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ABSTRACT: The microwave dielectric properties of single-crystal LiF, CaF<sub>2</sub>, MgF<sub>2</sub>, BaF<sub>2</sub>, and SrF<sub>2</sub>, synthesized by Stockbarger melt-growth techniques, are measured using cylindrical specimens as TE<sub>01δ</sub> dielectric resonators enclosed in a cylindrical cavity. Single-crystal permittivity and dielectric loss tangent were evaluated at fixed frequencies between 7 and 9 GHz and over a temperature range from -75 to 150°C. The real permittivities of the measured fluorides increase quasi-linearly with temperature, permitting evaluation of the thermal coefficients of permittivity. The dielectric loss tangents increase approximately linearly with frequency, so that Qf (GHz) products at room temperature for BaF<sub>2</sub>, SrF<sub>2</sub>, CaF<sub>2</sub>, LiF, and MgF<sub>2</sub> (normal to c-axis) are 57600, 73000, 92000, 192400, and 458600, respectively. The dielectric data supports existing ion polarizabilities that are used with molar volumes and molecular additivity rules to estimate the permittivities of more complex fluorides whose values have not been experimentally determined.
Electrical Insulation and Dielectric Phenomena, 2004. CEIDP '04. 2004 Annual Report Conference on; 11/2004
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ABSTRACT: Closed-form analytical solutions are derived for accurate
microwave dielectric characterization of rod test specimens inserted
into dielectric sleeve resonators placed centrally in a metal cavity.
Low-loss sleeve resonators can be used advantageously for multiple
frequency measurements of the same specimen and may be employed for
accurate dielectric characterization of high-permittivity specimens
having dielectric loss factors greater than 0.001. Uncertainty relations
for permittivity and dielectric loss are also shown, which demonstrate
that when sample electric energy filling factors are greater than 0.4,
relative uncertainties in measured permittivity and dielectric loss
tangent are less than 1% and 4%, even for relative permittivities
greater than 600. Example measurements are given that illustrate how
this dielectric resonator system can be employed for dielectric
characterization of ferroelectric materials at temperatures both near or
far from their Curie temperatures
IEEE Transactions on Instrumentation and Measurement 05/2002; · 1.21 Impact Factor
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ABSTRACT: Low-loss sleeve resonators can be used for accurate microwave
dielectric characterization of rod-shaped test specimens. The test
specimen is inserted into the dielectric sleeve resonator and placed
centrally in a metal cavity. With the use of additional sleeve
resonators having differing external diameters or permittivities, a
single specimen can be characterized at multiple frequencies. Sleeve
resonators can also be employed for accurate dielectric characterization
of high-permittivity specimens having dielectric loss factors greater
than 0.001. Closed-form solutions for TE<sub>0np</sub> resonant mode
structure are given. Uncertainty relations for permittivity and
dielectric loss are also shown, which demonstrate that when sample
electric energy filling factors are greater than 0.4, relative
uncertainties in measured permittivity and dielectric loss tangent are
less than 1% and 4%, even for relative permittivities greater than 600.
