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

Definitions Measurement Techniques Coaxial Probe Transmission Line Free-Space Resonant Cavity Summary Agenda

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

Permittivity and Permeability Definitions interaction of a material in the presence of an external electric field. Permittivity (Dielectric Constant)

Permittivity and Permeability Definitions interaction of a material in the presence of an external electric field. Permittivity (Dielectric Constant)

Permittivity and Permeability Definitions interaction of a material in the presence of an external electric field. interaction of a material in the presence of an external magnetic field. Permittivity (Dielectric Constant) Permeability

Permittivity and Permeability Definitions interaction of a material in the presence of an external electric field. interaction of a material in the presence of an external magnetic field. Permittivity (Dielectric Constant) Permeability

Electromagnetic Field Interaction Electric Magnetic Permittivity Permeability Fields STORAGE MUT STORAGE

Electromagnetic Field Interaction Electric Magnetic Permittivity Permeability Fields STORAGE LOSS MUT STORAGE LOSS

Loss Tangent Dissipation Factor Quality Factor

Relaxation Constant   = Time required for 1/e of an aligned system to return to equilibrium or random state, in seconds Water at 20 o C f, GHz most energy is lost at 1/ 

Techniques Transmission LIne Resonant Cavity Free Space Coaxial Probe

Which Technique is Best? It Depends…

Frequency of interest Expected value of e r and m r Required measurement accuracy Which Technique is Best? It Depends… on

Frequency of interest Expected value of e r and m r 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 e r and m r 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 Microwave RF Millimeter-wave Low frequency High Medium Low Free Space 50 MHz20 GHz 40 GHz 60 GHz 5 GHz 500+ GHz

Measurement Techniques vs. Frequency and Material Loss Frequency Loss Coaxial Probe Microwave RF Millimeter-wave Low frequency High Medium Low 50 MHz20 GHz 40 GHz 60 GHz 5 GHz 500+ GHz

Measurement Techniques vs. Frequency and Material Loss Frequency Loss Coaxial Probe Microwave RF Millimeter-wave Low frequency High Medium Low 50 MHz20 GHz 40 GHz 60 GHz 5 GHz 500+ GHz

Measurement Techniques vs. Frequency and Material Loss Frequency Loss Transmission line Coaxial Probe Microwave RF Millimeter-wave Low frequency High Medium Low Free Space 50 MHz20 GHz 40 GHz 60 GHz 5 GHz 500+ GHz

Measurement Techniques vs. Frequency and Material Loss Frequency Loss Transmission line Coaxial Probe Microwave RF Millimeter-wave Low frequency High Medium Low Free Space 50 MHz20 GHz 40 GHz 60 GHz 5 GHz 500+ GHz

Measurement Techniques vs. Frequency and Material Loss Frequency Loss Transmission line Resonant Cavity Coaxial Probe Microwave RF Millimeter-wave Low frequency High Medium Low Free Space 50 MHz20 GHz 40 GHz 60 GHz 5 GHz 500+ GHz

Coaxial Probe System Network Analyzer (or E4991A Impedance Analyzer) 85070E Dielectric 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 1 Reflection (S ) rr

Three Probe Designs High Temperature Probe – 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 – 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 – 50GHz Withstands -40 to 200 degrees C Hermetically sealed on both ends, OK for autoclave Food grade stainless steel

Coaxial Probe Example Data

Martini Meter! 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 Split Post Dielectric Resonators from QWED ASTM 2520 Waveguide Resonators

Resonant Cavity Technique f f c Q c empty cavity fc = 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 f s f f c s Q c empty cavity sample inserted fc = 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 f s f f c s Q c empty cavity sample inserted fc = 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 f s f f c s Q c empty cavity sample inserted fc = 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 ResonantBroadband Low Loss materials Yes e r ” resolution ≤10 -4 No e r ” resolution ≥ Thin Films and Sheets Yes 10GHz sample thickness <1mm No 10GHz optimum thickness ~ 5-10mm Calibration RequiredNoYes Measurement Frequency Coverage Single FrequencyBroadband 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 NumberDescription 85070E Dielectric Probe Kit High Temperature Probe Slim Form Probe Performance Probe 85071E E01 E03 E04 Materials Measurement Software Free Space Calibration Reflectivity Software Resonant Cavity Software GHz Free Space Fixture 2.5GHz Split Post Dielectric Resonator 5GHz Split Post Dielectric Resonator 85072A10GHz Split Cylinder Resonant Cavity

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

Transmission Algorithms ( 85071E also has three reflection algorithms) AlgorithmMeasured S-parametersOutput Nicolson-RossS11,S21,S12,S22  r and  r Precision (NIST)S11,S21,S12,S22 rr FastS21,S12 rr