Ceramics of composition BaO-Ln2O3-STiO2 have been prepared with four elements (Ln=La,Pr,Nd.Sm) by a conventional solid state ceramic preparation route and the dielectric properties measured in the microwave frequency range
The dielectric ceramics BaNd2Ti3Oto, BaNd2Ti4O12 and BaNd2Ti5O14 have been prepared by
Conventional solid state ceramic route. The sintered ceramic samples have been characterized by
X-ray diffraction and Scanning Electron Microscopy (SEM). The dielectric properties in the
microwave frequency range have been measured using conventional microwave dielectric
resonator methods. The BaNd2Ti1O10, BaN2Ti4O12 and BaNd2Ti5O14 have dielectric constants
(Er) ~ 60, 84 and 77 respectively. They have relatively high quality factors
Abdul Khalam,L; Sreemoolanadhan,H; Ratheesh, R; Mohanan, P; Sebastian,M T(ELSEVIER, 2003)
[+]
[-]
Abstract:
Microwave dielectric resonators (DRs) based on Ba(B1,2Nbi/2)03 [B' = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Yb, and In] complex
perovskites have been prepared by conventional solid state ceramic route. The dielectric properties (relative permittivity, Er; quality factor, Q;
and resonant frequency, rr) of the ceramics have been measured in the frequency range 4-6 GHz using resonance methods. The resonators
have relatively high dielectric constant in the range 36-45, high quality factor and small temperature variation of resonant frequency. The
dielectric properties are found to depend on the tolerance factor (t), ionic radius (r), and lattice parameter (ap)
Mailadil,Sebastian T; Sam,Solomon; Ravindran,Ratheesh(Regional Research Laboratory, April , 1999)
[+]
[-]
Abstract:
Microwave ceramic dielectric resonators (DRs) based on RETiNbO6
(RE = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Y, and Yb)
have been prepared using the conventional solid -state ceramic
route. The DR samples are characterized using XRD and SEM
methods. The microwave dielectric properties are measured
using resonant methods and a net work analyzer . The ceramics
based on Ce, Pr, Nd, and Sin have dielectric constants in the
range 32-54 and positive coefficient of thermal variation of
resonant frequency (r,). The ceramics based on Gd, Tb, Dy, Y.
and Yb have dielectric constants in the range 19-22 and
negative Tf
K G Nair ; P R S Pillai ; Vasudevan, K; Mathew, K T; Mohanan, P; Aanandan,C K(Cochin University of Science and Technology, November 29, 2008)
[+]
[-]
Abstract:
In this paper we have investigated the effect of cavity diameter and wall height on resonance and radiation characteristics of a circular microstrip patch antenna. Experiments were conducted using a fabricated prototype placed inside a cylindrical cavity. The results were compared and verified with simulated data obtained using an electromagnetic simulator. About 9.6 to 10.5 dBi peak gain was obtained from measured and simulated data
The propagation of pulse waves in coplanar waveguides
(CPWs) is investigated, and these CPWs are assumed to be fabricated
on a single -layer low- temperature co-fired ceramic (LTCC) substrate.
The input pulse wave can be a Gaussian pulse or a sinusoldally modulated
Gaussian pulse. Based on the standard Galerkin 's method in the
spectral domain, combined with fast Fourier transform (FFT), the pulse
waveform and delay in CPWs are demonstrated and compared for a second plate, oriented orthogonally to the primary planar element,
thus producing a crossed planar monopole (CPM), which is
simpler to produce and has lower cost than a conical monopole. In
this paper, further measurements have been made on this element
Bybi, P C; Jitha, B; Aanandan,C K; Vasudevan, K; Mohanan, P; Gijo,Augustin(Antennas and Wireless Propagation Letters, IEEE, 2008)
[+]
[-]
Abstract:
A compact, planar, wideband antenna designed by modifying the coplanar waveguide is presented in this letter. The proposed antenna finds a wide range of applications including advanced wireless systems (AWS), DCS-1800, DCS-1900/PCS/PHS, WiBro, BlueTooth/WLAN/WiBree/ZigBee, DMB, Global Star Satellite Phones, and digital cordless phones. Wide bandwidth > 75% centered at 2.50 GHz, quasi-omnidirectional radiation coverage along with moderate gain and efficiency are the salient features of the antenna. A prototype fabricated on a substrate with dielectric constant 4.4 and thickness 1.6 mm occupies an area of (31times 64) mm2. Details of antenna design and discussions on the effect of various antenna parameters on the radiation characteristics are presented.
