Shelley BegleyApplication Development EngineerAgilent Technologies

Electromagnetic Properties of Materials: Characterization at Microwave Frequencies and Beyond

Definitions

Measurement TechniquesCoaxial Probe

Transmission LineFree-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

Techniques

Transmission LIne

ResonantCavity

Free Space

CoaxialProbe

Which Technique is Best?

It Depends…

Frequency of interest

Expected value of er and mr

Required measurement accuracy

Which Technique is Best?

It Depends… on

Frequency of interest

Expected value of er and mr

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 and mr

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

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

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

Coaxial Probe System

Network Analyzer (or E4991A Impedance

Analyzer)

85070EDielectric

Probe

GP-IB or LAN

85070E Software (included in kit)

Calibration is required

Computer (Optional for PNA or ENA-

C)

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 )

r

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

Coaxial Probe Example Data

Coaxial Probe Example Data

Martini Meter!

80 85 90 95 100

Measured Y

80

85

90

95

100

Pre

d C

al

100 real

96.6 real

80.0 real

98.0 real

90.9 real

99.5 real

96.2 real

97.6 real

87.0 real

99.0 real

95.7 real

97.1 real

83.3 real

98.5 real

95.2 real

5

Infometrix, Inc.

Transmission Line System

Network Analyzer

GPIB or LAN

Sample holder connected between coax

cables

85071E Materials Measurement

Software

Calibration is required

Computer (Optional for PNA or ENA-

C)

Transmission Line Sample Holders

Waveguide

Coaxial

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

r and r

85071E Materials Measurement

Software

Transmission Free-Space System

GP-IB or LAN

Network Analyzer

Sample holder fixtured between two antennae

Calibration is required

Computer (Optional for PNA or ENA-

C)

Non-Contacting method for High or Low Temperature Tests.

Free Space with Furnace

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 )

r and r

Transmission Example Data

Resonant Cavity System

Resonant Cavity with sample

connected between ports.

Network Analyzer

GP-IB or LAN

Computer (Optional for PNA or ENA-

C)

Resonant Cavity Software

No calibration required

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 Cavity Technique

ffc

Qc

empty cavityfc = 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

S21

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

S21

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

S21

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

S21

Resonant Cavity Example Data

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

Coaxial Probe Broadband r

Best for liquids, semi-solids

Transmission Line Broadband r & r

Best for solids or powders

Transmission Free Space

Broadband, mm-wave r

& r

Non-contacting

Resonant Cavity Single frequency r

High accuracy, Best for low loss, or 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

Transmission Algorithms

(85071E also has three reflection algorithms)

Algorithm Measured S-parameters Output

Nicolson-Ross S11,S21,S12,S22r and r

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

Fast S21,S12 r