Example measurements are given that illustrate how this dielectric
resonator system can be employed for dielectric characterization of
ferroelectric materials at temperatures both near or far from their
Curie temperatures
Microwave Symposium Digest, 2002 IEEE MTT-S International; 02/2002
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ABSTRACT: A general Sommerfeld integral formulation is given for the
electromagnetic (EM) fields of an oscillating vertical magnetic or
electric dipole over an electrically inhomogeneous thin sheet. The
electrical properties of the sheet are characterized by a conductance
function that is an arbitrary function of spatial coordinates. When the
conductance function has axial symmetry relative to the source dipole,
the general solution form simplifies to a Fredholm integral equation of
the third kind. The general solution is shown to reduce to the special
case of an infinite sheet having uniform conductance. When the sheet
conductance is either uniform or varies linearly, the field expressions
show an algebraic dependence on the conductance. For a general
inhomogeneous conductance distribution, the field dependence is not
algebraic
IEEE Transactions on Antennas and Propagation 11/2000; · 2.15 Impact Factor
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ABSTRACT: The permittivity and dielectric loss tangent of bulk strontium
titanate were measured from 4 to 300 K, at frequencies from 400 MHz to
3.8 GHz, using a dielectric rod-resonator technique. Single-crystal and
ceramic SrTiO<sub>3</sub> samples were both investigated. Significant
differences in permittivity and losses were observed between
single-crystal and ceramic materials at cryogenic temperatures. When
measured at liquid nitrogen temperatures, the single-crystal sample
dielectric loss tangent was approximately 10<sup>-4</sup>
Microwaves, Radar and Wireless Communications. 2000. MIKON-2000. 13th International Conference on; 02/2000
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ABSTRACT: Whispering-gallery modes are used for very accurate permittivity,
dielectric loss, and temperature coefficient of permittivity
measurements for both isotropic and uniaxially anisotropic dielectric
materials. The relationship between resonant frequencies, dimensions of
the resonant structure, and permittivity of the sample under test is
calculated with a radial mode-matching technique. The relative accuracy
of these computations is better then 10<sup>-4</sup>. The influence of
conductor losses on dielectric loss tangent determination is treated for
both whispering-gallery-mode and TE<sub>01δ</sub>-mode
dielectric-resonator techniques. Two permittivity tensor components of
sapphire and their temperature dependence were measured from 4.2 to 300
K. The total uncertainty in permittivity when use is made of
whispering-gallery modes was estimated to be less than 0.05%. The
uncertainty was limited principally by uncertainty in sample dimensions.
Experimental and calculated resonant frequencies of several
whispering-gallery modes differed by no more than 0.01%. The dielectric
loss tangent of sapphire parallel and perpendicular to its anisotropy
axis was calculated to be less than 10<sup>-9</sup> at 4.2 K. The
permittivity and dielectric loss tangent of a commercially available
low-loss high-permittivity ceramic material has also been measured at S-
and C-band frequencies using a large number of whispering-gallery modes
IEEE Transactions on Microwave Theory and Techniques 07/1999; · 1.85 Impact Factor
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ABSTRACT: Whispering gallery modes were used for very accurate permittivity
and dielectric loss tangent measurements for low loss isotropic and
uniaxially anisotropic materials. We present the measurements of several
specimens including sapphire, YAG, quartz, rutile and
SrLaAlO<sub>4</sub>. The total absolute uncertainty in real part of the
permittivity tensor was estimated to be less than 0.1% and was limited
by the uncertainty in the dimensions of the samples. Imaginary parts of
the permittivity tensor were measured to about 10% accuracy, limited by
the accuracy of Q-factor measurements in whispering gallery modes. The
anisotropy ratio of the measured materials varied from 1 (isotropic YAG)
to 2.2 (rutile). All anisotropic materials exhibited anisotropy in the
imaginary part of the permittivity tensor as well as the real part. For
most crystals dielectric losses can be approximated by a power function
of absolute temperature in only a limited temperature range. At very low
temperatures (4-50 K) properties of both the real and imaginary
permittivity tensor are often affected by impurities which are always
present in real crystals
Frequency and Time Forum, 1999 and the IEEE International Frequency Control Symposium, 1999., Proceedings of the 1999 Joint Meeting of the European; 02/1999
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ABSTRACT: Measurements on low-loss materials using closed and open cavity
resonators, and dielectric resonator methods are presented. Results
indicate that consistent measurement results can be obtained with a
number of well-characterized fixtures. Uncertainties associated with
each method are addressed. Measurements also were performed on materials
used in previous intercomparisons
IEEE Transactions on Dielectrics and Electrical Insulation 09/1998; · 1.09 Impact Factor
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ABSTRACT: Complex scalar permeability measurement results of microwave
ferrites at frequencies from 1 Hz to 20 GHz are presented. Three
different techniques were used to perform the measurements. The method
chosen depended on frequency and magnetic loss. At low frequencies, 1-10
<sup>5</sup> Hz, we applied lumped parameter circuit techniques. With
this technique nonlinear permeability effects were measured. At higher
frequencies, from 1 MHz up to gyromagnetic resonance, coaxial
transmission line techniques were used. At frequencies above
gyromagnetic resonance, a dielectric ring resonator technique was used.
