Shelley Begley Application Development Engineer Agilent Technologies

Shelley BegleyApplication Development EngineerAgilent Technologies

Electromagnetic Properties of Materials: Characterization at Microwave Frequencies and Beyond

Definitions

Measurement TechniquesParallel Plate Coaxial Probe

Transmission Line and Free-Space Resonant Cavity

Summary

Agenda

DefinitionsPermittivity is a physical quantity that describes how an electric field affects and is affected by a dielectric medium and is determined by the ability of a material to polarize in response to an applied electric field, and thereby to cancel, partially, the field inside the material. Permittivity relates therefore to a material's ability to transmit (or "permit") an electric field…The permittivity of a material is usually given relative to that of vacuum, as a relative permittivity, (also called dielectric constant in some cases)….- Wikipedia

DkDkDfDf

'r 'r "

r"r

Permittivity and Permeability Definitions

interaction of a material in the presence of an external electric field.

"'

0

rrrj

Permittivity (Dielectric Constant)

Permittivity and Permeability Definitions

interaction of a material in the presence of an external electric field.

"'

0

rrrj

Permittivity (Dielectric Constant)

DkDk

Permittivity and Permeability Definitions

interaction of a material in the presence of an external electric field.

"'

0

rrrj

"'

0rr j

interaction of a material in the presence of an external magnetic field.

Permittivity (Dielectric Constant)

Permeability

DkDk

Permittivity and Permeability Definitions

interaction of a material in the presence of an external electric field.

"'

0

rrrj

"'

0rr j

interaction of a material in the presence of an external magnetic field.

Permittivity (Dielectric Constant)

Permeability

DkDk

"'rrr j "'

rrr j

Electromagnetic Field Interaction

Electric Magnetic

Permittivity Permeability

FieldsFields

STORAGE

MUT

STORAGE

"'rrr j "'

rrr j

Electromagnetic Field Interaction

Electric Magnetic

Permittivity Permeability

FieldsFields

STORAGE

LOSS

MUT

STORAGE

LOSS

Loss Tangent

'

"

tanr

r

'

"

tanr

r

CycleperStoredEnergy

CycleperLostEnergy

QD

1tan

CycleperStoredEnergy

CycleperLostEnergy

QD

1tan

Dissipation FactorDD

Quality FactorQQ

r

'r

''r

DfDf

Relaxation Constant

= Time required for 1/e of an aligned system to return to equilibrium or random state, in seconds.

cc f

2

11

cc f

2

11

11

10

100

10 100

Water at 20o C

f, GHz

most energy is lost at 1/

'r'r

"r"r

js

1

)( :equation Debye

js

1

)( :equation Debye

Measurement Techniques

Parallel Plate

ResonantCavity

TransmissionLine including

Free Space

CoaxialProbe

Which Technique is Best?

It Depends…

Frequency of interest

Expected value of er

Required measurement accuracy

Which Technique is Best?

It Depends… on

Frequency of interest

Expected value of er

Required measurement accuracy

Material properties (i.e., homogeneous, isotropic)

Form of material (i.e., liquid, powder, solid, sheet)

Sample size restrictions

Which Technique is Best?

It Depends… on

Frequency of interest

Expected value of er

Required measurement accuracy

Material properties (i.e., homogeneous, isotropic)

Form of material (i.e., liquid, powder, solid, sheet)

Sample size restrictions

Destructive or non-destructive

Contacting or non-contacting

Temperature

Which Technique is Best?

