Title of Invention

AN APPARATUS AND METHOD FOR MEASURING AND MONITORING COMPLEX PERMITTIVITY OF MATERIALS.

Abstract TITLE: AN APPARATUS AND METHOD FOR MEASURING AND MONITORING COMPLEX PERMITTIVITY OF MATERIALS. An instrument for the measurement of complex permitivity of dielectric materials in solid, liquid and semisolid state comprising: a microwave resonator selected from the group of transmission and reflection reasonators, said microwave resonator having a resonator surface; a microwave sweep oscillator, the putput of which is coupled to the microwave resonator; a detector associated with the microwave resonator for detecting a frequency shift and a q factor of the microwave resonator; means for coupling power to and fromt he microwave resonator; means for measuring the power supplied to and received from the microwave resonator; a computer interfaced with a system with components including the microwave sweep osicllator, the microwave resonator, the detector and the means for measuring the power; electromagnetic software for the analysis of complex permitivity of the dielectric materials; and an inerfacing software for communication between components of the system and the computer.
Full Text FIELD OF INVENTION
This invention relates to an apparatus and method for measuring
and monitoring complex permittivity of materials.
PRIOR ART
Microstrip and microstrip type resonators described are efficient
devices for measuring complex permittivity of materials at
microwave frequencies as disclosed by Flemming U.S. Patent No.
4,829,233; by Heath U.S. Patent No.3,510,764; and by Gerhard
U.S. Patent No.3,942,107 and by King U.S. Patent No.5,334,941.
Flemming describes a method in which a resonator is mounted
on the copper-backed substrate. A resonator is weekly coupled
to a microwave feed source and to a microwave detector so that
the resonator Q factor is unaffected by the impedance"s of the
source or the detector. When the test dielectric is placed near
the resonator, the electromagnetic fields near the resonator
are coupled to the material under test so as to affect the
resonator frequency of resonance as well as Q factor.
The resonant frequency and Q factor measurements are done in
the transmission mode. Further the methods for modulating source
or resonant frequency "are disclosed which avoids the need for
the swept source.
Heath uses a half wavelength microstrip resonator, which is
tightly sandwiched between two sheets of sample test material.
These sheets of sample material are clamped in a special fixture.
The microstrip resonator is loosely capacitively coupled to
the microstrip feed line, which passes near one end of the
resonator normal to the resonator length. The dielectric constant
is determined from the measurement of resonant frequency and
Q factor for the transmission between sensor"s two input and
output ports. As the special cutting and positioning of thin
sheets of the sample material is required; Heath"s method is
not in situ or non-destructive.
King relates to the microwave resonator reflection sensor for
complex permittivity measurement in situ. The microstrip
resonator is fed from the ground plane side through a slot.
Microwave power is coupled to the slot through a coaxial line
or a raicrostrip. The material under test is kept in contact
with the sensor. The resonant frequency and input power coupling
factor is measured at the resonant frequency. The real and
imaginary parts of permittivity (f "and £ ") or the conductivity
(s) are determined from the resonant frequency and coupling
coefficient data using approximate closed form expressions.
King uses bottom fed resonators which claims to be a major
modification but this leads to complicated assembly and unstable
mounting compared to the side-coupled resonator. The
approximation in the basic expression of capacitance of the
cross section of the sensor leads to the serious inaccuracies
in the results. The closed form expressions need use of standards
for calibration to evaluate constants. King depends upon
empirical or analytical calibration. Evaluation of constants
before the installation and commissioning of the sensor is
essential. The starting equation of effective capacitance of
King is based on the assumption that the fringing fields constant
is same for all thickness of sample. Our analysis (fig.12) shows
that the resonant frequency varies with the permittivity as
well as material thickness. King is limited to the measurement
of infinitely thick samples only. The empirical calibration
techniques of King leads to errors if the thickness of the sample
is different than the calibration standard. King claims the
in situ sensor but it is not possible to perform in situ
calibrations in most situations, as the chamber cannot be filled
with the calibration liquid or solid. King leads to errors in
the calculated and true data due to calibrations using standards.
The same; is true for the analytical calibrations as the actual
surface itregularities and air gaps between resonator and the
solid sample contribute to the errors in measurements. It is
essential to validate analytical technique with the standard
data. Dispersion in microstrip with dielectric overlay also
plays an important part in errors. None of the empirical
calibration techniques using closed form expressions account
for dispersion. The shifts in the resonant frequency can be
larger than 1 GHz at the material permittivities of 10(fig.13).
