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Free Space Materials Characterization
Shelley Blasdel Begley Application Development Engineer
Agilent Technologies
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 1
Agenda
What is it?Free Space Measurement SystemsCalibrationMeasurement Results
Agilent Technologies
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 2
What is Free Space Materials Characterization?
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 3
Measuring Electromagnetic Properties of Materials Using Free Space Measurement Technique.
Important for:Circuit designMilitary ApplicationsCar Radar ApplicationsNew Materials ResearchIncoming Inspection Quality AssuranceHealth and Safetyand more…
Electromagnetic Materials
Radar Absorbing and Stealth Materials
Radome Materials
Electronic Substrate and Packaging Materials
Specific Absorption Rate (SAR) Phantoms
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 4
Transmission Free-Space System
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 5
GP-IB or LAN
Network Analyzer
Sample holder fixtured between two antennae
Computer (not required for
PNA)
85071E Materials Measurement Software
With Option 100 Free Space Calibration
Bio-dielectrics: Theories, Mechanisms, Applications, Stamford Hall, Leicester,
UK
Lightwave Analogy
Incident
Lens
Bio-dielectrics: Theories, Mechanisms, Applications, Stamford Hall, Leicester,
UK
Lightwave Analogy
Incident
Reflected
Lens
Bio-dielectrics: Theories, Mechanisms, Applications, Stamford Hall, Leicester,
UK
Lightwave Analogy
Incident
Reflected
Lens
Bio-dielectrics: Theories, Mechanisms, Applications, Stamford Hall, Leicester,
UK
Lightwave Analogy
Incident
Reflected
Transmitted
Lens
Agilent Technical ForumFree Space Materials Characterization
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Network Analyzer Block Diagram
SOURCE
Incident
Reflected
Transmitted
MUT
Fixture
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 11
Network Analyzer Block Diagram
SIGNALSEPARATION
SOURCE
Incident
Reflected
Transmitted
MUT
Fixture
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 12
Network Analyzer Block Diagram
RECEIVER / DETECTOR
REFLECTED(A)
INCIDENT (R)
SIGNALSEPARATION
SOURCE
Incident
Reflected
Transmitted
MUT
Fixture
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 13
Network Analyzer Block Diagram
RECEIVER / DETECTOR
REFLECTED(A)
TRANSMITTED(B)
INCIDENT (R)
SIGNALSEPARATION
SOURCE
Incident
Reflected
Transmitted
MUT
Fixture
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 14
Network Analyzer Block Diagram
RECEIVER / DETECTOR
PROCESSOR / DISPLAY
REFLECTED(A)
TRANSMITTED(B)
INCIDENT (R)
SIGNALSEPARATION
SOURCE
Incident
Reflected
Transmitted
MUT
Fixture
= S11Incident
Reflected Transmitted
Incident
= S21
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
Before a Measurement Can be Made…
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 16
Calibration is required!
Agilent Technical ForumFree Space Materials Characterization
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Thru
Reflect
Match
TRM Calibration
Hard to get broadband absorbers for matchHard to get broadband absorbers for match
Agilent Technical ForumFree Space Materials Characterization
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TRL Calibration
Thru
Reflect
Line
Move the antenna away to compensate for the thickness of the short. Move it back for the next step.
Move the antenna away on a quarter-wavelength and then back in the original position.
Precise positioning fixtures are expensivePrecise positioning fixtures are expensive
Gated Reflect Line (GRL) CalibrationTwo Tiered Process
Two port calibration at waveguide or coax input into antennas removes errors associated with network analyzer and cables.
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 19
ECal, SOLT or TRL Cal done here
Gated Reflect Line (GRL) CalibrationTwo Tiered Process
Two additional free space calibration standards remove errors from antennas and fixture.
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 20
Reflect
(metal plate of
known thickness)
Line
(empty fixture)
GRL Cal – How it works
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 21
GRL Cal Error Model (forward only)
•Coax or Waveguide 2-port Cal corrects errors from end of cable back into the instrument.
2-port Cal Terms 2-port Cal Terms
D
MUT
Ms
Tr
Tt
Ml
1
S11 S22
S21
S12
GRL Error Adapter
GRL Error Adapter
GRL Cal – How it works
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 22
GRL Cal Error Model (forward only)
•Coax or Waveguide 2-port Cal corrects errors from end of cable back into the instrument.
2-port Cal Terms 2-port Cal Terms
D
MUT
Ms
Tr
Tt
Ml
1
S11 S22
S21
S12
GRL Error Adapter
GRL Error Adapter
GRL Cal – How it works
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 23
GRL Cal Error Model (forward only)
•Coax or Waveguide 2-port Cal corrects errors from end of cable back into the instrument.
2-port Cal Terms 2-port Cal Terms
D
MUT
Ms
Tr
Tt
Ml
1
S11 S22
S21
S12
GRL Error Adapter
GRL Error Adapter
GRL Cal – How it works
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 24
GRL Cal Error Model (forward only)
•Coax or Waveguide 2-port Cal corrects errors from end of cable back into the instrument.
•Errors from Antennas and Fixture can be thought of as being lumped into a GRL error adapter.
•The GRL error adapter is quantified by measurements of reflect and line standards.
2-port Cal Terms 2-port Cal Terms
D
MUT
Ms
Tr
Tt
Ml
1
S11 S22
S21
S12
GRL Error Adapter
GRL Error Adapter
GRL Cal – How it works
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 25
Time Domain of Empty Free Space Fixture
Transmitting Antenna
Air
Receiving Antenna
gate
GRL Cal – How it works
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 26
GRL Cal Error Model (forward only)
•Coax or Waveguide 2-port Cal corrects errors from end of cable back into the instrument.
