DIELECTRIC MEASUREMENTS USING A VECTOR NETWORK ANALYZER FOR GREENLAND AND ANTARCTICA ICE CORE SAMPLES Tyler L. Berry, Fernando Rodriguez-Morales, Stephen Yan, CReSIS, University of Kansas, Lawrence KS 66045, Haskell Indian Nations University, Lawrence

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DIELECTRIC MEASUREMENTS USING A VECTOR NETWORK
ANALYZER FOR GREENLAND AND ANTARCTICA ICE CORE
SAMPLESTyler L. Berry, Fernando
Rodriguez-Morales, Stephen Yan, CReSIS,
University of Kansas, Lawrence KS 66045, Haskell
Indian Nations University, Lawrence KS 66046

• Abstract
• Sea level is strongly linked to the growth and
  shrinkage of the large ice sheets in Greenland
  and Antarctica. There is an urgent need to
  improve both knowledge of ice dynamics and
  accuracy of ice-sheet models to predict the
  ice-sheets response to a warming climate and
  their contribution to sea level rise. A key
  component to improve the ice sheet models through
  the use and interpretation of radar data is the
  knowledge of the dielectric properties of the
  ice. Most of the measured data on the dielectric
  properties of ice available today is based on
  measurements performed at low frequencies with
  the technology available in the 1960s and again
  in the 80s. In this project we will design and
  fabricate a set of test fixtures to characterize
  relative permittivity of dielectric materials
  using a vector network analyzer. One technique to
  be used relies on a planar transmission line in
  contact with the sample, where the sample acts as
  a dielectric loading to the line. By measuring
  the change in the transmission and reflection
  coefficients of the transmission line, the
  relative permittivity of the sample can be
  retrieved. The method will serve as a basis for
  dielectric measurements on dielectric materials
  in the 10-1000 MHz range and will be used as a
  test bench for future measurements on ice cores.

Construction of a Test Bed for Ice Core
Measurement

• Methodology
• The first step was to determine a suitable
  material to create the test stand out of and for
  its dielectric properties to not interfere with
  the measurements of the ice cores. The dielectric
  constant needed to be less than 3.0 but it would
  be more beneficial to be closer to 2.0. We could
  get a rough estimate of materials dielectric
  constants from tables researched on the internet.
  The results had tolerances on some materials too
  wide to make a good estimate on whether they were
  suitable.
• Samples of materials were ordered that had a
  price range suitable for our purposes and then
  prepared to test their dielectric constants.
• Copper tape was covered on one side of the
  material and a 3/8 inch strip of copper tape
  placed down the center on the reverse side (Fig.
  1 and 2).
• A PCB Endlaunch SMA .042 inch Connector was then
  soldered to the sample. The center pin of the SMA
  was soldered to the 3/8 inch strip and the outer
  conductor of the SMA was then soldered to the
  completely covered side (Fig. 3 and 4).
• The information gathered from the Network
  Analyzer was transferred to the Agilent Advanced
  Design System program (ADS) on a computer and the
  dielectric constant of the material was derived.
• The results of the High Density Polyethylene
  (HDPE) (2.16) and the price of materials were
  satisfactory to our purpose and it was decided to
  use this material for our platform.
• The design in SolidWorks Computer Animated
  Design (CAD) was determined after the material
  was selected. The design was determined based on
  material characteristics and material size that
  could be purchased.

Conclusion Further testing is required after the
construction of the test platform to determine if
the material and dimensions will be sufficient.
Test samples will be used in substitution of the
ice cores to see how it well it employs the
return data. After final testing we will use the
measured dielectric data of the ice cores to
simulate radar returns at existing core sites and
compare these returns with experimental results.
We will perform measurements of existing ice
cores in collaboration with Prof. Dorthe
Dahl-Jensen and her team at the University of
Copenhagen. After verifying the performance of
the probe, we will convert the system to perform
measurements in the field on new cores to be
drilled.
Purpose To develop and demonstrate a system for
dielectric measurements in the frequency range of
10-1000 MHz. This system will consist of a
coplanar waveguide test platform (See Test
Platform Model). An ice core sample can be place
on the platform and impedance measurements can be
performed with a vector analyzer. The test
platform will allow characterization of the
samples without further cutting or slicing of the
ice core sample. With the accurate ice
core-derived DEP from the new measurement system,
we can invert existing radar data as well as the
new ultrawideband radar depth sounder (150-600
MHz) that is currently under development by
CReSIS (deployment planned for winter 2013) to
unambiguously determine the basal conditions over
many areas of the Ice Sheets in Greenland and
Antarctica.
References WCRP, Understanding sea-level rise
and variability, Workshop Report. IOC/UNESCO,
Paris, France, June 6-9, 2006. Dahl-Jensen, D.
et al., Eemain interglacial reconstructed from a
Greenland folded ice core, Nature, vol. 493, pp.
489-494, 2013. Van der Veen, C.J. and ISMASS
Members, A Need for More Realistic Ice-Sheet
Models, SCAR Report No.30, 2007. Evans, S.,
Dielectric properties of ice and snow a
review, Journal of Glaciology, vol. 5, no. 42,
pp. 773-792, 1965. Fujita, S., Shiraishi, M.,
and Mae, S., Measurement on the dielectric
properties of acid-doped ice at 9.7 GHz, IEEE
Transactions on Geoscience and Remote Sensing,
vol. 30, no. 4, pp. 799-803, 1992. Wilhelms, F.,
et al., Precise dielectric profiling of ice
cores a new device with improved guarding and
its theory, Journal of Glaciology, vol. 44, no.
146, pp. 171-174, 1998. Havrilla, M. J., and
Nyquist, D. P., Electromagnetic characterization
of layered materials via direct and de-embed
methods, IEEE Transactions on Instrumentation
and Measurement, vol. 55, no. 1, pp. 158-163,
2006.
General Estimation Procedure
ADS Simulated and Tested Results