Material Measurement Basics

Transcription

1 Material Measurement Basics Agenda Fundamentals LCR meters and Impedance Analyzers RF and MW Network Analyzer Transmission Measurements Dielectric Probe Measurements Cavity Resonator Measurements

2 Objectives Provide basic education on dielectric measurements Provide guidance in choosing the best measurement technique for a given application Give practical information for improving measurements Why make measurements? Development of new materials Controlling a manufacturing process Incoming inspection of materials Shorter design cycles Higher performance Reduced scrap

3 Parallel Plate Capacitor (DC) A V C = C - - t κ C = 0 A t Capacitance with no dielectric (vacuum) κ = ε r = C C Dielectric constant or permittivity (real) 0 Parallel Plate Capacitor (AC) V I t A C G - I = I + I = V ( jωc0κ G) c l + if G = ωc 0 κ" then I = V jω C )( κ jκ") = V ( jω ) κ ( 0 C0

4 D = ε E Permittivity (electromagnetic fields) Definition of electric displacement (electric flux density) ε = ε* = ε0ε r ε ε r Absolute permittivity or permittivity Relative permittivity or dielectric constant ε x 10 F / m 36π Free space permittivity κ = ε ε 0 = ε r r Permittivity is complex = ε jε " r The permittivity is often called dielectric constant, but is changing with frequency. storage loss ε r " ε r Permittivity Measure of how much energy from an external electric field is stored in the material Loss factor Measure of how much dissipative or lossy a material is to an external field

5 ε r ε r ε r Loss Tangent ε κ" tanδ = r = ε κ " r 1 tanδ = D = = Q Energy Lost per Cycle Energy Stored per Cycle D Dissipation Factor Q Quality Factor Core material R Inductor L = L 0 µ L µ = L L 0 Real permeability L 0 Inductance of coil in free space

6 Permeability is complex µ " µ = = µ r jµ r µ 0 storage loss 0 7 µ = 4πx 10 H / m Free space permeability µ = µ * = µ 0µ r µ µ r Absolute permeability Relative permeability Electromagnetic Field Interaction Electric Fields Permittivity r r " r ε = ε jε Dielectric Constant STORAGE LOSS MUT STORAGE LOSS Magnetic Fields Permeability r " r µ r = µ jµ

7 Dielectric Properties (at 3 GHz) TiO 2 Low Loss Lossy Water Salt Water ε r Air Steak Alumina Alcohol PC Board Quartz Wood 20% Mylar Ice 10% Teflon 0% " / tanδ = ε r ε r Dielectric Mechanisms vs. Frequency + ε r Dipolar Ionic - Atomic - Electronic ε r f MW IR V UV

8 Relaxation Time τ 100 ε s Water at 20 o C (f c = 22 GHz) Time required for 1/e of a perturbed (aligned) system to return to equilibrium (random) 10 ε ε s ε Dipolar (orientation polarization) GHz 10 GHz 100 GHz 1 1 τ = = ω 2π c f c " ε r Cole-Cole Plots (Water) o C 9.14 Increasing f (GHz) o C ε r

9 The Cole-Cole Model ε s ε rd = ε εs ε + 1+ j 1 ( ωτ) α the DC value of dielectric constant The Cole-Cole model is used in determination of user defined standard for coaxial dielectric probe. ε ω = 2πf τ α the infinite frequency dielectric constant the angular frequency the relaxation time constant the relaxation width Measurement Cycle? Fixture ε µ? Software

10 Measurement Instruments LCR Meters and Impedance Analyzers Impedance/Material Analyzer Network Analyzers Auto-Balancing Bridge H MUT L R 2 Fixture I 2 V 1 V 2 V1 V1R Z = = I V 2 2 2

11 LCR Meter/Impedance Analyzer HP 4263B, 4284A, 4285A and 4278A LCR meters HP 4192A and 4194A impedance/gain-phase analyzers 5 Hz to 40 MHz Measures impedance, phase, R, L, C, D, etc. High impedance measurement environment High resolution and accuracy Frequency single (LCR meter) swept (impedance analyzer) Simple and inexpensive Impedance/Material Analyzer HP 4291A 1 MHz to 1.8 GHz Calculates and Displays Material Parameters (ε,µ) vs frequency, temperature Measure Impedance, phase, R, L, C, D, etc. High Resolution and Accuracy Ease of Use