By combining all three methods, the real and imaginary parts of sample
permeability, with magnetic loss factors that vary from 10<sup>-5</sup>
to 10<sup>2</sup>, may be measured. In addition, nonlinear effects in
ferrite materials and saturation magnetization may be evaluated
Microwaves and Radar, 1998. MIKON '98., 12th International Conference on; 06/1998
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ABSTRACT: Whispering-gallery modes are used for very accurate complex
permittivity measurements of both isotropic and uniaxially anisotropic
dielectric materials. A mode-matching technique is used to find the
relationship between the complex permittivity, resonant frequency, and
the dimensions of a resonant structure. The total uncertainty in
permittivity is smaller than 0.05 percent and is limited principally by
uncertainty in sample dimensions
Microwave Symposium Digest, 1997., IEEE MTT-S International; 07/1997
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ABSTRACT: The split dielectric resonator technique makes it possible to
measure the real part of permittivity of isotropic materials for a very
broad permittivity range and dielectric loss tangents in the range from
10<sup>-4</sup> to 10<sup>-1</sup> with high accuracy. For uniaxially
anisotropic materials, the split resonator method permits measurement of
the permittivity and and the dielectric loss tangent in the plane
parallel to the the sample bottoms. Additional measurements using
re-entrant cavity enable determination of permittivity and the
dielectric loss tangent perpendicular to this plane
Dielectric Materials, Measurements and Applications, Seventh International Conference on (Conf. Publ. No. 430); 10/1996
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ABSTRACT: The microwave properties of bulk ceramic barium strontium titanate
and non-ferroelectric oxide composites are measured at X-band with a
cylindrical mode-filtered resonant cavity. A helical wire-wound
waveguide makes up the cavity's cylindrical wall, which permits the use
of high-purity TE<sub>01p</sub> resonant modes for high accuracy
permittivity measurements. Measurement results at 300 K show that
microwave dielectric losses increase as the stoichiometric percentage of
barium increases. The real relative permittivity increases with
decreasing weight percent of added non-ferroelectric low-loss oxide.
Dielectric losses rapidly decrease with the addition of a relatively
small amount of non-ferroelectric oxide
Applications of Ferroelectrics, 1996. ISAF '96., Proceedings of the Tenth IEEE International Symposium on; 09/1996
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ABSTRACT: Whispering-gallery modes in axially magnetized ferrite disk
samples have been studied using rigorous Rayleigh-Ritz and
finite-element analyses. The influence of radial magnetization on the
resonant frequencies of both WGE and WGH modes was investigated, both
theoretically and experimentally. Permeability tensor components of
biased ferrites were determined from measurements of the resonant
frequencies of the WGH<sub>n00</sub> and the WGE<sub>n00</sub> mode
families
IEEE Transactions on Microwave Theory and Techniques 08/1996; · 1.85 Impact Factor
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ABSTRACT: The relative magnetic permeability and loss factor of microwave
ferrites in the demagnetized state are determined near and above
gyromagnetic resonance using low-loss dielectric ring resonators. This
technique allows complex permeability determination on a single ferrite
sample from 2 GHz to 25 GHz. The measured real parts of the initial
permeability are compared with theoretical predictions of the
permeability of a sample in the demagnetized state
Precision Electromagnetic Measurements Digest, 1996 Conference on; 07/1996
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ABSTRACT: A wide variety of microwave ferrite phase-shifting materials have
been measured in the demagnetized state. The relative magnetic
permeability and loss factor were determined near and above natural
gyromagnetic resonance using H<sub>011</sub> cylindrical dielectric ring
resonators. These low-loss dielectric sleeves were dimensioned for
accurate magnetic property measurements of single ferrite rod samples at
logarithmically sampled resonant frequencies from 2 GHz to 25 GHz.
Permeability and magnetic loss factor are computed from the measured
resonant frequencies and Q factors of these resonators, with and without
the ferrite sample, using exact eigenvalue equations. Generally, the
real part of the complex magnetic permeability increases with decreasing
saturation magnetization, while the magnetic loss factor increases
nonlinearly with increasing saturation. Schloemann's theoretical model
for the real part of initial permeability of a cylindrically symmetric
domain configuration in the completely demagnetized state shows
excellent agreement with measured data when
2πγμ<sub>s</sub>/ω<0.75. The data allow design
optimization of circulators and dual-mode and polarization-insensitive
phasers, which are widely used in antenna array systems
IEEE Transactions on Magnetics 06/1996; · 1.36 Impact Factor
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ABSTRACT: The permittivity and dielectric loss tangent of cross-linked
polystyrene (Rexolite), polytetrafluoroethylene (Teflon), and
single-crystal quartz were measured at microwave frequencies and at
temperatures of 77 K and 300 K using a dielectric resonator technique.