Chandran,A R; Gopikrishna, M; Aanandan,C K; Mohanan, P; Vasudevan, K(IEEE, September 28, 2006)
[+]
[-]
Abstract:
Effective use of fractal-based metallo-dielectric structures for enhancing the radar cross-section (RCS) of dihedral corner reflectors is reported. RCS enhancement of about 30 dBsm is obtained for corner reflectors with corner angles other than 90deg. This may find application in remote sensing and synthetic aperture radar.
Gijo,Augustin; Shynu, S V; Mohanan, P; Aanandan,C K; Vasudevan, K(John Wiley & Sons, November , 2006)
[+]
[-]
Abstract:
A novel fixed frequency beam scanning microstrip leaky wave antenna is reported. The beam scanning at fixed frequency is achieved by reactive loading. Simulation and measured results shows frequency scanability of 80° as well as fixed frequency beam steering of 68° over the −10 dB impedance band of 4.56–5.06 GHz.
James, Kurian; Saseendran Pillai, P R(December 8, 2008)
[+]
[-]
Abstract:
This paper introduces a simple and efficient method
and its implementation in an FPGA for reducing the odometric
localization errors caused by over count readings of an
optical encoder based odometric system in a mobile robot
due to wheel-slippage and terrain irregularities. The detection
and correction is based on redundant encoder measurements.
The method suggested relies on the fact that the
wheel slippage or terrain irregularities cause more count
readings from the encoder than what corresponds to the
actual distance travelled by the vehicle. The standard quadrature
technique is used to obtain four counts in each encoder
period. In this work a three-wheeled mobile robot
vehicle with one driving-steering wheel and two-fixed rear
wheels in-axis, fitted with incremental optical encoders is
considered. The CORDIC algorithm has been used for the
computation of sine and cosine terms in the update equations.
The results presented demonstrate the effectiveness
of the technique
Description:
Journal of Automation, Mobile Robotics & Intelligent Systems VOLUME 3, No 3 2009
Shynu, S V; Gijo,Augustin; Aanandan,C K; Mohanan, P; Vasudevan, K(Microwave and Optical Technology Letters, February 4, 2005)
[+]
[-]
Abstract:
A novel reconfigurable, single feed, dual frequency, dualpolarized
operation of a hexagonal slot-loaded square mwrostrip antenna
is presented in this paper. A pin diode incorporated in the slot is
used to switch the two operating frequencies considerably, without significantly
affecting the radiation characteristics and gain. The proposed
antenna provides a size reduction up to 61% and 26% Jor the two resonating
frequencies, compared to standard rectangular patches. This design
also gives considerable bandwidth up to 3.3% and 4.27%, for the two
frequencies with a low operating frequency ratio
Mridula, S; Binu, Paul; Mohanan, P; Bijumon, P V; Sebastian,M T(URSI, October , 2005)
[+]
[-]
Abstract:
Experimental investigations on Microstrip line excited Dielectric Resonator Antenna configurations suitable for Mobile Communication applications are reported. High permittivity (εrd = 48) resonator samples with different aspect ratios are employed for the study. Theoretical analysis performed using FDTD method is also presented.