12 MW Frequency Concerns Low frequency Large wavelength vs. MW frequency Small wavelength Lumped element Transmission line Simple Low cost Complex Expensive Network Analyzer Source Receiver Reflected Transmitted Fixture MUT

13 Measurement Calibration Calibration is always important, but at high frequencies measurement errors can be more significant Calibration eliminates systematic (stable, repeatable) errors, but not random errors noise, drift, or environment temperature, humidity, pressure Measurements more susceptible to small changes in system Minimize errors with good measurement practices visually inspect connectors for dirt/damage minimize physical movement of test port cables Network Analyzer HP 8753, 8720 and 8510 family of network analyzers 300 khz to 110 GHz Measures reflection/transmission (magnitude and phase) vs. frequency High accuracy 50 ohm measurement environment

14 HP Instrument Summary HP 8753E Network analyzers HP 8720D HP 8510C HP 4192A, 4194A, 4263B, 4284A, 4285A, 4278A HP 4291B Impedance/Material Analyzer LCR meters Impedance analyzers DC f (Hz) Measurement Techniques Parallel Plate Coaxial probe Transmission line Free-space Resonant cavity

15 CH1 S11 1 U FS Cor Hid START N MH Z LOG MA G PHASE DELA Y SMIT CHARH T POLA R LIN MA G SWR MO R E Parallel Plate r ε = C A ε0 t tanδ = D mm < 10 mm Liquids LF Parallel Plate System LCR Meter or Impedance Analyzer (HP 4192A, 4194A, 4263B, 4284A, 4285A or 4287A) HP 16451B Dielectric Test Fixture

16 O LINE +30dBm Max 0Vm Max Scale Ref Sweep Start Center ACTIVE CHA NNEL Ch 1 Ch 2 MEASUREMENT Meas Format Display AVO ID STATIC DISCH ARG E Bw/ Avg SWEEP Source Stop Span Cal Trigger Entry Off Marker Search MA RK ER Back Space Marker Utility ENT RY System Copy INSTRU MENT STATE Local Save Rmt G/n M/ k/m x1 Preset Recall LF Parallel Plate System (Liquid) LCR Meter or Impedance Analyzer (4194A, 4284A, 4285A) 4TP HP 16048A (Normal) PN (High Temp.) HP 16452A Liquid Test Fixture RF Parallel Plate System HP 4291A RF Impedance/Material Analyzer 4291A 1MHz - 1.8GHz HP IMPEDANCE/MATERIAL ANALYZER HP 16143A Dielectric Material Test Fixture. Test Head

17 LF Parallel Plate Summary Relatively simple computation of ε r from C and D Inexpensive Frequency limited to < 100 MHz Does not provide µ r Works well for thin sheets, PC boards, films, etc. Accurate: typically ±1% for ε r, and 5% ± for tanδ RF Parallel Plate Summary Automatic computation of ε r from C and D Frequency limited to 1MHz to 1.8GHz Provides automatic µ r Works well for thin sheets, PC boards, films, etc. Sample must be flat, smooth sheet Accurate: typically ±8% for ε r < 10, and ± for tanδ

18 CH1 S11 1 U FS Co r Hi d START N MH Z LOG MA G PHAS E DELA Y SMIT CHA H RT POLA R LIN MA G SW R MO R E Coaxial Probe Solids Reflection (S ) 11 Liquids S 11 ε r Dielectric Probe System Computer HP Vectra PC (MS-DOS) or Network Analyzer HP 9000 Series 300 (HP BASIC) HP 8752, 8753, 8719, 8720, 8722 or 8510 HP-IB HP 85070B Dielectric Probe HP 85070B Software (Included with probe kit)