Dielectric loss tangents as low as 7×10<sup>-6</sup> at 77 K were
determined by applying high-temperature superconducting (HTS) films as
the endplates of the dielectric resonator. Two permittivity tensor
components for uniaxially anisotropic crystalline quartz were measured.
Although the permittivities at 77 K changed very little from their room
temperature values at 300 K, large changes in dielectric losses were
observed. The decreased losses of these microelectronic substrates can
markedly improve the performance of many microwave devices at cryogenic
temperatures
IEEE Transactions on Instrumentation and Measurement 05/1995; · 1.21 Impact Factor
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ABSTRACT: A review of the most common methods for nondestructive permittivity and permeability measurements is presented. Transmission-line
techniques, coaxial apertures, open resonators, surface-waves, and dielectric resonator methods are examined. Measurements
on bulk, thin materials, and thin films are addressed. Measurement fixtures that can be used as sensors are highlighted. The
frequency range of applicability and typical uncertainties associated with each method are addressed.
Research in Nondestructive Evaluation 04/1995; 7(2):117-136. · 0.68 Impact Factor
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ABSTRACT: The open-ended coaxial probe with lift-off is studied using a
full-wave analysis, and an uncertainty analysis is presented. The field
equations for the following terminations are worked out: (1) the sample
extends to ∞ in the positive axial direction, (2) the sample is
backed by a well-characterized material, and (3) the sample is backed by
a short-circuit termination. The equations are valid for both dielectric
and magnetic materials. The model allows the study of the open-ended
coaxial probe as a nondestructive testing tool. The analysis allows a
study of the effects of air gaps on probe measurements. The reflection
coefficient and phase are studied as a function of lift-off, coaxial
line size, permittivity, permeability, and frequency. Numerical results
indicate that the probe is very sensitive to lift-off. For medium to
high permittivity values and electrically small probes, gaps on the
order of fractions of a millimeter strongly influence the reflection
coefficient. In order for the field to penetrate through the air gap,
larger size coaxial line or higher frequencies need to be used. A
comparison of the theory to experiment is presented. The results are in
close agreement. A differential uncertainty analysis is also included
IEEE Transactions on Instrumentation and Measurement 11/1994; · 1.21 Impact Factor
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ABSTRACT: A dielectric resonator technique has been used for measurements of
the permittivity and dielectric loss tangent of single-crystal
dielectric substrates in the temperature range 20-300 K at microwave
frequencies. Application of superconducting films made it possible to
determine dielectric loss tangents of about 5×10<sup>-7</sup> at
20 K. Two permittivity tensor components for uniaxially anisotropic
samples were measured. Generally, single-crystal samples made of the
same material by different manufacturers or by different processes save
significantly different losses, although they have essentially the same
permittivities. The permittivity of one crystalline ferroelectric
substrate, SrTiO<sub>3</sub>, strongly depends on temperature. This
temperature dependence can affect the performance of ferroelectric
thin-film microwave devices, such as electronically tunable phase
shifters, mixers, delay lines and filters
IEEE Transactions on Microwave Theory and Techniques 11/1994; · 1.85 Impact Factor
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ABSTRACT: A dielectric resonator technique has been used for measurements of the permittivity and dielectric loss tangent of single-crystal dielectric substrates in the temperature range 20--300 K at microwave frequencies. Application of superconducting films made it possible to determine dielectric loss tangents of about 5 [times] 10[sup [minus]7] at 20 K. Two permittivity tensor components for uniaxially anisotropic samples were measured. Generally, single-crystal samples made of the same material by different manufacturers or by different processes have significantly different losses, although they have essentially the same permittivities. The permittivity of one crystalline ferroelectric substrate, SrTiO[sub 3], strongly depends on temperature. This temperature dependence can affect the performance of ferroelectric thin-film microwave devices, such as electronically tunable phase shifters, mixers, delay lines and filters.
IEEE Transactions on Microwave Theory and Techniques (Institute of Electrical and Electronics Engineers); (United States). 09/1994; 42:10.