Hence dispersion affects accuracy at first decimal place of
permittivity.
Both Flemming and Heath involve transmission from one input
port to an output port. Both ports are loosely and capacitively
coupled to the intervening resonator by capacitive coupling.
King relates only to the critically coupled reflection one port
sensor. King relates to the samples of very large size compared
to the sensor. Gerhard relates to the measurement real part
of the dielectric constant only. The samples under consideration
are thin sheets of dielectric materials.
Gabelich"s measures dielectric homogeneity at 100 KHz to 2MHz
for the use of dielectric substrates for CTS-ESA radar antennas
on Barium STrontium Titanate (BST). The C band or microwave
permittivity is co-related to low frequency permittivity even
though it is not accurate enough. Gabelich"s measures only real
part of permittivity.
US patent no 5686841 Nov 11,1997, Stolarczyk et. al teach the
use of patch antenna to detect presence of ice, water and/or
antifreeze mixtures on wings of the aircraft or roads. A single
frequency is fed to the antenna which is one of the arms of
the bridge circuit. This frequency is varied until admittance
of the antenna approaches zero. The object of the Stolarczyk"s
invention is not to accurately determine complex or real
permittivity but to only detect formation of ice. The frequency
resolution of the frequency variation is very low, of the order
of 2.4MHz.
OBJECTS OF THE INVENTION
A primary object of this invention is to propose a process and
apparatus for the measurement and monitoring of complex
permittivity and conductivity of materials in situ which is
accurate.
Another object of this invention is to propose a process and
apparatus for the measurement and monitoring of complex
permittivity and conductivity of materials in situ using
automatic scalar or vector network analyzers or swept frequency
generators and peak detectors that perform fast and accurate
frequency and amptitude measurements.
Still another object of this invention is to propose a process
and apparatus for the measurement and monitoring of complex
permittivity and conductivity of materials in situ employing
online numerical analysis software performing numerous iterations
to arrive at convergence within few seconds with required
accuracy like ± 0.1 or t 0.01 in case of £ and ± 0.0001 or ±
0.0005 in case of e .
Yet another object of this invention is to propose a process
and apparatus for the measurement and monitoring of complex
permittivity and conductivity of materials in situ and wherein
the determination of real and imaginary parts of permittivity
takes place in a relatively short period.
A further object of this invention is to propose a process and
apparatus for the measurement and monitoring of complex
permittivity and conductivity of materials in situ and wherein
the permittivity measurement does not depend on the first order
• approximations and simplistic closed form expressions involving
unkown constants.
A still further object of this invention is to propose a process
and apparatus for the measurement and monitoring of complex
permittivity and conductivity of materials in situ and used
for high frequency circuits boards, various bulk polymers and
semiconductor materials.
Yet a further object of this invention is to propose a process
and apparatus for the measurement and monitoring of complex
permittivity and conductivity of materials in situ and wherein
transmission type resonators may be used for samples of smaller
size than the resonator.
DESCRIPTION OF THE INVENTION:
The invention provides a device and process for measuring and
monitoring complex permittivity of materials for quality control,
in situ and in the materials measurement laboratory. Material
under test is kept as an overlay on microstrip, asymmetric
stripline, co-planar waveguide, patch or a disc resonator. The
resonator has its resonant frequency in the range of 0.5 to
20 GHz. The material is placed in contact with the top conductors
of the circuits or with a finite air gap above the top conductor.
The ground plane at the top may or may not be used. Fringing
field from the top surface and the edges of the resonator passes
through the material under test kept as an overlay dielectric.
As the fields above the substrate pass through the material
under test the effective permittivity of the resonator increases.
The Q factor {Q-ß/2a) of the resonator changes due to change
in the propagation constant (ß) and attenuation constant (a).
Increase in the effective permittivity of a microstrip, asymmetic
stripline, coplanar waveguide resonator, rejection filter, patch
or a disc causes decrease in the resonant frequency of the
resonator. Q factor of the resonator decreases as the attenuation
due to overlay adds to the total losses.
The invention envisages the use of transmission as well as
reflection type resonators. The resonators are coupled to the
source of microwave power using direct or gap coupling
(capacitively or inductively) from the side of the microstrip
conductor and not from the ground plane side. The measurements
may be one port or two port depending upon the dimensions of
the material under test. If a swept frequency source is used
then a resonant dip may be observed in the reflection or
transmission mode with the available instrument accuracy. Q
factor is directly measured using half power frequencies and
the resonant frequency. The unloaded Q measurement is preferred