19 &RD[LDO3UREH7HFKQLTXH Reflection (S 11) Material assumptions: "infinite" thickness non-magnetic isotropic and homogeneous flat surface no air gaps Method features Broadband Simple and convenient (Nondestructive) Limited ε r accuracy and tanδ low loss resolution Best for liquids or semi-solids &RD[LDO3UREH0RGHO Y L jωcεr ω " Cε r Gr φ ε r ε r " Radiation Higher ε r Lower ε r log f

20 &RD[LDO3UREH&DOLEUDWLRQ Three term calibration (1-port) corrects Directivity Tracking Source match Measure three known standards Open ε r = 1 Γ = 1 Short Γ = 1 User-defined standard (usually water) Difference in predicted and actual value is used to correct measurement &RD[LDO3UREH(UURUV Cable stability Allow time for cable to stabilize Minimize cable flexing Air gaps Machine a flat sample face Probe flatness ~ 100 µ inches Sample thickness Recommended minimum thickness tmin = 20 ε r ( mm)

21 &DEOH3KDVH6WDELOLW\ ε r 1.4 Remeasuring Air at Various Cable Positions f (GHz) e 00 e 10 e 01 e 11 Refresh Calibration If the perturbation is small, the change can be characterized by the measurement of a single cal standard Γ m Γ m = e 00 c 10 Γ a c 01 e10e01 c10 c01γa + 1 e c c Γ = Directivity error = Source match error e10 e01= Reflection tracking error c = Perturbation term 01 Γ m = Measured S11 Γ a = Actual S11 e 00 e 11 c a

22 Refresh Calibration Standards Permittivity of Water at 55 o C ε r 80 Room Temp Cal Short Refresh Air Refresh 55 o C Cal 80 ε r " (GHz) f Errors for Thin Materials %-Error +20% +10% +5% NOM -5% -10% -20% Foam- Backed Metal- Backed 1 t = t 7 1 t = t 2 min min Measurements of Stacks of Paper Paper ε r t = 2.4 tanδ = 0.06 min = 20 ε r Thickness (mm)

23 Coaxial Probe Typical Accuracy εr (%) ε r = 2,5,20,50, fmax = GHz 0.12 ε r ± tanδ f (GHz) Relative Measurements ε r 4.0 Kynar Probe Kynar 7mm T/R Rexolite Probe Kynar-Rex f (GHz)

24 Relative Measurements ε r " 0.6 Kynar Probe Kynar 7mm T/R Rexolite Probe Kynar-Rex f (GHz) &RD[LDO3UREH&RQILJXUDWLRQV HP 85071B materials measurement software HP 85070B High-temperature dielectric probe kit 200 MHz to 20 GHz Temperature range of -40 to +200 o C HP 85070M Dielectric measurement system probe network analyzer computer

25 Coaxial Probe Summary Convenient, easy to use Little or no sample preparation Nondestructive for many materials Ideal for liquids or semisolids Broad frequency range (.2-20 GHz depending on ε r ) Requires sample thickness of > 1 cm (typical Solids must have a flat surface Limited accuracy in ε r ( + 5%) and low loss resolution ( +.05 in tanδ) Not suited to high ε r low ε r materials Does not provide µ r

26 Transmission Line Technique Waveguide Coax Material assumptions: sample fills fixture cross section no air gaps at fixture walls smooth, flat faces, perpendicular to long axis homogeneous Method features: Broadband - low end limited by practical sample length Limited low loss resolution Measures magnetic materials Anisotropic materials can be measured in waveguide Coaxial line supports planar TEM mode (free space) Transmission Line Waveguide l Coax Reflection (S 11) Transmission (S ) 21 S 11 S 22 ε r µ r