Suma,M N; Sreedevi, Menon K; Bijumon, P V; Sebastian,M T; Mohanan, P(Microwave and Optical Technology Letters, April 20, 2005)
[+]
[-]
Abstract:
In this paper, we present an effective excitation of a reelangular
dielectric resonator antennas (DRA) with a conductor-hacked
coplanar waveguide (CB-CPW). The radiation and resonance characteristics
are found to van,, depending on the orientation of the DR on
doe coplanar feed line. The effect of finite and infinite ground planes of
CB-CPIV on the radiation characteristics of the rectangular DRA is
studied. The orientation and position of the DR are optimized for maximum
gain and bandwidth. The optimized antenna ,geometry offers
--10.46 dBi gain and 7.5% bandwidth with low cross-polar radiation
characteristics
Paulson,M; Sona,Kundukulam O; Aanandan,C K; Mohanan, P(Department of Electronics, September , 2001)
[+]
[-]
Abstract:
The arrow shaped microstrip antenna, which produces
dual frequency dual polarisation operation with considera-ble size reduction compared to conventional patches has been
reported [I]. These antennas provide greater area reduction and
improved gain compared to drum shaped patches [2]. Prediction
of the resonance frequency of drum shaped patches [3] and circular
patches for broadband operation [4] are available in the literature.
In this Letter, we propose empirical formulas for calculating
the resonance frequencies of the arrow shaped microstrip antenna.
These antennas can be employed for obtaining dual frequency
with the same polarisation, bandwidth enhancement, circular
polarisation etc. by varying its different parameters or by introducing
slots. The proposed design equations provide an easier and
simple way of predicting the resonant frequencies of these patches.
A simple technique for calculating the resonance frequencies of a
compact arrow-shaped microstrip antenna is presented and discussed . The accuracy of the method is validated by experimental results
Sona,Kundukulam O; Paulson,M; Aanandan,C K; Mohanan, P; K G Nair(Department of Electronics, October , 2002)
[+]
[-]
Abstract:
A dual-port microstrip antenna with a crescent shaped
patch with excellent isolation betwecn the ports has been reportcd [I].
Since circular-sided geometries are inore compact than rectangular
oncs, thcy find morc applications in microstrip arrays. The crcscent
shaped antenna geometry [ I ] provides greater area rcductioii compared
to other circular sided patches for broadband operation [2]. In this
Lctter, formulac for calculating thc TM, I and TMZI mode resonant
frequencies of this microstrip antenna, obtained by modifying the
equations of a standard circular patch [3] are presentcd. Thcorctical
results are compared with experimental observations aid the validity
of the computation is established.
Chandran,A R; Gopikrishna, M; Aanandan,C K; Mohanan, P; Vasudevan, K(Progress In Electromagnetics Research, 2007)
[+]
[-]
Abstract:
The scattering behaviour of fractal based metallodielectric structures loaded over metallic targets of different shapes such as flat plate, cylinder and dihedral corner reflector are investigated for both TE and TM polarizations of the incident wave. Out of the various fractal structures studied,square Sierpinski carpet structure is found to give backscattering reduction for an appreciable range of frequencies. The frequency of minimum backscattering depends on the geometry of the structure as well as on the thickness of the substrate. This structure when loaded over a dihedral corner reflector is showing an enhancement in RCS for corner angles other than 90◦.
Tessamma, Thomas; Ananda Resmi, S(Scientific Research Publishing, July 28, 2012)
[+]
[-]
Abstract:
This work presents an efficient method for volume rendering of glioma tumors from segmented 2D MRI Datasets with user interactive control, by replacing manual segmentation required in the state of art methods. The most common primary brain tumors are gliomas, evolving from the cerebral supportive cells. For clinical follow-up, the evaluation of the pre- operative tumor volume is essential. Tumor portions were automatically segmented from 2D MR images using morphological filtering techniques. These seg- mented tumor slices were propagated and modeled with the software package. The 3D modeled tumor consists of gray level values of the original image with exact tumor boundary. Axial slices of FLAIR and T2 weighted images were used for extracting tumors. Volumetric assessment of tumor volume with manual segmentation of its outlines is a time-consuming proc- ess and is prone to error. These defects are overcome in this method. Authors verified the performance of our method on several sets of MRI scans. The 3D modeling was also done using segmented 2D slices with the help of a medical software package called 3D DOCTOR for verification purposes. The results were validated with the ground truth models by the Radi- ologist.
Description:
J. Biomedical Science and Engineering, 2012, 5, 378-383