Electromagnetic Properties of Materials:
Characterization at Microwave Frequencies and Beyond
Shelley Begley
Application Development Engineer
Agilent Technologies
Agenda
Definitions
Measurement Techniques
Parallel Plate
Coaxial Probe
Transmission Line and Free-Space
Resonant Cavity
Summary
Definitions
Permittivity 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
'
r
"
r
Df
Dk
Permittivity and Permeability Definitions
Permittivity
(Dielectric Constant)

'
"
   r   r  j r
0
interaction of a material in the
presence of an external electric field.
Permittivity and Permeability Definitions
Permittivity
(Dielectric Constant)

'
"
   r   r  j r
0
interaction of a material in the
presence of an external electric field.
Dk
Permittivity and Permeability Definitions
Permittivity
(Dielectric Constant)
Permeability


'
"
'
"
  r  j r
   r   r  j r  
0
0
interaction of a material in the
presence of an external electric field.
Dk
interaction of a material in the
presence of an external magnetic field.
Permittivity and Permeability Definitions
Permittivity
(Dielectric Constant)
Permeability


'
"
'
"
  r  j r
   r   r  j r  
0
0
interaction of a material in the
presence of an external electric field.
Dk
interaction of a material in the
presence of an external magnetic field.
Electromagnetic Field Interaction
STORAGE
Electric
Fields
Permittivity
'
r  r

MUT
Magnetic
Fields
Permeability
r 
"
j r
STORAGE
'
r

"
jr
Electromagnetic Field Interaction
STORAGE
Electric
Fields
LOSS
Permittivity
'
r  r
Magnetic
Fields

MUT
Permeability
r 
"
j r
STORAGE
LOSS
'
r

"
jr
Loss Tangent
r
tan   '
r
"

''
r
r

'
r
1
Energy Lost per Cycle
tan   D  
Q Energy Stored per Cycle
D
Df
Dissipation Factor Q
Quality Factor
Relaxation Constant t
Water at 20o C
t = Time required for 1/e of
an aligned system to return
to equilibrium or random
state, in seconds.
100
 r'
10
1
1
t

 c 2f c
"
r
most energy is lost at 1/t
1
1
Debye equation :  ( )    
s  
1  jt
10
100
f,
GHz
Measurement Techniques
Parallel
Plate
Transmission
Line including
Free Space
Coaxial
Probe
Resonant
Cavity
Which Technique is Best?
It Depends…
Which Technique is Best?
It Depends… on
 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
Measurement Techniques
vs. Frequency and Material Loss
Loss
High
Coaxial Probe
Transmission line
Medium
Free Space
Parallel
Plate
Resonant Cavity
Low
Frequency
50 MHz
Low frequency
5 GHz
RF
20 GHz
Microwave
40 GHz
60 GHz
500+ GHz
Millimeter-wave
Measurement Techniques
vs. Frequency and Material Loss
Loss
High
Coaxial Probe
Medium
Low
Frequency
50 MHz
Low frequency
5 GHz
RF
20 GHz
Microwave
40 GHz
60 GHz
500+ GHz
Millimeter-wave
Measurement Techniques
vs. Frequency and Material Loss
Loss
High
Coaxial Probe
Medium
Low
Frequency
50 MHz
Low frequency
5 GHz
RF
20 GHz
Microwave
40 GHz
60 GHz
500+ GHz
Millimeter-wave
Measurement Techniques
vs. Frequency and Material Loss
Loss
High
Coaxial Probe
Transmission line
Medium
Free Space
Low
Frequency
50 MHz
Low frequency
5 GHz
RF
20 GHz
Microwave
40 GHz
60 GHz
500+ GHz
Millimeter-wave
Measurement Techniques
vs. Frequency and Material Loss
Loss
High
Coaxial Probe
Transmission line
Medium
Free Space
Low
Frequency
50 MHz
Low frequency
5 GHz
RF
20 GHz
Microwave
40 GHz
60 GHz
500+ GHz
Millimeter-wave
Measurement Techniques
vs. Frequency and Material Loss
Loss
High
Coaxial Probe
Transmission line
Medium
Free Space
Parallel
Plate
Low
Frequency
50 MHz
Low frequency
5 GHz
RF
20 GHz
Microwave
40 GHz
60 GHz
500+ GHz
Millimeter-wave
Measurement Techniques
vs. Frequency and Material Loss
Loss
High
Coaxial Probe
Transmission line
Medium
Free Space
Parallel
Plate
Resonant Cavity
Low
Frequency
50 MHz
Low frequency
5 GHz
RF
20 GHz
Microwave
40 GHz
60 GHz
500+ GHz
Millimeter-wave
Parallel Plate Capacitor System
'
r
LCR or Impedance
Analyzer
C