for the accurate measurement C " or s If loaded Q is measured
then it is necessary to calculate unloaded Q from loaded Q
factor. The resonant or half power frequencies may be
automatically of manually measured and fed to the computer using
data acquisition system and/or frequency tracking device. The
dedicated computer program calculates real and imaginary parts
of the complex permittivity or conductivity of the material
under test. The program is based on the numerical analysis of
a microstrip embedded in multiple dielectric layers, the material
under test being the layer of unknown permittivity.
DESCRIPTION OF INVENTION WITH REFERENCE TO ACCOMPANYIG DRAWINGS
The invention will be further described with the help of
accompanying drawings, in which
Fig.1 shows a block diagram of an instrument using scalar or
vector Network analyzer
Fig.2 shows a diagram of an instrument using power meter or
ratio meter
Fig.3 shows a block diagram of an instrument with the reflection
type sensor and the test specimen
Fig.4 shows a schematic diagram of a direct coupled, reflection
type sensor (microstrip atch antenna) and the test specimen
Fig.5 shows a schematic diagram of a direct coupled, reflection
type microstrip sensor (quarter or half wavelength) and the
test specimen
Fig.6 shows a schematic diagram of a gap coupled, transmission
and/or reflection type sensor (quarter or half wavelength) and
the test specimen
Fig.7. shows a cross sectional diagram of a transmission and/or
reflection type microstrip sensor and the test specimen of finite
height
Fig.8 shows a cross sectional diagram of a transmission and/or
reflection type microstrip sensor and bulk test specimen of
with a very large dimensions
Fig.9 shows a cross sectional diagram of a transmission and/or
reflection type asymmetric stripline sensor and test specimen
of finite height
Fig.10 shows a schematic diagram of a direct coupled, reflection
type coplanar waveguide sensor (quarter or half wavelength)
and the test specimen
Fig.11 shows a schematic diagram of a gap coupled, transmission
type microstrip ring resonator sensor (one wavelength) and the
test specimen
With reference to the drawings, Fig.1 and 2 are schematic
diagrams showning an arrangement of the apparatus for the use
in this- invention. Fig.1 shows an instrument for the
determination of complex permittivity of materials comprising:
I. Automated scalar or vector network analyzer; II. reflection
or transmission type microwave sensors of any type and as
shown in Fig.3,4,5,6,7,8,9,10,11; III. A computer with IEEE
GPIB or any other standard interface; IV. Data acquisition and
postprocessing numerical analysis software for the determination
of complex permittivity loaded on the computer.
Fig. 2 shows schamatic diagram of the instrument using I. sweep
generator; II. reflectometer bridge or directional coupler;
III. power meter or VSWR meter; IV. Computer with IEEE GPIB
or any other standard interface; 5. reflection or transmission
type microwave sensors 2 or 7 of any type shown in
fig.3,4,5,6,7,8,9,10,.11. The network analyzer has a built in
synthesized sweep generator which generates swept frequency
output with the required frequency span. The frequency resolution]
of the sweep generator can be as high as 1 Hz. The output power
level may be adjusted to the required value. The swept microwave
power output of the sweep generator is coupled to the sensor
circuit via a special purpose test fixture and a coaxial cable.
If the sensor in the test fixture is of reflection type then
a directional coupler or a reflectometer bridge is used to
isolate reflected power and then it is coupled to the detector
port. The reference signal is being fed externally in case of
a scalar network analyzer. The network analyzer calculates ratio
of reflection and/or transmitted parameters to the input power
to the sensor for the range of swept frequencies. The reasonant
frequency is displayed on the screen as a sharp peak is observed
due to the storage of power in the resonator. The half power
frequencies are observed on the screen with the help of automatic
3 dB search or manually. According to the block diagram of Fig.2,
sweep generator generates swept signal and is fed to the sensor
2 or 7 through the reflectometer bridge. The test specimen 4
of unkown permittivity is kept as ^n overlay on the reflection
sensor. Microwave power is coupled to the reflection sensor
2 or 7 through a coaxial cable using standard coaxial to
microstrip transition like SMA connector. The reflectometer
separates reflected signal from the outgoing signal and is
measured by the power meter. The transmitted signal can be
measured by the power meter directly. The resonance is detected
by the displayed power output reading of the sensor at the
particular frequency. The frequency resolution of the instrument
and process is the resolution of the sweep generator which can,
be as high as 1 IIz.
Fig.3 shows a block diagram with an automated scalar or vector
network analyzer; coaxial cable 1, reflection type microwave
sensor 2, test specimen 4 of unknown permittivity 6 kept as
an overlay on the reflection sensor.
Fig.4 shows a schematic diagram of a microstrip patch antenna
16 as a reflection sensor 2 delineated on substrate 3 of known
permittivity £ 1, with the feed line 5 and the test material
4 kept as an overlay.
Fig.5 shows a schematic diagram of a microstrip quarter or
half wavelength resonator as a reflection sensor 2 delineated