It Depends… on

Measurement Techniques vs. Frequency and Material Loss

Parallel Plate

Frequency

Loss

Transmission line

Resonant Cavity

Coaxial Probe

MicrowaveRF Millimeter-waveLow frequency

High

Medium

Low

Free Space

50 MHz 20 GHz 40 GHz 60 GHz5 GHz 500+ GHz

Measurement Techniques vs. Frequency and Material Loss

Frequency

Loss

Coaxial Probe

MicrowaveRF Millimeter-waveLow frequency

High

Medium

Low

50 MHz 20 GHz 40 GHz 60 GHz5 GHz 500+ GHz

Measurement Techniques vs. Frequency and Material Loss

Frequency

Loss

Coaxial Probe

MicrowaveRF Millimeter-waveLow frequency

High

Medium

Low

50 MHz 20 GHz 40 GHz 60 GHz5 GHz 500+ GHz

Measurement Techniques vs. Frequency and Material Loss

Frequency

Loss

Transmission line

Coaxial Probe

MicrowaveRF Millimeter-waveLow frequency

High

Medium

Low

Free Space

50 MHz 20 GHz 40 GHz 60 GHz5 GHz 500+ GHz

Measurement Techniques vs. Frequency and Material Loss

Frequency

Loss

Transmission line

Coaxial Probe

MicrowaveRF Millimeter-waveLow frequency

High

Medium

Low

Free Space

50 MHz 20 GHz 40 GHz 60 GHz5 GHz 500+ GHz

Measurement Techniques vs. Frequency and Material Loss

Parallel Plate

Frequency

Loss

Transmission line

Coaxial Probe

MicrowaveRF Millimeter-waveLow frequency

High

Medium

Low

Free Space

50 MHz 20 GHz 40 GHz 60 GHz5 GHz 500+ GHz

Measurement Techniques vs. Frequency and Material Loss

Parallel Plate

Frequency

Loss

Transmission line

Resonant Cavity

Coaxial Probe

MicrowaveRF Millimeter-waveLow frequency

High

Medium

Low

Free Space

50 MHz 20 GHz 40 GHz 60 GHz5 GHz 500+ GHz

Parallel Plate Capacitor System

tA

Cr

0

'

tA

Cr

0

'

LCR or Impedance Analyzer

Dielectric Test Fixture

(magnetic fixture also available)

Dtan Dtan

tA

Impedance Analyzers and Fixtures

Measurement Techniques that use a Vector Network Analyzer

•Coaxial Probe

•Transmission Line and Free-space

•Resonant Cavity

Coaxial Probe System

Network Analyzer (or E4991A Impedance

Analyzer)

85070EDielectric

Probe

GP-IB or LAN

Computer (not required for

PNA)

85070E Software (included in kit)

Material assumptions:

• effectively infinite thickness

• non-magnetic

• isotropic

• homogeneous

• no air gaps or bubbles

Material assumptions:

• effectively infinite thickness

• non-magnetic

• isotropic

• homogeneous

• no air gaps or bubbles

Coaxial Probe

11

Reflection

(S )

Three Probe Designs

High Temperature Probe

•0.200 – 20GHz (low end 0.01GHz with impedance analyzer)•Withstands -40 to 200 degrees C •Survives corrosive chemicals•Flanged design allows measuring flat surfaced solids.

Three Probe Designs

Slim Form Probe

•0.500 – 50GHz•Low cost consumable design•Fits in tight spaces, smaller sample sizes •For liquids and soft semi-solids only

Three Probe Designs

Performance Probe

Combines rugged high temperature performance with high frequency performance, all in one slim design.

•0.500 – 50GHz•Withstands -40 to 200 degrees C•Hermetically sealed on both ends, OK for autoclave•Food grade stainless steel

Transmission Line System

Network Analyzer

GPIB or LAN

Sample holder connected between coax

cables

Computer (not required for

PNA)

85071E Materials Measurement

Software

Transmission Line

l

Reflection(S )11

Transmission(S )21

Material assumptions:

• sample fills fixture cross section

• no air gaps at fixture walls

• flat faces, perpendicular to long axis

• Known thickness > 20/360 λ

Material assumptions:

• sample fills fixture cross section

• no air gaps at fixture walls

• flat faces, perpendicular to long axis

• Known thickness > 20/360 λ

Transmission Line Sample Holders

Waveguide

Coaxial

Transmission Algorithms

(85071E also has three reflection algorithms)

Algorithm Measured S-parameters

Optimum Length Output

Nicolson-Ross S11,S21,S12,S22 /4r and r

Precision (NIST) S11,S21,S12,S22 n r

Fast S21,S12 n r

Computer (not required for

PNA)

85071E Materials Measurement

Software

Transmission Free-Space System

GP-IB or LAN

Network Analyzer

Sample holder fixtured between two antennae

Transmission Free-Space

Material assumptions:

• Flat parallel faced samples

• Sample in non-reactive region

• Beam spot is contained in sample

• Known thickness > 20/360 λ

Material assumptions:

• Flat parallel faced samples

• Sample in non-reactive region

• Beam spot is contained in sample

• Known thickness > 20/360 λ

l

Reflection

(S11 )

Transmission

(S21 )

Non-Contacting method for High or Low Temperature Tests.