27 CH1 S11 1 U FS Co r Hi d START N MH Z LOG MA G PHAS E DEL AY SMIT CHA H RT POLA R LIN MA G SW R MO R E Transmission Line System Computer Network Analyzer HP Vectra PC (MS-DOS) or HP 9000 Series 300 (HP BASIC) HP 8752, 8753, 8719, 8720, 8722 or 8510 HP-IB HP 85071B Materials Measurement Software Transmission Line Fixture (coaxial or waveguide) 7UDQVPLVVLRQ/LQH$OJRULWKPV Optimum Algorithm Measured Output Length Nicolson-Ross S 11,S 21,S 12,S 22 λ g /4 ε r and µ r (PN ) (or S 11,S 21 ) Precision (NIST) S 11,S 21,S 12,S 22 nλ g /4 ε r Fast S 11,S 21,S 12,S 22 nλ g /4 ε r (or S 11,S 21 ) Short-circuited S 11 λ g /2 ε r back Arbitrary dielectric S 11 λ g /2 ε r back

28 $OJRULWKP6HOHFWLRQ Algorithm Nicolson-Ross Precision (NIST) Fast Short-circuited back Arbitrary dielectric back Best fit for Magnetic, short or lossy MUTs. Fastest computation speed. Long, low-loss MUTs. Highest accuracy with no discontinuities. Long, low-loss MUTs Similar to Precision but faster and better for lossy MUTs Liquids, powders Thin films Precision (NIST) Algorithm ε r PTFE in WR-90 (l = cm) Nicolson-Ross Precision (NIST) D GHz 12.4 GHz f (GHz)

29 7UDQVPLVVLRQ/LQH&DOLEUDWLRQ Frequency response calibration Open, short or thru only One-port reflection calibration (3 term error correction) Open (offset short)/short/load (fixed, sliding, offset) Full two-port calibration (12 term error correction) Open (offset short)/short/load (fixed, sliding, offset)/thru Thru/Reflect/Line (HP 8510 only) Offset/Line standard doubles as sample holder /RDG&DOLEUDWLRQ Fixed load D Γ L D m Sliding load Load element D Γ L Offset load Γ L Offset D θ Γ Offset L

30 75/&DOLEUDWLRQ Thru - Zero or non-zero length Port 1 Port 2 Reflect Port 1 - Unknown high reflect - Same response to Port 1 and 2 Port 2 Line - Different in length than "Thru" - Reflectionless Port 1 Port 2 75/&DOLEUDWLRQ5HVLGXDO(UURUV Fewer known standards required Simple standards (especially for non-coaxial media) Highest precision Residual Errors Fixed Load Sliding Load Offset Load TRL Directivity -40 db -52 db -60 db -60 db Match -35 db -41 db -42 db -60 db Tracking 0.1 db db db 0 db

31 7LPH'RPDLQ*DWLQJ Remove mismatches or re-reflections Calibrate when no calibration standards are available 1. Calibrate in a known connector type 2. Connect cable or adapters 3. Connect SHORT Apply time domain gate to SHORT response 4. Normalize with TDR gate ON Add phase offset of 180 degrees 5. For transmission, normalize to THRU response Time Domain Gating Time domain response Frequency domain response Gated Ungated Ungated Gated

32 Sample Length Minimum length S 21 phase shift >> S 21 uncertainty (approx. 20 o ) L min > λ g Maximum length Avoid drop-outs in Nicolson-Ross algorithm Sample loss Long samples may create multiple roots L max λg < 2 Optimum length for low loss materials For Nicolson-Ross: L = λg 4 S 11 = ( max) For Precision or Fast: λ g = n L 2 S 21 = ( max) Wavelength Equations Wavelength of free space λ 0 c = = f 300mm f ( in GHz) Waveguide wavelength λ = g r 1 r ε µ 1 λ λ 0 c λ c = cutoff frequency for waveguide Phase shift g o ( ) L φ = 360 λ

33 ε r 5 Precision/Fast Algorithms cm Rexolite in X band 4 Seed = Seed = 3.0 Seed = 2.5 Seed = Iterative technique avoids drop-outs in long samples f (GHz) Solution converges differently depending on initial seed - ambiguity in number of compete wavelengths in material Separation between solutions decreases with longer samples Choosing Initial Seed Values S 11 Initial seed value equation for coaxial transmission line (initial guess for waveguide): ε r = c ( f f ) 2L c = speed of light (vacuum) L = sample length f = frequency of S null 1 11 f 2= frequency of adjacent S null 11 f = cutoff frequency (waveguide) c f 1 f 2 For waveguide, use initial guess in transcendental equation: ε r = 2L 2 2 f 2 c f ε r c 2 1 f 2 c f ε r 2 May take several iterations