on substrate 3 of known permittivity 61, with the feed line
5 and the test material 4 of unknown permittivity 6(e ) kept
as an overlay.
Fig.6 shows a schematic diagram of a gap coupled half wavelength
microstrip resonator as a transmission sensor 7 with the feed
line 5 and the test material 4 of unknown permittivity £ kept
as an overlay.
Fig. 7 shows a cross sectional diagram of a raicrostrip sensor
conductor 10, ground plane 9, substrate 8 and the test specimen
4 of finite height and unknown permittivity 6(£) kept as an
overlay.
Fig.8 shows a cross sectional diagram of a microstrip sensor
conductor 10, ground plane 9, substrate 8 and the test specimen
4 of finite height and unknown permittivity 6(£ ) kept as an
overlay. The bulk test specimen 4 is shown to be of very large
dimensions.
Fig.9 shows a cross sectional diagram of a transmission and/or
reflection type asymmetric stripline sensor 11, with a microstrip
sensor conductor 10, ground plane 9, substrate 8 and the test
specimen 4 of finite height and unknown permittivity 6(£) kept
as an overlay and a top ground plane 12.
Fig.10 shows a schematic diagram of a direct coupled, reflection
type coplanar waveguide sensor 15(quarter or half wavelength)
and the test specimen 4 unknown permittivity 6(C) kept as an
overlay.
Fig.11 shows a schematic diagram of a gap coupled, transmission
type microstrip ring resonator sensor 14(one wavelength) and
the test specimen 4 of smaller dimensions than the resonator
length having unknown permittivity 6(£) kept as an overlay at
the 90 orientation with respect to the feed line 5.
Fig.12 shows results of the numerical software of the present
invention simulating a reflection or transmission type microstrip
sensor. The graph shows variation of effective permittivity
[ with respect to cover permittivity and test material thickness
when the test material completely overlaps the sensor. This
graph indicates the difference between other inventions of using
microstrip resonator sensors kept in the vicinity of test
material. This invention does not use any approximate closed
form expressions for the calibration of sensor but uses on-line
numerical analysis which does not require use of known standards
or empirical calibrations (like Flemming et. al. US patent
no.4,829.233 or King 5,334,941); but uses on-line or off-line
computer software.
test. A dedicated computer program computes complex permittivity using
electromagnetic numerical analysis software analyzing resonator embedded(fig 7,8)
in multiple dielectric layers. The program takes less than three seconds on the IBM
compatible computer with Pentium 350 MHz processor and three minutes on 80386
processor. The user can choose the required accuracy.
The material under test,4 for which complex permittivity,6 is to be measured is kept
in direct contact of the resonator or keeping a gap of few microns from the
resonator. A top ground plane, 12 is optional. The computer program needs to be fed
the information on the type of resonator configuration as well as presence of top
ground plane and thickness and length of the material under test. the test set up
needs to be calibrated for acceptable connector assembly. The resonator is tested
without the presence of material under test initially. The resonant frequency and half
power frequency are measured and fed to the program. The sample or material under
test,4 is then placed over the resonator in the required orientation and the specified
position. The sensor is placed in the reaction chamber or a drier or in the moving
belt in case of flowing material without disturbing the connector assembly. The
presence of dielectric material in the vicinity of the resonator shifts frequency of
resonance due to the increase in the effective permittivity, eeff of the resonator.
Where subscripts * O and "s" stand for open and with loaded sample.
At resonance electrical length of a microstrip resonator is an integral
multiple of half wavelengths. The real part of effective permittivity eeff of an open
resonator is determined by the software program by feeding width of the top
conductor, substrate permittivity, substrate loss tangent and substrate permittivity. It
is necessary to know these values most accurately as the errors and uncertainties in
these values will reflect on the resultant values of permittivities of specimens kept
as overlays. Hence utmost care is required in designing and fabricating the test
vehicle. The eeff, thus determined is numerically postprocessed by the program to
determine specimen real part of the permittivity £r the required accuracy may be
fed to the interactive program at the maximum of ±0.01.
The Quality factor, Q of the resonator changes due to the additional
dielectric and conductor losses due to the overlay material. Our numerical analysis
shows increase in the total toss due to dielectric covert fig. 15). The unloaded Q
factor of a resonator is given by the standard relation.
The software also calculates conductor loss for the microstrip with cover specimen.
This is not same as an open microstrip conductor loss[7]. The program evaluates the
dissipation factor of cover specimen from the given data using electromagnetic
numerical analysis. The radiation loss can be neglected if desired.
Neglecting radiation losses the program calculates contribution of cover dielectric to
the dielectric loss and hence gives the value of dissipation factor tan S of the
sample.

