Shelley Begley Application Development Engineer Agilent Technologies Electromagnetic Properties of Materials: Characterization at Microwave Frequencies.
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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
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