34 6DPSOH+ROGHU/HQJWK/RVV Use sample holder as THRU calibration standard (coaxial) Modify cal kit definition: L offset delay = holder ε r air c Thru Include sample holder as part of Port 2 (waveguide) Define: sample holder length = 0 Port 1 Port 2 Transmission Line Air Gaps (Altschuler, 1963) d b d 1 d 2 d 3 d 4 a neglect gaps along a c ε = ε m L 3 where L 2 εm L 1 d2 d L 1 = log + log d d 1 tanδ 4 3 L tanδm 1 + εc L = 1 c 2 d L 3 = log 4 d 1 d L 2 = log 3 d 2 c ε = ε where m d D tan δ = tan c δ m ( b d) D b εm = b D

35 Typical Errors Caused By Air Gaps Permittivity of material High ε r materials in coaxial lines = 20% to 50% Size of transmission line For ε r = 10 and air gap = 0.25 mm (coaxial line) Coaxial line dimensions 3.0 mm 7.0 mm 14.0 mm 25.0 mm in in Error 35% 14% 8% 4% 3.2% 1.7% Transmission Line Errors Sources of error Network analyzer errors Sample length uncertainty Air gaps between sample and fixture Careful calibration Use good standards Use TRL or time domain gating Measure length precisely Use larger fixture Focus on fit of center conductor (coaxial) or on fit of broadband wall (waveguide) Measure gap precisely and correct in software Fill gap with conductive grease Metalize sample sides

36 Transmission Line Typical Accuracy r r ε = 1 3 ε = 3 10 = Coaxial line 2% 5% 10% Waveguide 1% 3% 5% ε r For low loss, nonmagnetic, isotropic, rigid material Requires precise sample machining (e.g mm) Reported 2-4 times better accuracy with no air gaps Coaxial Transmission Line Fixtures HP coaxial transmission lines - Type-N, 7 mm, 3.5 mm and 2.4 mm Damaskos coaxial line platform - "clam-shell" design in 1.5", 14 mm and 7 mm Damaskos coaxial compactor - 1.5" short-backed fixture for powders and liquids Damaskos square coaxial line - anisotropic or square periodic repeating samples Inter-Continental Microwave materials measurement fixture - 7 mm mainframe and sample cells Maury Microwave coaxial transmission lines - 14 mm, Type-N and 7 mm

37 :DYHJXLGH7UDQVPLVVLRQ/LQH)L[WXUHV HP coaxial waveguide components - X/P/K/R/Q/U/V/W 11644A calibration kits ( λ /4 line) Damaskos waveguide platform - C/X/Ku band two-piece clamp design Damaskos high temperature waveguide measurement system - C band up to 1000 o F Flann Microwave waveguide fixtures - X band cell with removeable top plate and gauging rods Maury Microwave waveguide sections - R/D/S/E/G/F/C/H/X/M/P/N/K/U band straight sections Transmission Line Summary Provides both ε r and µ r Frequency limited to >100 MHz (banded in waveguide) Simple fixtures Precise sample shape required (usually destructive) Broad frequency range ( GHz) Adaptable to "free space" Limited low loss resolution Liquids and gases must be contained

38 Free Space Technique Material assumptions: large, flat, parallel-faced samples ( > 10λ) homogeneous Method features: Non-contacting, non-destructive High frequency - low end limited by practical sample size Useful for high temperature Antenna polarization may be varied for anisotropic materials Measures magnetic materials Free Space Methods Reflection RCS RCS (Radar Cross Section) NRL arch Transmission Tunnel S-parameter (reflection/transmission) NRL Arch Tunnel Cavity Open (Fabry-Perot) resonator S 11 S 21 ε r µ r

