Mohanan, P; Girijavallabhan, C P; Aanandan,C K; K G Nair(Indian Journal of Radio & Space Physics, February , 1984)
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Abstract:
A forward - biased point contact germanium signal diode placed inside a waveguide section along the E -vector is found to
introduce significant phase shift of microwave signals . The usefulness of the arrangement as a phase modulator for microwave
carriers is demonstrated. While there is a less significant amplitude modulation accompanying phase modulation , the insertion
losses are found to be negligible. The observations can be explained on the basis of the capacitance variation of the barrier layer
with forward current in the diode
Mridula, S; Anila, P V; Indhu, K K; Nijas, C M; Sujith, R; Mohanan, P(Wiley Subscription Services, Inc., A Wiley Company, March 1, 2014)
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Abstract:
An electrically small, broadband-modified, truncated
ground metamaterial EZ antenna is presented. This, a modified EZ
antenna system, achieves a larger bandwidth of the order of 650 MHz
by adjusting the metamaterial-inspired meandered ground element fed
by a top loaded monopole. The design is devoid of the large ground
planes and the external parasitic elements used in conventional
designs for achieving proper impedance matching characteristics. The
antenna requires a small foot print of kg/5 3 kg/10, where kg is the
guided wavelength corresponding to the lowest frequency of operation,
when printed on a substrate of dielectric constant 4.4 and thickness
1.6 mm. The antenna offers a 2:1 VSWR bandwidth from 750
MHz to 1.4 GHz, which covers CDMA, GSM, and ISM bands
Description:
MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 56, No. 3, March 2014
Mridula, S; Sreedevi, Menon K; Lethakumary,B; Binu, Paul; Aanandan,C K; Mohanan, P(Microwave and Optical Technology Letters, July 20, 2002)
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Abstract:
A broadband rectangular tnicrostrip antenna utilizing
an electromagnetically coupled L-strip feed is presented. Experimental
study shows a 2:1 VSWR bandwidth of a 10% and excellent
cross-polarization performance with a radiation coverage almost as
same as that of the rectangular microstrip antenna fed by conventional
methods. The variation of bandwidth for different feed parameters is also studied. The proposed antenna is suitable for broadband
communications
Mridula, S; Sarah, Jacob; Aanandan,C K; Shameena, V A; Mohanan, P; Vasudevan, K(Wiley Periodicals, December 2, 2011)
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Abstract:
A compact coplanar waveguide-fed (CPW) monopole antenna for ultra-wideband
wireless communication is presented. The proposed antenna comprises of a CPW-fed
beveled rectangular patch with a modified slotted ground. The overall size of the antenna is
30 mm 27 mm 1.6 mm. The lower edge of the band is attained by properly decoupling
the resonant frequencies due to the extended ground plane and the beveled rectangular
patch of the antenna. The upper edge of the radiating band is enhanced by beveling the
ground plane corners near the feed point. Experimental results show that the designed
antenna operates in the 2.7–12 GHz band, for S11 10 dB with a gain of 2.7–5 dBi. Both
the frequency domain and time domain characteristics of the antenna are investigated using
antenna transfer function. It is observed that the antenna exhibits identical radiation patterns
and reasonable transient characteristics over the entire operating band
Description:
International Journal of RF and Microwave Computer‐Aided Engineering,VOL 22,issue 5,pp 594-602
Haskins, P M; Dahele, J S(Department of Electronics, March 14, 1996)
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Abstract:
Two three-clement polarisation-agile active microstrip patch
arrays have been developed . The radiating elements are square
patches each with two transistors mounted on adjacent edges. The
patches radiate orthogonal modes , the relative phase of which can
be varied. Radiation patterns show good agreement with
predictions from theory, in both linear and circular polarization,
and no grating lobes were observed
Sangster,A J(Microwave and Optical Technology Letters, September , 1991)
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Abstract:
A new microstrip antenna element is described which exhibits polarization
agility. This is achieved by employing a T-slot radiator
which is driven by the edge fields of a balanced microstrip line. The
balanced line can support two propagating modes. namely. an even
mode and an odd mode, and be switching between these modes. the
orthogonal arms of the T-slot radiator are separately excited thus
forming orthogonally polarized radiated fields. A nucrostrip patch
antenna, which displays polarization agility using the sane mechanism,
is also described
Choudhury, P K(Microwave and Optical Technology Letters, November 25, 2002)
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Abstract:
A fairly rigorous analytical treatment of the power characteristics
of dielectric optical waveguides with Piet Hein core-cross
sectional geometry is presented in this paper. This kind of wareguide
structure would be advantageous owing to the absence of corners,
which are found in rectangular guides, resulting in undesirable loss (hit
to the scattering of light. In order to simplify this theoretical approach.
em approximation of vanishing refractive index difference between the
guiding and the non-guiding sections is implemented. The variation eJ
logarithmic power is shown for different dimensions of the core, corresponding
to different azimuthal modal indices. It is found that the nutlet
with higher index values carry less logaritlunic power in the lower tail
of the propagation 's constant range, and this feature affects the higher
tail. A better kind of uniformity of the power distribution is observed
near the higher tail of the range of propagation Constants
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)
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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)
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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)
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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)
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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)
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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)
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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)
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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)
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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)
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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.