Surendran,K P; Bijumon, P V; Mohanan, P; Sebastian,M T(Department of Electronics, April 14, 2005)
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Abstract:
The MgAl2O4 ceramics were prepared by the conventional
solid-state ceramic route and the dielectric properties
studied in the microwave frequency region (3–13 GHz).
The phase purity and crystal structure were identified using
the X-ray diffraction technique. The MgAl2O4 spinel ceramics
show interesting microwave dielectric properties (εr = 8.75,
Qux f = 68 900 GHz (loss tangent = 0.00017 at 12.3 GHz),
τf =−75 ppm/◦C). The MgAl2O4 has high negative τf, which
precludes its immediate use in practical applications. Hence
the microwave dielectric properties of MgAl2O4 spinels were
tailored by adding different mole fractions of TiO2. The
εr and Q factor of the mixed phases were increased with
the molar addition of TiO2 into the spinel to form mixtures
based on (1−x)MgAl2O4-xTiO2 (x = 0.0−1.0). For x = 0.25 in (1−x)MgAl2O4-xTiO2, the microwave quality factor
reaches a maximum value of Qux f = 105 400 GHz (loss tangent
= 0.00007 at 7.5 GHz) where εr and τf are 11.035 and
−12 ppm/◦C, respectively. The microwave dielectric properties
of the newly developed 0.75MgAl2O4-0.25TiO2 dielectric is
superior to several commercially available low loss dielectric
substrates.
An asymmetric coplanar strip (ACS) fed dual band F-shaped antenna covering the 2.4/5.2 GHz WLAN bands is presented. The optimized dimensions of the proposed uniplanar antenna are 21 mm × 19 mm when printed on a substrate of dielectric constant 4.4 and height 1.6 mm. The dual band nature of the antenna is brought about by the various current paths in the F-shaped structure and the ground plane. The antenna exhibits nearly omnidirectional radiation characteristics and moderate gain in both the operating bands. Details of the antenna design, simulation, and experimental results are presented and discussed.
Bindu, G; Anil, Lonappan; Vinu, Thomas; Aanandan,C K; Mathew, K T(Progress In Electromagnetics Research, 2006)
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Abstract:
Active microwave imaging is explored as an imaging
modality for early detection of breast cancer. When exposed to
microwaves, breast tumor exhibits electrical properties that are
significantly different from that of healthy breast tissues. The
two approaches of active microwave imaging — confocal microwave
technique with measured reflected signals and microwave tomographic
imaging with measured scattered signals are addressed here. Normal
and malignant breast tissue samples of same person are subjected to
study within 30 minutes of mastectomy. Corn syrup is used as coupling
medium, as its dielectric parameters show good match with that of
the normal breast tissue samples. As bandwidth of the transmitter is
an important aspect in the time domain confocal microwave imaging
approach, wideband bowtie antenna having 2:1 VSWR bandwidth
of 46% is designed for the transmission and reception of microwave
signals. Same antenna is used for microwave tomographic imaging too
at the frequency of 3000 MHz. Experimentally obtained time domain
results are substantiated by finite difference time domain (FDTD)
analysis. 2-D tomographic images are reconstructed with the collected
scattered data using distorted Born iterative method. Variations of
dielectric permittivity in breast samples are distinguishable from the
obtained permittivity profiles.
Botha, E C; Odendaal, J W; Geggus, K M(Microwave and Optical Technology Letters, February 20, 1998)
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Abstract:
Compact-range radar backscatter measurements are taken
of aircraft scale models. In addition, computer software is used to predict
the RCS of the aircraft. Synthetic down-range profiles formed from the
two sources of backscatter data are compared and visualized in an
innovative manner. Similar discrimination rates between the two aircraft
are obtained on data from both source
Manju,Paulson; Sona,Kundukulam O; Aanandan,C K; Mohanan, P(Microwave and Optical Technology Letters, January 20, 2002)
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Abstract:
A dual-port dual-polarized compact microstrip antenna
for avoiding cross coupling between the two frequency bands is proposed
and analyzed. This antenna offers channel isolation better than 25 dB,
and is more compact compared to a conventional rectangular patch.
Analytical equations for calculating the resonant frequencies at both
ports are also presented. The theoretical calculations are verified using
experimental results
Donghyun,Kim; Sangseol,Lee(Microwave and Optical Technology Letters, July 20, 2002)
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Abstract:
Most adaptive linearization circuits for the nonlinear amplifier
have a feedback loop that returns the output signal oj'tne eunplifier
to the lineurizer. The loop delay of the linearizer most be controlled
precisely so that the convergence of the linearizer should be assured lot
this Letter a delay control circuit is presented. It is a delay lock loop
(ULL) with it modified early-lute gate and can he easily applied to a
DSP implementation. The proposed DLL circuit is applied to an adaptive
linearizer with the use of a polynomial predistorter, and the simulalion
for a 16-QAM signal is performed. The simulation results show that
the proposed DLL eliminates the delay between the reference input signal
and the delayed feedback signal of the linearizing circuit perfectly,
so that the predistorter polynomial coefficients converge into the optimum
value and a high degree of linearization is achieved
A novel optical add-drop multiplexer (OADM) based on
the Mach-Zelauler interferometer (MZI) and the fiber Bragg grating
(FBG) is proposed for the first tittle to the authors ' knowledge. In the
structure, the Mach-Zehnder interferometer acts as an optical switch.
The principle of the OADM is analyzed in this paper. The OADM can
add/drop one of the multi-input channels or pass the channel directly by
adjusting the difference of the two arms of the interferometer. The channel
isolation is more than 20 dB
Aanandan,C K; K G Nair; Mohanan, P; Jacob,George(Department of Electronics, November , 1998)
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Abstract:
A new compact microstrip antenna element is analyzed.