A
0
t
tan   D
A
Dielectric Test
Fixture
t
(magnetic fixture
also available)
Impedance Analyzers and Fixtures
Measurement Techniques that use a
Vector Network Analyzer
•Coaxial Probe
•Transmission Line and Free-space
•Resonant Cavity
Coaxial Probe System
Computer
(not required for
PNA)
Network Analyzer
(or E4991A Impedance
Analyzer)
GP-IB or
LAN
85070E Software
(included in kit)
85070E
Dielectric
Probe
Coaxial Probe
Material assumptions:
• effectively infinite thickness
• non-magnetic
• isotropic
Reflection
1
(S1 )
• homogeneous
• no air gaps or bubbles
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
Computer
(not required for
PNA)
Network Analyzer
GPIB or
LAN
85071E Materials
Measurement
Software
Sample holder
connected between coax cables
Transmission Line
Material assumptions:
• sample fills fixture cross section
• no air gaps at fixture walls
• flat faces, perpendicular to long axis
l
• Known thickness > 20/360 λ
Reflection
(S11)
Transmission
(S21 )
Transmission Line Sample Holders
Coaxial
Waveguide
Transmission Algorithms
Algorithm
Measured S-parameters
Optimum
Length
Nicolson-Ross
S11,S21,S12,S22
l/4
r and r
Precision (NIST)
S11,S21,S12,S22
n l/2
r
Fast
S21,S12
n l/2
r
(85071E also has three reflection algorithms)
Output
Transmission Free-Space System
Computer
(not required for
PNA)
Network Analyzer
GP-IB or LAN
85071E Materials
Measurement
Software
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
l
• Known thickness > 20/360 λ
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
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
Network Analyzer
with Time Domain
option
Computer
(not required for
PNA)
GP-IB or
LAN
85071E Materials
Measurement
Software
with Reflectivity
Option 200
NRL Arch Fixture with MUT
NRL Arch
Results in dB
port 1
port 2
S21
Incident
Wave
Reflected
Wave
MUT
Resonant Cavity System
Computer
(not required for
PNA)
Network Analyzer
GP-IB or LAN
Resonant Cavity
Software
Resonant Cavity with sample
connected between ports.
Resonant Cavity Technique
empty cavity
fc = Resonant Frequency of Empty Cavity
fs = Resonant Frequency of Filled Cavity
sample inserted
Qc
Qs
Qc = Q of Empty Cavity
Qs = Q of Filled Cavity
Vs = Volume of Empty Cavity
Vc = Volume of Sample
fs
fc
f
Vc  f c  f s 
 r  1 
 2.303
2Vs f s
Vc  1
1 
    0.003
 r 
4Vs  Qs Qc 
ASTM 2520
Resonant Cavity Fixtures
Agilent Split Cylinder
Resonator IPC TM-6502.5.5.5.13
ASTM 2520 Waveguide
Resonators
Split Post Dielectric
Resonators from QWED
Resonant vs. Broadband Transmission
Techniques
Resonant
Broadband
Yes
No
er” resolution ≤10-4
er” resolution ≥10-2-10-3
Yes
No
Thin Films and Sheets
10GHz sample thickness
<1mm
10GHz optimum thickness ~
5-10mm
Calibration Required
No
Yes
Measurement Frequency
Coverage
Single Frequency
Broadband or Banded
Low Loss materials
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
Resonant Cavity
Single frequency
Non-contacting
High accuracy, Best for low
loss, or very thin samples
Microwave Dielectric Measurement
Solutions
Model Number
Description
85070E
Dielectric Probe Kit
020
030
050
85071E
Slim Form Probe
Performance Probe
Materials Measurement Software
100
200
300
E01
E03
E04
85072A
High Temperature Probe
Free Space Calibration
Reflectivity Software
Resonant Cavity Software
75-110GHz Free Space Fixture
2.5GHz Split Post Dielectric Resonator
5GHz Split Post Dielectric Resonator
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
For Product Overviews, Application Notes,
Manuals, Quick Quotes, international contact
information…
Call our on-line technical support:
+1 800 829-4444
For personal help for your application, formal
quotes, to get in touch with Agilent field
engineers in your area.
References
R 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 Society
No. 10, 2001, pg. 2673-2676
“Basics of Measureing the Dielectric Properties of Materials”. Agilent application note. 5989-2589EN, April 28, 2005