Top Banner
ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti tradizionali
32

ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

Mar 27, 2015

Download

Documents

Devin Wilkinson
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Page 1: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

Strutture MEMS in un transceiver a radio frequenza

Potenziale applicativo dei MEMS include la sostituzione di componenti tradizionali

Page 2: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

Applicazione MEMS in sistemi wireless

Possibili elementi in un transceiver adatti a realizzazione MEMS: Induttori ad alto fattore di qualità integrati Capacitori variabili Interruttori accoppiati in DC o AC Micro-risonatori, per filtri o tank per oscillatori locali

Caratteristiche favorevoli dei nuovi componenti MEMS permettono di rivedere anche la descrizione del sistema a livello di architettura

In particolare: selezione di canale e riconfigurabilità…

Page 3: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

Componenti passivi ad alto fattore di qualità

Induttori integrati isolati dal substrato semiconduttivo hanno perdite ridotte maggiore fattore di idealità (Q)

Page 4: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

Interruttori MEMS accoppiati in DC o AC-RF

Deformazioni di strutture conduttive, tramite trasduzione elettrostatica od magnetica, si utilizza per implementare interruttori

Page 5: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

Strutture MEMS risonanti

Masse sospese elasticamente a punti di ancoraggio implementano strutture risonanti

Tramite trasduzione elettrostatica si possono trasferire caratteristiche di risonanza meccanica all’interno di un sistema elettrico

Utilizzabili a diversi range di frequenza, dai pochi KHz fino alle centinaia di MHz (GHz?..)

Filtri alle frequenze intermedie (IF in supereterodyne) fino alla selezione di canale (HF) o tank per LO…

Tipicamente alti fattori di qualità raggiungibili (~10000), grazie alle ridotte perdite meccaniche (in vuoto…)

Page 6: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

Strutture risonante a trasduttore comb-drive

Strutture a trasduzione trasversale basate sul comb-drive (pettine)

Capacità variabile linearmente con la deformazione elettrostatica

Trasduzione lineare

Page 7: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

Capacitori variabili integrati

Tramite strutture deformabili e trasduzione elettrostatica è possibile realizzare capacitori variabili MEMS integrati

Page 8: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

Esempio: ricevitore a banco di switch

Page 9: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

Simulation approaches for MEMS

System Level

Sub-system / Circuit Level

Device / Physical LevelTOP-DOWN

BOTTOM-UP

• System modeling• Behavioral analysis of complete MEMS devices

• Reduced order modeling• Electrical equivalent• Lumped elements• Modified nodal analysis

• 3D modeling• FEM / FVM / BEM field solvers• Coupled domains

Page 10: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

Sub-system / Circuit Level Modeling

This modeling level involves: Terminal characteristics description of a sub-system Multiple physical domains phenomena and quantities Hierarchy compatible model complexity

Reduced-order modelling approach: Starts from exact continuous 3D modelling; space

discretisation and reduction of mechanical degrees of freedom are applied

Usually requires expertise and intuition to avoid loss of significant device behaviour description

Lately some automated model reduction tools are available also from commercial CAD tools

Seems more appropriate to a bottom-up design methodology…

Page 11: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

Generalized Kirkhoffian networks

Kirkhoffian network theory is applicable to diverse energy domains, provided that: Flow (through) and difference (across) quantities can be identified,

with relationships between them given as implicit/explicit equations or differential equations depending only on terminal quantities and internal states. Conservation laws apply:

Zero sum of across quantity along a closed network loop Zero sum of through quantity into a node or network cut-set

Physical domain Flow quantity Difference quantity

Electrical Current Voltage

Mechanical-trans Force Velocity / Displ.

Mechanical-rot TorqueAng. Velocity /

Displ.

Pneumatic Volume Flow Pressure

Thermal Heat Flow Temperature

Page 12: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

Lumped element electrical equivalence

Different energy domains can have formally identical constituent relationships (implicit/explicit or differential)

extFxkxBxM ext

t

idvLR

vvC

1

geometry parameters

mech. model abstraction

energy domain equivalence:

force currentvelocity voltage

electrical simulation

NO DIRECT LINK WITH DESIGN PARAMETERS

Page 13: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

Higher level electrical equivalent approach

Equivalent electrical network modelling is suitable to small-signal analysis of generalised dumped resonators

Electrical equivalent extraction quickly looses track of geometrical and mechanical design parameters

Page 14: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

Hierarchical structural analysis approach

MEMS devices are made of basic shapes and elementary components, i.e. plate masses, beam springs, electrostatic air-gaps…