•Errors from Antennas and Fixture can be thought of as being lumped into a GRL error adapter.
•The GRL error adapter is quantified by measurements of reflect and line standards.
•The original 2-port Cal is modified to correct for the error adapter.
2-port Cal Terms 2-port Cal Terms
D
MUT
Ms
Tr
Tt
Ml
1
S11 S22
S21
S12
GRL Error Adapter
GRL Error Adapter
GRL Cal – How it works
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 27
GRL Cal Error Model (forward only)
•Coax or Waveguide 2-port Cal corrects errors from end of cable back into the instrument.
•Errors from Antennas and Fixture can be thought of as being lumped into a GRL error adapter.
•The GRL error adapter is quantified by measurements of reflect and line standards.
•The original 2-port Cal is modified to correct for the error adapter.
2-port Cal Terms 2-port Cal Terms
D
MUT
Ms
Tr
Tt
Ml
1
S11 S22
S21
S12
GRL Error Adapter
GRL Error Adapter
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 28
Free-space X-Band System
Free Space 40 – 60GHz System
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 29
Bio-dielectrics: Theories, Mechanisms, Applications, Stamford Hall, Leicester, UK
A Simple Free Space Powder Fixture
Powder in Tray Placed Between Antennae
Close Up
Free Space 75 – 110GHz Standard Gain Horn System
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 31
Free Space W-band System
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Free Space 75-110GHz Quasi-Optical System
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 33
Free Space 75-110GHz Quasi-Optical System
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 34
Free Space 75-110GHz Quasi-Optical System
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 35
Free Space 75-110GHz Quasi-Optical System
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 36
Free Space 75-110GHz Quasi-Optical System
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 37
Free Space 75-110GHz Quasi-Optical System
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 38
Measurement Results
Real part of EpsilonRexolite measured with 110Ghz PNA and GRL Cal
y = -3E-14x + 2.5265
2.47
2.48
2.49
2.5
2.51
2.52
2.53
2.54
2.55
2.56
2.57
7.500E+10 8.000E+10 8.500E+10 9.000E+10 9.500E+10 1.000E+11 1.050E+11 1.100E+11
frequency (hz)
e'
Std Gain Horn QO table Linear (QO table)
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 39
Measurement Results
Imaginary part of EpsilonRexolite measured with 110Ghz PNA and GRL Cal
y = -2E-14x + 0.003
-0.02
-0.015
-0.01
-0.005
0
0.005
0.01
0.015
0.02
0.025
0.03
7.500E+10 8.000E+10 8.500E+10 9.000E+10 9.500E+10 1.000E+11 1.050E+11 1.100E+11
frequency (hz)
e"
Std Gain Horn QO table Linear (QO table)
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 40
Conclusion
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 41
Free Space is a useful method for measuring electromagnetic properties of a of materials.
Innovative calibration overcomes challenges of previous free space error correction methods.
For More Information
Visit our website at: www.agilent.com/find/materials
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 42
References
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 43
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 SocietyNo. 10, 2001, pg. 2673-2676
“Basics of Measureing the Dielectric Properties of Materials”. Agilent application note. 5989-2589EN, April 28, 2005
mm-Wave Free Space Results
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 44
Rexolite expected
value
e’ = 2.53
Apendix
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 45
• • • •Section Title
GRL Cal – System Considerations
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 46
•Determine Sample Position
•Determine Sample Size
•Choose Metal Plate
Fixture with Metal Plate
Metal Plate
GRL Cal - Considerations
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 47
Transmitting Antenna
20nS
Receiving Antenna
• Choose Number of points to Avoid Aliasing
Empty Fixture
Minumum Number of Points =
1 + Range * (Stop Frequency – Start Frequency)
Where Range is the needed alias free range in Seconds
GRL Cal - Considerations
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 48
• Choose Time Domain Parameters
Empty Fixture Fixture with Metal Plate
Metal Plate at 3.5nS
Air at 3.5nS
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 49
Quasi Optical System Schematic
Additional information available at : http://www.terahertz.co.uk/TKI/Agilent/Agilent_VNA_QO.html
MUT and GRL Error Adapters
After 2-Port Calibration
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 50
MUT
S11 S22
S21
S12
T22 T11
T12
T21
O11 O22
O21
O12
Six Unknowns
021 = O12
O11
O22
T21 = T12
T11
T22
MUT and GRL Error Adapters
After O11 and T11 are embedded into the original 2-Port calibration.
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 51
MUT
S11 S22
S21
S12
T22
T12
T21
O22
O21
O12
Four Unknowns
O21 = O12
O22
T21 = T12
T22
GRL Metal Plate Standard
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 52
P11 = P22 = -1
P21=P12=0.
21 12plate_1
22
O O
1 O
21 12plate_2
22
T T
1 T
MUT
S11 S22
S21
S12
T22
T12
T21
O22
O21
O12
GRL Thru Standard (Air)
Agilent Technical ForumFree Space Materials Characterization
15 October 2008Page 53
A11=A22=0
A21 = A12 =
= frequency= permittivity of air= permeability of air.d= thickness of the metal plate
21 12 21 12 22air_1
22 22
A A O O T
1 O T
21 12 21 12 22air_2
22 22
A A T T O
1 T O
j ude
MUT
S11 S22
S21
S12
T22
T12
T21
O22
O21
O12