where Qf= Quality factor due to conductor losses
Q4= Quality factor due to dielectric losses
Qd= Quality factor due to radiation losses
Let Qtfopen} - Total Quality factor of an open microstrip resonator
at(cover) = Total Quality factor of a covered microstrip resonator
a ~ Total attenuation per unit length of an open microstrip resonator
at(cover) - Total attenuation per unit length of a covered microstrip resonator

The numerical analysis indicates conductor loss ac(cover) as well as ad of a
microstrip with dielectric cover is larger than the open microstrip. For low
permittivity and lossy materials the increase in the conductor loss may be neglected
Neglecting radiation losses.

where q,= filling fraction due to substrate
e, = real part of permittivity of substrate
q2,= filling fraction due to dielectric cover
e2= real part of permittivity of the cover

It can be noticed that determination of e" or tan 6 requires a value of e" of the test
material. King(US patent no. 5334941) neglects dependence of e" on the effective
capacitance and treats effective capacitance as a constant, which is certainly not the
case. Therefore determination of e" has inherent inaccuracy in King"s method.
This invention actually used a highly accurate value of e" in the
determination of e" along with the numerically calculated conductor and dielectric
losses.

From equations (9) and (11)

where the program uses the value of e2 obtained numerically beforehand and

In case materials with very low values of tand increase in the conductor loss due to
increased effective permittivity needs to be subtracted from the total loss. The
computer program takes dare of it from the determined value of tan5. Hence the
process is applicable to materials with high and low loss dielectrics including
materials used for high frequency applications in microwave region.
Measurement of material samples that are smaller in dimensions
than that of the resonator:
The invention provides a process of measurement of complex permittivity of
samples that are smaller in length(fig.6) and breadth(fig. 11) than that of the
resonator. The examples of such samples are single grain of wheat, coffee, rise,
GaAs, diamond and other precious stones, various types of medicine capsules etc.
The invention can be used for studying sample to sample variation in the complex
permittivity of objects of the dimensions of few millimeters. The software will ask
for the dimensions of the material sample under test and will follow the required
subroutine.
For a half wave resonator