A number of connectivity points (nodes) and degrees of freedom (dof) established for each component

A global reference system allows for relative placement between components forming complete devices

Geometrical and mechanical design parameters are maintained visible throughout the modeling and simulation cycle

N1 N2

Nn N3

x1

x2xd…

x1

x2xd…

x1

x2xd…

x1

x2xd…

N1 N2

Nn N3

x1

x2xd…

x1

x2xd…

x1

x2xd…

x1

x2xd…

x1

x2xd…

x1

x2xd…

x1

x2xd…

x1

x2xd…

Page 15: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

Matrix-based structural analysis

Each component has a total complexity of m=n·d, where n equals the number of nodes and d the dof’s

Two vectors of dimension m are created for the through and for the across quantities:

In general, any linear physical behaviour of a component can be described by an mxm matrix , relating the forces/torques vector to the displacements vector or any of its derivatives, in the local reference system:

The three main physical descriptions are:i) Elasticity (structural analysis) stiffness matrix kii) Inertia (virtual works principle) mass matrix Miii) Damping (viscosity) damping matrix B

,...,,~~

UUUUUAS

UkUBUMS

mm UUSS 11 US

Page 16: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

Assumption of thin uniform cross-section, i.e. L>>w,t with L being the length of the beam

Homogeneous material: Young modulus E and Poisson ratio

Two connectivity nodes at the two beam’s ends, each one given six degrees of freedom: total model complexity of 12

Indexes are: axial (1,7); shear (2,3,8,9); bending (5,6,11,12); twisting (4,10)

Linear Euler beam – Definitions

twA

12;

12

33 twI

twI zy

22

3

7

2

tw

twJ

Area

Polar 2nd moment

Bending moments

Page 17: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

Linear Euler beam – Stiffness matrix [k]

21 kkkukS

L

EI

L

EIL

EI

L

EIL

GJL

EI

L

EIL

EI

L

EIL

AEL

EI

L

EIL

EI

L

EIL

GJL

EI

L

EIL

EI

L

EIL

AE

zz

yy

x

yy

zz

zz

yy

x

yy

zz

2000

60

02

06

00

00000

06

012

00

6000

120

00000

4000

60

04

06

00

00000

06

012

00

6000

120

00000

2

2

23

23

2

2

23

23

1k

L

EI

L

EIL

EI

L

EIL

GJL

EI

L

EIL

EI

L

EIL

AEL

EI

L

EIL

EI

L

EIL

GJL

EI

L

EIL

EI

L

EIL

AE

zz

yy

x

yy

zz

zz

yy

x

yy

zz

4000

60

04

06

00

00000

06

012

00

6000

120

00000

2000

60

02

06

00

00000

06

012

00

6000

120

00000

2

2

23

23

2

2

23

23

2k

The result is the complete stiffness matrix:

Page 18: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

Linear Euler beam – Mass matrix M

Analysis limited to translational inertia leads to:

140000

420

130

0140

0420

1300

006

000

0420

130

70

900

420

13000

70

90

000006

1105

000210

110

0105

0210

1100

003

000

0210

110

35

1300

210

11000

35

130

000003

1

2

2

2

2

LL

LLA

J

L

L

LL

LLA

J

L

L

AL

x

x

2M

105000

210

110

0105

0210

1100

003

000

0210

110

35

1300

210

11000

35

130

000003

1140

000420

130

0140

0420

1300

006

000

0420

130

70

900

420

13000

70

90

000006

1

2

2

2

2

LL

LLA

J

L

L

LL

LLA

J

L

L

AL

x

x

2M

21 MMM

Page 19: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

Spectre-HDL® language for MEMS simulation (1) Model interface at schematic level through nodes and parameters,

e.g. beam dimensions, orientation angles, …

symbol

spectreHDL

declarations

init

analog

post

schematic

externalparametersand nodes

internalparametersand nodes

symbol

spectreHDL

declarations

init

analog

post

schematic

externalparametersand nodes

externalparametersand nodes

internalparametersand nodes

internalparametersand nodes

SpectreHDL model structure: Declarations of nodes,

parameters (internal and external) and variables

init: initialization performed once before simulation

analog: model core, iterated at every simulation step

post: final computations after simulation converged

Page 20: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

Spectre-HDL® language for MEMS simulation (2) SpectreHDL allows for the definition of across and through

quantities, adopting a Cartesian reference system: “across” displacements (x,y,z) and rotations (x,y,z) “through” forces (Fx,Fy,Fz) and torques (x,y,z)// Structural analysis implementation within SpectreHDL