39 5DGDU&URVV6HFWLRQ5&6 Sample RCS (dbsm) = 10 log[rcs (m 2 )] = db below a square meter Measures how large the object looks to radar Monostatic, bistatic, quasi-monostatic configurations NRL Arch Dual polarization horns Sample Metal surface Reflectivity Small arch of constant radius Measure reflection from sample compared to flat metal surface

40 Free Space Tunnel Sample Transmit horn Receive horn 2 2d > λ Complex tranmsission coefficient (magnitude and phase) yields ε r Antenna should be 2d 2 /λ from the sample to maintain a planar "far-field" wavefront (where d is the larger of the antenna or sample diameter) Free Space S-parameter To Port 1 of network analyzer Material Sample To Port 2 of network analyzer Plane wave incident on homogeneous sample of infinite transverse dimensions Focussing lenses convert spherical waves to plane waves

41 Free Space High Temperature Heating panels Furnace Thermal insulation Sample No tolerance requirements on sample Thermocouple Sample is easily thermally isolated Fibrous insulation virtually transparent to microwaves Free Space Calibration Response calibration (reflection) Response and isolation calibration (transmission) TRL/TRM 2-port calibration (HP 8510 or 8720) - Thru: focal points are coincident - Reflect: metal plate at focal point - Line or Match: focal points separated by λ/4 or use absorber as a match Time domain gating eliminates multiple reflections Correction factors for defocussing effect

42 Time Domain Response Ungated Gated TDR Gated Frequency Response Removes fine grain response caused by re-reflections Gated Ungated

43 Free Space Sources of Error Sample - finite size - contact with conducting backplane Non-planewave illumination Accuracy/calibration of microwave receiver Mechanical stabilty/alignment of sample and antennae Quality of anechoic environment Free Space Typical Accuracy Typical acccuracy ε = ±1 5% tan δ < ± r Difficult to measure loss of thin ( < 1λ) and low loss ( tanδ < 0.01) samples

44 Free Space Fixtures Damaskos free space arch measurement system - 2 to 18 GHz horns - angle of incidence varies from 10 to 60 degrees - dual polarization horns HVS free space EM materials measurement system GHz to >40 GHz in six bands - Focussing lenses maintain a plane "far-field" wavefront - Temperatures to +850 o C Open Resonator (Fabry-Perot) Input Output Sample Concave mirror Input Output Plane mirror Hemispherical Sample Concave mirror Full Confocal Concave mirror Generates Gaussian beam TEM mode ε r and tanδ are obtained from change in f c and Q Accurate for low loss (tanδ < 0.01) homogeneous material

45 Hi d CH1 S11 1 U FS C or START N MHZ LOG MA G PHA SE DEL AY SMI CHA TH RT POL AR LIN MA G SW R MO RE Open Resonator (Fabry-Perot) Large, flat, parallel faced samples Sensitive to low loss and thin film materials Commonly used at high frequencies (mm-wave and above) Not suited to high temperatures - Cavity is sensitive to thermal effects Free Space System Computer HP Vectra PC (MS-DOS) or HP 9000 Series 300 (HP BASIC) Network Analyzer HP 8752, 8753, 8719, 8720, 8722 or 8510 HP-IB HP 85071B Materials Measurement Software Antennae

46 Free Space Summary Noncontacting, often nondestructive Sample not contained Useful for high temperatures Remote sensing Special calibration considerations Requires connectorless standards (TRL, LRM) Tightly controlled distance from antenna to sample Time domain gating can eliminate mismatch error Requires large, flat, thin, parallel faced sample Resonant Cavity RF Connector MUT Q S Q 0 Support Iris-coupled end plates f f S f C Sample f Q ε r or µ r

47 Resonator (absolute) Cavity Methods TE 01n cavity Sample fills a significant portion of cavity volume. Exact theories applied to cavities for low loss materials. Cavity perturbation Transmission line (waveguide) cavity Sample disturbs (without changing) fields in cavity. f < 0.1% (recommended) Measure shift in resonant frequency and Q. TE 01n Cavity Piston for tuning E Small coupling apertures (to waveguide) Helical wavegude Electric field Disc sample n λ Sample diameter same as cavity, wavelengths thick 2 Helical waveguide prevents TM 11 mode

