Characterizing Electromagnetic Properties of Materials. Making Reliable Measurements at mm and Sub-mm Wavelengths

Transcription

1 Characterizing Electromagnetic Properties of Materials at 110GHz and Beyond Jeffrey Hesler Shelley Begley Suren Singh Phil Bartley Virginia Diodes Inc. Agilent Technologies Agilent Technologies IMS

2 Agenda Why Characterize Material Properties? Measurement System Calibration Measurement Results

3 Electromagnetic Materials Radar Absorbing and Stealth Materials Radome Materials Electronic Substrate and Packaging Materials Specific Absorption Rate (SAR) Phantoms Meta-materials

4 Why Materials Characterization? Characterizing Electromagnetic Properties of Materials at 110GHz and beyond Important for: Circuit design Military Applications Car Radar Applications New Materials Research Incoming Inspection Quality Assurance Health and Safety and more

5 Permittivity and Permeability Definitions Permittivity (Dielectric Constant) Permeability κ = ε ε 0 = ε r = ε ' r jε " r μ = μ μ 0 = ' " μ r jμ r interaction of a material in the presence of an external electric field. interaction of a material in the presence of an external magnetic field. \

6 Electromagnetic Field Interaction Electric Fields eds Permittivity ε r = ε ' r jε " r Dielectric Constant STORAGE LOSS MUT STORAGE LOSS μ r Magnetic Fields Permeability = μ ' r jμ " r

7 Loss Tangent '' ε r ε r ε ' r " ε tanδ = r = ' ε ε r κ" κ ' tanδ = 1 D = = Q Energy Lost per Cycle Energy Stored per Cycle D Dissipation Factor Q Quality Factor

8 Measurement Techniques vs. Frequency and Material Loss Loss High Coaxial Probe Transmission line Medium Parallel Plate Free Space Low Resonant Cavity Frequency 50 MHz 5 GHz 20 GHz 40 GHz 60 GHz 750+ GHz RF Microwave mm/submm-wave

9 Transmission Free-Space l Material assumptions: Flat parallel faced samples Sample in non-reactive region Beam spot is contained in sample Known thickness > 20/360 Reflection (S11 ) Transmission (S21 )

10 mm-submm Wave System Agilent PNA-X dual source network analyzer Virginia Diodes Inc. Transmit and Receive (TR) Frequency Extenders Sample in holder between two antennae Agilent Materials Measurement Software with Free Space Calibration

11 mm-submm Wave System Photo

12 mm-submm Wave System Photo

13 VDI Frequency Extenders & Horns VDI offers frequency extenders from 75GHz through 750GHz with outstanding dynamic range.

14 PNA-X mmwave Setup

15 Calibration is Required Before a measurement can be made, a calibration must be performed to remove systematic errors.

16 TRM Calibration Thru Reflect Match

17 TRL Calibration Thru Reflect Move the antenna away to compensate for the thickness of the short. Move it back for the next step. Line Move the antenna away on a quarter-wavelength and then back in the original position.

18 Gated Reflect Line (GRL) Calibration Two Tiered Calibration Two port calibration at waveguide or coax input into antennas removes errors associated with network analyzer and cables. ECal, SOLT or TRL Cal done here

19 Gated Reflect Line (GRL) Calibration Two Tiered Calibration Two additional free space calibration standards d remove errors from antennas and fixture. Line (empty fixture) Reflect (metal plate of known thickness)

20 GRL Cal Error Model forward only 2-port Cal Terms 1 MUT S21 2-port Cal Terms Tt D Ms GRL Error Adapter S11 S22 GRL Error Adapter Ml Tr S12 Coax or Waveguide 2-port Cal corrects errors from end of cable back into the instrument.

21 GRL Cal Error Model forward only 2-port Cal Terms 1 MUT S21 2-port Cal Terms Tt D Ms GRL Error Adapter S11 S22 GRL Error Adapter Ml Tr S12 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.

22 GRL Cal Error Model MUT O21 S21 T12 O11 O22 S11 S22 T22 T11 O12 S12 T21 Six Unknowns O21 = O12 O11 O22 T21 = T12 T11 T22 Need Three Standards!

23 Gated Standard S11 Time Domain - Empty Fixture 3201 points used to avoid aliasing Min Points = 1 + Alias Free Range (s) * Frequency Span (Hz) time domain gate includes only reflections before sample Mag(S) (db) Transmitting Antenna Receiving Antenna sample holder S11 (db) Time (ns) Linear (S11 (db))

24 GRL Cal Error Model MUT O21 S21 T12 O22 S11 S22 T22 O12 S12 T21 Four Unknowns O21 = O12 O22 T21 = T12 T22

25 Metal Plate Standard P 11 = P 22 = -1 O21 MUT S21 T12 P 21 =P 12 =0. O22 S11 S22 T22 O O Γ plate_1 = 1 + O22 O12 S12 T21 TT Γ = plate_2 1 + T 22

26 Line Standard A 11 =A 22 =0 O21 MUT S21 T12 A 21 = A 12 = j ud e ω ε O22 S11 S22 T22 ω= frequency ε= permittivity of air μ= permeability of air. d= thickness of the metal plate O12 S12 T21 Γ = air_1 Γ = air_2 A A O O T 1 O T A A T T O 1 T O

27 GRL Cal Error Model forward only 2-port Cal Terms MUT 2-port Cal Terms 1 S21 Tt D Ms GRL Error Adapter S11 S22 Calibration planes GRL Error are at the surface Ml of Adapter the metal plate. Tr S12 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.

28 Transmission Models Algorithm Measured S-parameters Output Nicolson-Ross S11,S21,S12,S22 ε r and μ r NIST Precision S11,S21,S12,S22 ε r Fast S21,S12S12 ε r Poly Fit S11,S21,S12,S22S21 S12 S22 ε r and μ r Stack Two S21,S12 (two samples) ε r and dμμ r

29 Measurement Results

30 Measurement Results

31 Measurement Results Multiple solutions can occur when sample is thicker than 1 wavelength The correct solution is obtained by giving a permittivity estimate sample is 2.36mm thick

32 Measurement Results

33 Future Work Try again with Thomas Keating horns made for Quasioptical table. Method for determining number phase rotations in sample. Model for low loss samples.

34 Thank You

35 References R N Clarke (Ed.), A Guide to the Characterisation of Dielectric Materials at RF and Microwave Frequencies, Published by The Institute of Measurement & Control (UK) & NPL, 2003 J. Baker-Jarvis, M.D. Janezic, RF R.F. Riddle, R.T. RT 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 Basics of Measuring the Dielectric Properties of Materials. Agilent application note EN, April 28, 2005 Deepak K. Ghodgaonkar et al; Free Space Method for Measurement of Dielectric Constants and Loss Tangents at Microwave Frequencies ; IEEE Transactions on IM volume 37 number 3, June P. Bartley, S. Begley, Improved Free-Space S-Parameter Calibration IMTC 2005 Instrumentation and Measurement Technology Conference Ottawa, Canada, May 2005