Free Space with Furnace

75-110GHz Free Space System

Free Space 75-110GHz Quasi-Optical System

Agilent Technical

Forum

Free Space Materials

Characterization

15 October 2008

Page 40

Free Space 75-110GHz Quasi-Optical System

Free Space 75-110GHz Quasi-Optical System

Free Space 75-110GHz Quasi-Optical System

Free Space 75-110GHz Quasi-Optical System

Reflectivity Measurement System

GP-IB or LAN

Network Analyzer with Time Domain

option

NRL Arch Fixture with MUT

Computer (not required

for PNA)

85071E Materials

Measurement Software

with Reflectivity Option 200

NRL Arch

Incident Wave

Reflected

Wave

port 1 port 2

MUT

S21

Results in dB

Resonant Cavity System

Resonant Cavity with sample

connected between ports.

Network Analyzer

GP-IB or LAN

Computer (not required for

PNA)

Resonant Cavity Software

Resonant Cavity Technique

Q

fs ffc

sQc

empty cavity

sample insertedfc = Resonant Frequency of Empty Cavity

fs = Resonant Frequency of Filled Cavity

Qc = Q of Empty Cavity

Qs = Q of Filled Cavity

Vs = Volume of Empty Cavity

Vc = Volume of Sample

ASTM 2520

Resonant Cavity Fixtures

Agilent Split Cylinder Resonator IPC TM-650-

2.5.5.5.13

Split Post Dielectric Resonators from

QWED

ASTM 2520 Waveguide Resonators

Resonant vs. Broadband Transmission Techniques

Resonant Broadband

Low Loss materialsYes

er” resolution ≤10-4

No

er” resolution ≥10-2-10-3

Thin Films and SheetsYes

10GHz sample thickness <1mm

No

10GHz optimum thickness ~ 5-10mm

Calibration Required No Yes

Measurement Frequency Coverage Single Frequency Broadband or Banded

Summary Technique and Strengths

Parallel Plate Low Frequency

Best for thin flat sheets

Coaxial Probe Broadband

Best for liquids, semi-solids

Transmission Line Broadband

Best for machine-able solids

Transmission Free Space

Broadband, mm-wave

Non-contacting

Resonant Cavity Single frequency

High accuracy, Best for low loss, or very thin samples

Microwave Dielectric Measurement Solutions

Model Number

Description

85070

E020

030

050

Dielectric Probe Kit High Temperature Probe

Slim Form Probe

Performance Probe

85071

E100

200

300

E01

E03

E04

Materials Measurement Software Free Space Calibration

Reflectivity Software

Resonant Cavity Software

75-110GHz Free Space Fixture

2.5GHz Split Post Dielectric Resonator

5GHz Split Post Dielectric Resonator

85072

A

10GHz Split Cylinder Resonant Cavity

For More Information

Visit our website at:

www.agilent.com/find/materials

For Product Overviews, Application Notes, Manuals, Quick Quotes,

international contact information…

For More Information

Visit our website at:

www.agilent.com/find/materials

Call our on-line technical support:

+1 800 829-4444

For Product Overviews, Application Notes, Manuals, Quick Quotes,

international contact information…

For personal help for your application, formal quotes, to get in touch with Agilent field engineers in your area.

ReferencesR N Clarke (Ed.), “A Guide to the Characterisation of DielectricMaterials at RF and Microwave Frequencies,” Published by The Institute of Measurement & Control (UK) & NPL, 2003

J. Baker-Jarvis, M.D. Janezic, R.F. Riddle, R.T. Johnk, P. Kabos, C. Holloway, R.G. Geyer, C.A. Grosvenor, “Measuring the Permittivity and Permeability of Lossy Materials: Solids, Liquids, Metals, Building Materials, and Negative-Index Materials,” NIST Technical Note 15362005

“Test methods for complex permittivity (Dielectric Constant) of solid electrical insulating materials at microwave frequencies and temperatures to 1650°, ” ASTM Standard D2520, American Society for Testing and Materials

Janezic M. and Baker-Jarvis J., “Full-wave Analysis of a Split-Cylinder Resonator for Nondestructive Permittivity Measurements,” IEEE Transactions on Microwave Theory and Techniques vol. 47, no. 10, Oct 1999, pg. 2014-2020

J. Krupka , A.P. Gregory, O.C. Rochard, R.N. Clarke, B. Riddle, J. Baker-Jarvis, “Uncertainty of Complex Permittivity Measurement by Split-Post Dielectric Resonator Techniques,” Journal of the European Ceramic SocietyNo. 10, 2001, pg. 2673-2676

“Basics of Measureing the Dielectric Properties of Materials”. Agilent application note. 5989-2589EN, April 28, 2005