// Roberto Gaddi, 29/01/2002// Quantity definitions for the mechanical signals// For each signal, name, units and absolute tolerance is given

displacement quantity name="disp" units="m" abstol=1pforce quantity name="frc" units="N" abstol=1pvelocity quantity name="vel" units="m/s" abstol=1n blowup=1e12angular_velocity quantity name="avel" units="rad/s" abstol=1n blowup=1e12angle quantity name="ang" units="rad" abstol=1ptorque quantity name="trq" units="Nm" abstol=1pacceleration quantity name="acc" units="m/s2" abstol=1u blowup=1e15angular_acceleration quantity name="aacc" units="rad/s2" abstol=1u blowup=1e15voltage_derivative quantity name="DV" units="V/s" abstol=1p blowup=1e15

Two key simulation parameters must be properly adjusted due to several orders of magnitude differences among electrical and mechanical quantities:

abstol : absolute tolerance during simulation blowup : critical value that defines a diverging simulation

On top of them also velocity and acceleration, both translational and angular, are declared as across quantities

Page 21: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

MEMS component library in Cadence®

Basic components implemented so far:

Straight beam12 degrees-of-freedom, elasticity, viscous

damping, inertia, electric conductivity

Rigid plate mass6 degrees-of-freedom, viscous damping, inertia,

contact detection

Suspended plate capacitor

4 degrees-of-freedom, electrostatic force, charge storage, viscous damping, inertia, contact forces

Rigid comb-drive actuator

4 degrees-of-freedom, electrostatic force, charge storage, viscous damping, inertia

Anchor points – Stimulus forces

6 degrees-of-freedom, stimuli for large and small signal static and dynamic analysis

Page 22: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

MEMS component library in Cadence®

Page 23: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

Prediction of beams eigenfrequencies

F1=173.9KHz

F2=1.088MHz

F3=3.039MHz

Page 24: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

Resonance modes of a composite device (1)

res1=110kHz res2=225kHz

res3=275kHz res4=350kHz

Page 25: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

Resonance modes of a composite device (2)

Small-signal ac simulation of the device with a punctual force stim.

res1=109kHz

res2=204kHz

res3=278kHz

res4=347kHz

Page 26: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

Complete MEMS example: tunable capacitor

MEMS varactor with T-shaped spring suspensions

Parasitic extraction from RF characterisation or electromagnetic simulations should be performed for accurate RF modelling

Here only access resistance due to finite conductivity of beams is accounted for

Page 27: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

MEMS Varactor top-down design (1)

Critical specs for varactor as tuning element within an electronic circuit are: tuning ratio (Cmax/Cmin), nominal capacitance (Cnom) and pull-in voltage (VPI)

Vbias

Z-pos

Vbias

Z-pos All geometrical parameters are available for design: MEMS design tool based on Spectre simulator

Parametric static (DC) simulations quickly allow for Pull-in voltage design

Page 28: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

MEMS Varactor top-down design (2)

The tuning ratio is technology defined

A sweep from 200x200m2 to 400x400m2, at f=1.8GHz and bias voltage VNOM

ox

oxairox

t

tg

C

C

min

max

Total plate area A and nominal voltage VNOM define the capacitance value Cnom

Small signal (ac) analysis performed at given frequency and sweeping A leads quickly to the desired nominal capacitance

AA~

Page 29: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

MEMS Varactor top-down design (3)

Spring beams dimensions control the overall spring constant k, e.g. the pull-in voltage

Access resistance also depends on beams W/L Possible trade-off: tuning range vs. resistive losses

width: tuning range Q factor

Page 30: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

Varactor transient behaviour

Transient simulations can give insight to response time to VBIAS

Spectre® simulator does not show any convergence issues, even with added electronics

Both electrical and mechanical quantities can be observed

Page 31: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

Varactor insertion within an LC tank

Typical application can be the tuning element within an LC tank for an RF voltage controlled oscillator (VCO)

LC network includes two varactors that provide isolation from controlling voltage

Page 32: ARCES - University of Bologna Strutture MEMS in un transceiver a radio frequenza Potenziale applicativo dei MEMS include la sostituzione di componenti.

ARCES - University of Bologna

Mixed-domain complete VCO simulation

Differential VCO: CMOS technology from UMC, 0.18m channel length

Model library based on BSIM3 model Spectre achieves convergence in

transient analysis Periodic-steady-state (PSS) simulation

for noise analysis still have issues…

time

Vout

time

Vout