where subscripts 1 and 2 stand for different materials overlaying the resonator.
If the sample is partially covering the resonator in the region 2 then eeff, assumes the
value of effective permittivity for the open microstrip and /, is the length of the open
region of the resonator. eeff is the unknown value of effective permittivity of the
overlaid microstrip at the frequency of operation. Equation holds for both real and
imaginary parts of eeff The effect of dispersion needs to be taken into account. In the
present invention software is taking care of dispersion. The unknown effective
permittivity is determined using the equation (15) by the software
It is possible to use this technique at the
manufacturing site to monitor chemical reactions involving
insulating or low conductivity materials and quality of materials
like poly tetra fluro ethylene (PTFE) and other polymer, rubbers
and foams. The instrument and the process may be used at the
various stages of manufacturing or curing or processing of
polymer, organic, food or agricultural products to ensure the
final quality. The process and instrument may be used to detect
voids, porosity, cracks, and non-uniformity of permittivity
or density of the material.
The microstip resonator used as a test vehicle may
be pre-calibrated before the measurment starts. It may also
be possible to use calibration standard overlays to define system
uncertainties. After establishing acceptable connector assembly
the connector and fixture repeatability does not affect sample
to sample measurements. This is due to the fact that input and
output cables and connections to the resonator and/or test
vehicle are tested before the sample is loaded and are unaltered
thereafter during measurment. It is not necessary to connect
the disconnect the test vehicle if next sample is to be measured.
This is a significant advantage over the existing test methods
for high frequency circuit boards and materials like IPC-TM-
650, no. 2.5.5.5.1, and the document of International Packaging
Commission.
The test vehicle design may include care for avoiding
loading error so that loading error is avoided with confidence.
This is a distinct advantage as the loading error uncertainties
remain to be tackled at the time of measurments in method IPC-
TM-650, no. 2.5.5.5.1. The loading time for the specimen may
be of a few seconds. The response of a network analyzer is within
fraction of a second. Determination of permittivity with the
computer takes few seconds. Therefore the measurments may be
very fast for multiple samples. The accepted methods require
either fabrication of microstrip resonators on the sample under
test or need a complicated assembly clamping which may take
longer for each sample measurment.
The present invention exploits maximum resolution
of frequency source and detector of Network analyzers which
is quoted to be 1Hz by Hewlett Packard for its vector Network
analyzers. Patch antenna of either rectangular or disc shaped
is used to determine real dielectric constant with the accuracy
of +0.015 and tan to the accuracy of +0.0001 or more. Single
antenna or any other type of resonator is used to measure complex
permittivity with the help of online numerical analysis program.
There are many differences and uses of the present
invention in comparison with the inventions of Health, Flemming,
Gerhard, Gabelich and King. In particular variety of sample
dimensions can be accommodated from 3 mm(fig.6,11)e.g. wheat
or rice grain or pallet or tablet; to very large dimensions
in length and breadth (fig. 4,5,8,10). Depth of the sample may
be as small as 0.1mm (fig. 6,7,8) to few meters depth
(Fig.4,5,8,10,11). The present invention can also be used for
the measurment of complex permittivity (fig.7,8,10) and
dielectric homogeneity in the sheets of dielectric materials.
The test material needs to be moved relative to the sensor or
multiple sensors may be employed in the production process.
The present invention uses on-line numerical analysis software
which has been validated for variety of materials of known
WE CLAIM1:
. An instrument for the measurement of complex permitivity
of dielectric materials in solid, liquid and semisolid state
comprising:
(a) a microwave resonator selected from the group of
transmission and reflection resonators, said microwave resonator
having a resonator surface;
(b) a microwave sweep oscillator, the output of which is
coupled to the microwave resonator;
(c) a detector associated with the microwave resonator for
detecting a frequency shift and a Q factor of the microwave
resonator;
(d) means for coupling power to and from the microwave
resonator;
(e) means for measuring the power supplied to and received
from the microwave resonator;
(f) a computer interfaced with a system with components
including the microwave sweep oscillator, the microwave
resonator, the detector and the means for measuring the power;
(g) electromagnetic software for the analysis of complex
permitivity of the dielectric materials; and
(h) an interfacing software for communication between
components of the system and the computer.
2. The instruments for the measurement of complex permitivity
of dielectric materials as claimed in claim 1 wherein the
reflection microwave resonator is selected from the group
consisting of :