The analysis can accurately predict the resonant frequency,
input impedance, and radiation patterns. The predicted results
are compared with experimental results and excellent agreement
is observed . These antenna elements are more suitable in applications
where limited antenna real estate is available
Jacob,George; Aanandan,C K; Mohanan, P; K G Nair(IEEE Journals/ Transactions (USA), 1998)
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Abstract:
A new compact micro strip antenna element is analyzed.
The analysis can accurately predict the resonant frequency,
input impedance, and radiation patterns. The predicted results
are compared with experimental results and excellent agreement
is observed . These antenna elements are more suitable in applications
where limited antenna real estate is available
Mohanan, P; K G Nair; Aanandan,C K; Supriyo,Dey(Department of Electronics, February 3, 1994)
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Abstract:
The closed form expression for the radiated power of a half-wave
microstrip patch is modified to calculate the impedance
bandwidth of a printed dipole. Analyses of cavity backed flared
and end-loaded printed dipoles are presented
Huo,Y; Taylor,G W(Microwave and Optical Technology Letters, May 20, 2003)
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Abstract:
The operation of a previously proposed terahertz (THZ)
detector is formulated in detail. The detector is based on the hot-electron
effect of the 2D electron gas (2DEG) in the quantum well (QW) of
a GaAs/AIGaAs heterostructure. The interaction between the THz radiation
and the 2DEG, the current enhancement due to hot -electron effect, and
the noise performance of the detector are analyzed
Sona,Kundukulam O; Manju,Paulson; Aanandan,C K; Mohanan, P(Microwave Engineering Group,Department of Electronics, April 20, 2002)
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Abstract:
Design equations are presented for calculating the resonance frequencies for a
compact dual frequency arrow-shaped microstrip antenna. This provides a fast and simple
way to predict the resonant frequencies of the antenna. The antenna is also analyzed using the
IE3D simulation package. The theoretical predictions are found to be very close to the
IE3D results and thus establish the validity of the design formulae
Choudhury, P K; Roger, Lessard S(Microwave and Optical Technology Letters, January 20, 2002)
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Abstract:
An attempt is made to determine the relative power
distribution in a step-index parabolic cylindrical waveguide (PCW) with
high deformation across the direction of propagation. The guide is
assumed to be made of silica. The scalar field approximation is employed
for the analysis under which a vanishing refractive-index (RI) difference
in the waveguide materials is considered. Further, no approximation for
folds- is used in the analytical treatment. Due to the geometry of such
waceguides, PCWs lose the well-defined modal discreteness, and a kind
of mode bunching is observed instead, which becomes much more
prominent in PCWs with high bends. However, with the increase in
cross-sectional size, the mode-bunching tendency is slightly reduced. The
general expressions for power in the guiding and nonguiding sections are
obtained, and the fractional power patterns in all of the sections are
presented for PCWs of various cross-sectional dimensions. It is observed
that the confinement of power in the core section is increased for PCWs
of larger cross-sectional size. Moreover, a fairly uniform distribution of
power is seen over the modes having intermediate values of propagation
constants
Tennant,A; Dawoud,M M; Anderson,A P(Department of Electronics, April 27, 1994)
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Abstract:
A genetic algorithm has been used for null steering in phased and
adaptive arrays . It has been shown that it is possible to steer the
array null s precisely to the required interference directions and to
achieve any prescribed null depths . A comparison with the results
obtained from the analytic solution shows the advantages of using
the genetic algorithm for null steering in linear array patterns
The characterization and grading of glioma tumors, via image derived features, for diagnosis, prognosis, and treatment response has been an active research area in medical image computing. This paper presents a novel method for automatic detection and classification of glioma from conventional T2 weighted MR images. Automatic detection of the tumor was established using newly developed method called Adaptive Gray level Algebraic set Segmentation Algorithm (AGASA).Statistical Features were extracted from the detected tumor texture using first order statistics and gray level co-occurrence matrix (GLCM) based second order statistical methods. Statistical significance of the features was determined by t-test and its corresponding p-value. A decision system was developed for the grade detection of glioma using these selected features and its p-value. The detection performance of the decision system was validated using the receiver operating characteristic (ROC) curve. The diagnosis and grading of glioma using this non-invasive method can contribute promising results in medical image computing
Description:
International Journal of Emerging Technologies in Computational and Applied Sciences, 7(1), December 2013-
February, 2014, pp. 08-14
Efficient optic disc segmentation is an important task in automated retinal screening. For the same reason optic disc detection is fundamental for medical references and is important for the retinal image analysis application. The most difficult problem of optic disc extraction is to locate the region of interest. Moreover it is a time consuming task. This paper tries to overcome this barrier by presenting an automated method for optic disc boundary extraction using Fuzzy C Means combined with thresholding. The discs determined by the new method agree relatively well with those determined by the experts. The present method has been validated on a data set of 110 colour fundus images from DRION database, and has obtained promising results. The performance of the system is evaluated using the difference in horizontal and vertical diameters of the obtained disc boundary and that of the ground truth obtained from two expert ophthalmologists. For the 25 test images selected from the 110 colour fundus images, the Pearson correlation of the ground truth diameters with the detected diameters by the new method are 0.946 and 0.958 and, 0.94 and 0.974 respectively. From the scatter plot, it is shown that the ground truth and detected diameters have a high positive correlation. This computerized analysis of optic disc is very useful for the diagnosis of retinal diseases
Description:
(IJACSA) International Journal of Advanced Computer Science and Applications,
Vol. 5, No. 7, 2014