front End Specifications Sensor Networks

RF Link Parameters

BFSK modulation

Channel Characteristic

Attenuation L(R)

PTx

PRx

BER~10-3

distance R

node B

node A

SNRdem~10 dB

BW = 10MHz

NFRx= PRx– SNRdem+ (174-10 log BW)

PRx = PTx - Lpath(R)

2.4 GHz ISM Band


Rf front end specifications2
RF Front End Specifications Sensor Networks

RFFE and NF specification

  • Node Rx at system level

NFRx2

PRx

RFFE

Demodulator

NFRx1

SNRdem

  • RFFE and system specification

Mixer

LNA

NFRx2

LO

NFRx1

NFRxismainlysupported by the LNA !


Rf front end specifications3
RF Front End Specifications Sensor Networks

RFFE and NF specification

  • Node Rx at system level

NFRx2

PRx

RFFE

Demodulator

NFRx1

SNRdem

  • RFFE and system specification

Mixer

LNA

NFRx2

LO

NFRx1

NFRxismainlysupported by the LNA !


Outline3
OUTLINE Sensor Networks

  • Context

  • RF Front End Specifications

  • Circuit design

  • Conclusion & Perspectives


Circuit design
Circuit Design Sensor Networks

Low Power RF Metric

Optimized biasing!

  • Optimization of RF performances versus power consumption in the transistor…

RF skills

Current consumption

…by maximizing the FOMLP

Vth

~ Vth+ 100mV


Circuit design1
Circuit Design Sensor Networks

Amplifier Configurations

  • To compensate for the low gm in MI region…

Id

Id

Id

MP

MP

MP

bias

OR

?

RF

RF

RF

out

in

out

out

MN

MN

MN

in

in

Single Transistor Stage (STS)

Self Biased Inverter (SBI)

…active load configurations are preferred!


Circuit design2
Circuit Design Sensor Networks

Amplifier Configuration

  • Comparison of the Gain BandWidth (GBW) product…

30

Self Biased Inverter (SBI)

20

Gain (dB)

10

Single Transistor Stage (STS)

Frequency (Hz)

0

100G

1G

10G

GBWSTS

…the one of self biased inverter is the largest !

GBWSBI


Circuit design3
Circuit Design Sensor Networks

LNA topology

LNA 2.4GHz – CMOS 0.13µm

0.8V

VDD

Digital Control

3

VCC

DAC

Id

Cdec

Lpk

50 @ 2.4GHz

Off-chip

M2

Cm2

Rin/buffer

RF

out

50 @ 2.4GHz

M3

Cm3

Lg

Cl

Cm1

in

M1

Rpol2

Rpol1

Vpol2

Vpol1

Currentreuse

with feedback

buffer

LNA core


Circuit design4
Circuit Design Sensor Networks

Post Layout Performances

S21

NF

900µm

S11

700µm


Outline4
OUTLINE Sensor Networks

  • Context

  • RF Front End Specifications

  • Circuit design

  • Conclusion & Perspectives


Conclusion perspectives
Conclusion & Perspectives Sensor Networks

System Considerations

  • Match the radio performances with the RF link budget to reduce the power consumption of nodes in WSN

  • A matter of Noise Figure/Gain reconfiguration in the LNA

Requirement

Circuit analysis

  • Best tradeoff between RF skills and current consumption in MI region

  • Select the topology providing the largest GBW

Good

agreement


Conclusion perspectives1
Conclusion & Perspectives Sensor Networks

Done

Next step

NFRx2

NFRx1

Last step

  • A mixer to be designed in MI region

    • Gilbert Cell with current bleeding topology

Mixer

LNA

LO

  • A VCO with low power techniques

    • Negative resistance topology



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