(a) a microstrip ring resonator,
(b) a microstrip half wavelength resonator;
(c) a microstrip quarter wavelength resonator,
(d) a microstrip patch resonator;
(e) a coplanar wave-guide half wavelength resonator;
(f) a coplanar wave-guide quarter wavelength resonator;
(g) an asymmetric stripline half wavelength resonator;
and
(h) an asymmetric stripline quarter wavelength resonator.
3. The instrument for the measurement of complex permitivity
of dielectric materials as claimed in claim 1 wherein the trans-
mission type of microwave resonator is selected from the group
consisting of:
(a) a microstrip ring resonator;
(b) a microstrip half wavelength resonator;
(c) a coplanar wave-guide half wavelength resonator; and
(d) an asymmetric stripline half wavelength resonator.
4. The instrument for the measurement of complex permitivity
of dielectric materials as claimed in claim 1 wherein the micro-
wave resonator is a non-contact sensor and is attached with a
device for loading and unloading the dielectric material under
test with a known separation from the resonator surface.
5. The instrument for the measurement of complex permitivity
dielectric materials as claimed in claim 1 wherein the
resonator surface is coated with a protective coating selected
from the group consisting of a thin film, a thick film and a die-
electric sheet.
6. A process for the measurement of complex permitivity of
dielectric materials comprising:
pre-calibrating a measurement system;
connecting a microwave resonator to the measurement
system;
recording the charcteristic response of the microwave
resonator;
determining the resonant frequency, loaded and unloaded
quality factor of the microwave resonator;
determining an effective permitivity of the open microwave
resonator, eeff0 by using electromagnetic software;
placing a dielectric material to be tested over the
microwave resonator;
recording the characteristic response of the microwave
resonator with the dielectric material under test as an overlay
on the microwave resonator;
determining the resonant frequency, loaded and unloaded
quality factor of the resonator with the dielectric overlay; and
determining an effective permitivity of the microwave
resonator with the dielectric overlay, eeffs using the equation
and
determining real and imaginary parts of permitivity ( E" and
E") of the dielectric overlay using the electromagnetic software.
7. The process for the measurement of complex permitivity of
dielectric materials as claimed in claim 6 further comprising the
step of:
selecting a reflection resonator, as the microwave
resonator, from the group consisting of:
(a) a microstrip ring resonator;
(b> a microstrip half wavelength resonator?
(c) a microstrip quarter wavelength resonator;
(d) a microstrip patch resonator;
(e) a coplanar wave-guide half wavelength resonator
(f) a coplanar wave-guide quarter wavelength resonator;
(g) an asymmetric stripline half wavelength resonator;
and
(h) an asymmetric stripline quarter wavelength reasonator;
8. The process for the measurement of complex permitivity of
dielectric materials as claimed in claim 6 further comprising the
step of:
selecting a transmission type resonator, as the microwave
resonator, from the group consisting of:
(a) a microstrip ring resonator;
(b) a microstrip half wavelength resonator;
(c) a coplanar wave-guide half wavelength resonator;
and
(d) an asymmetric stripline half wavelength resonator.
9. The process for the measurement of complex permitivity of
dielectric materials as claimed in claim 6 further comprising the
steps of:
loading the dielectric material under test with a known
separation from the resonator, said separation being provided
with a protective dielectric coating.
10. The process for the measurement of complex permitivity of
dielectric materials as claimed in claim 6 further comprising the
step of:
automatically measuring the resonant frequency and Q
factor of the microwave resonator with an on-line computing
device.
11. A process for the measurement of complex permitivity of
dielectric materials as claimed in claim 6 wherein the size of
the dielectric material under test is selected from the group
consisting of s
(a) smaller than the microwave resonator;
(b) larger than the microwave resonator;
(c) of the size of the microwave resonator.
An instrument for the measurement of complex permitivity
of dielectric materials in solid, liquid and semisolid state
comprising:(a) a microwave resonator selected from the group of
transmission and reflection resonators) said microwave resonator
having a resonator surface; (b) a microwave sweep oscillator, the
output of which is coupled to the microwave resonator; (c) a
detector associated with the microwave resonator for detecting a
frequency shift and a Q factor of the microwave resonator;(d)
means for coupling power to and from the microwave resonator;
(e) means for measuring the power supplied to and received from
the microwave resonator; (f) a computer interfaced with a system
with components including the microwave sweep oscillator, the
microwave resonator, the detector and the means for measuring the
power; (g) electromagnetic software for the analysis of complex
permitivity of the dielectric materials; and (h) an interfacing
software for communication between components of the system
and the computer.