48 Transmission Line Cavity Iris-coupled end plates Based on ASTM 2520 E-field Sample Rectangular waveguide cavity propagates TE 10n mode Sample placed parallel to cavity E-field Fibers may be inserted through a fused silica rod Cavity Perturbation Algorithm ASTM 2520 Method For a vertical rod or bar sample inserted in a TE 10n rectangular waveguide resonant cavity sample inserted Q s empty cavity Q c ( f f ) Vc c ε r = 2V f s s V c is the volume of s V c 1 1 ε r" = 4V s Qs Qc the sample f s f c f V s is the volume of the empty cavity s

49 Harmonic Stripline Cavity Center conductor Permittivity E-field maximum Sample Permeability H-field maximum Ground plane Single frequency - Cavity size sets fundamental frequency (also resonates at integer multiples) Ideal for small, thin, rectangular solid samples Cavity Sources of Error Network analyzer frequency resolution Sample dimension uncertainty Approximations in analysis

50 Top Cavity Accuracy Results from NIST TE 01n Resonator Cavity Accuracy ε = ± 0.2% to ± 0.4% r tanδ = ± Dominant TE 01n modes, all other modes attenuated >25 db Unloaded Q = 83,000 Temperature controlled to within C o Cavity Fixtures HP waveguide components X/P/K/R/Q/U/V/W 11644A calibration kits (standard section) ASTM standard D-2520 Damaskos harmonic stripline cavity system 100, 250 and 500 MHz fundamentals

51 CH1 S11 1 U FS Co r Hi d START N MHZ LOG MA G PHAS E DEL AY SMI CHA TH RT POL AR LIN MA G SW R MO RE Resonant Cavity System Computer Network Analyzer HP Vectra PC (MS-DOS) or HP 9000 Series 300 (HP BASIC) HP 8752, 8753, 8719, 8720, 8722 or 8510 HP-IB Iris-coupled end plates Sample Software Cavity Fixture Sample Cavity Summary Very accurate Does not provide broadband frequency data Very sensitive to low loss (to 10-6 for some cavities) Precise sample shape required (usually destructive) Analysis may be complex

52 Summary of Techniques Loss Coaxial Probe High Transmission Line Medium Free Space Low Parallel Plate Resonant Cavity Open Resonator Fabry-Perot 50 MHz 5 GHz 20 GHz 40 GHz 60 GHz Low frequency RF Microwave Millimeter-wave Frequency Measurement Technique Summary Free Space Cavity Transmission Line Coaxial Probe Parallel plate DC Frequency (Hz) 10 12

53 Parallel Plate Summary of Techniques ε r Accurate Best for low frequencies; thin, flat sheets Coaxial Probe ε r Broadband, convenient, non-destructive Best for lossy MUTs; liquids or semi-solids Transmission Line ε r and µ r Resonant Cavity ε r and µ r Free Space ε r and µ r Broadband Best for lossy MUTs; machineable solids Accurate Best for low loss MUTs; small samples Non-contacting Best for high temperatures; large, flat samples HP Instruments and Fixtures HP 16451B HP 16452A Transmission line software HP 85071B Dielectric probe HP 85070B HP 16143A Dielectric material test fixture Dielectric test fixture Liquid test fixture DC 10Hz 100Hz 1kHz 10kHz 100kHz 1MHz 10MHz 100MHz 1GHz 10GHz 100GHz HP 4192A, 4194A, 4263A, 4284A, 4285A, 4278A HP 4291A LCR meters/impedance analyzers Impedance/Material Analyzer HP 8753C Network analyzers HP 8720C HP 8510C

54 It depends on: Which Technique is Best? Frequency range Expected value of ε r and µ r Required measurement accuracy Material properties (i.e., homogeneous, isotropic) Form of material (i.e., liquid, powder, solid, sheet) Sample size restrictions Destructive or nondestructive Contacting or noncontacting Temperature Cost And more...

55 Dielectric Mechanisms vs. Frequency + ε r Dipolar Ionic - Atomic - Electronic ε r f MW IR V UV 1