Documents:

540-cal-1999-granted-abstract.pdf

540-cal-1999-granted-claims.pdf

540-cal-1999-granted-correspondence.pdf

540-cal-1999-granted-description (complete).pdf

540-cal-1999-granted-drawings.pdf

540-cal-1999-granted-examination report.pdf

540-cal-1999-granted-form 1.pdf

540-cal-1999-granted-form 18.pdf

540-cal-1999-granted-form 2.pdf

540-cal-1999-granted-form 26.pdf

540-cal-1999-granted-form 3.pdf

540-cal-1999-granted-letter patent.pdf

540-cal-1999-granted-reply to examination report.pdf

540-cal-1999-granted-specification.pdf


Patent Number 214266
Indian Patent Application Number 540/CAL/1999
PG Journal Number 06/2008
Publication Date 08-Feb-2008
Grant Date 07-Feb-2008
Date of Filing 11-Jun-1999
Name of Patentee KALPANA JOSHI
Applicant Address 5,BALLYGUNGE CIRCULAR ROAD, CALCUTTA-700019. WEST BENGAL.
Inventors:
# Inventor's Name Inventor's Address
1 KALPANA GHOSH 5,BALLYGUNGE CIRCULAR ROAD, CALCUTTA-700019. WEST BENGAL.
PCT International Classification Number G01N22/04,22/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA