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
Sebastian, Mathew; Joe, Jacob; Joseph, V P; Bijukumar, S; Raveendranath, U; Mathew, K T(John Wiley & Sons, March 5, 1999)
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Abstract:
This paper presents the design of a new type of corner reflector (CR) antenna and the experimental investigation of its radiation characteristics. The design involves the addition of planar parallel periodic strips to the two sides of a CR antenna. The position, angular orientation, and number of strips have a notable effect on the H-plane radiation characteristics of the antenna. Certain configurations of the new antenna are capable of producing very sharp axial beams with gain on the order of 5 dB over the square corner reflector antenna. A configuration that can provide symmetric twin beams with enhanced gain and reduced half-power beam width (HPBW) is also presented.
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
Raveendranath, U; Biju Kumar, S; Mathew, K T(IETE Technical Review, September , 1999)
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Abstract:
The performance of circular, rectangular and cross irises for the coupling of microwave power
to rectangular waveguide cavity resonators is discussed. For the measurement of complex
permittivity of materials using cavity perturbation techniques, rectangular cavities with high
Q-factors are required. Compared to the conventional rectangular and circular irises, the cross Iris
coupling structure provides very high loaded quality factor for all the resonant frequencies. The
proposes cross iris coupling structure enhances the accuracy of complex permittivity measurements.
A novel antenna configuration comprised of two circular
microstrip antennas (CMAs) resonating in the TMtt and TM2, modes,
producing radiation characteristics suitable for a mobile telephone handset,
is presented. The antennas operating at the same frequency are
placed back to back with a separation comparable to the thickness of a
typical handset. The radiation pattern consists of a region of reduced
radiation intensity, which minimizes the radiation hazards to the user
Description:
Microwave and Optical Technology Letters,VOL 23,issue 6.pp 370-372
Jianlang,Li; Liren,Liu; Yingchun,Guo; Huaisheng,Wang; Changhe,Zhou(Microwave and Optical Technology Letters, December 20, 1999)
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Abstract:
The transient interaction between a refraction index grating
and light beams during simultaneous writing and thermal fixing of
a photorefractive hologram is investigated. With a diffusion- and
photovoltaic-dominated carrier transport mechanism and carrier thermal
activation (temperature dependent) considered in Fe:LiNbO3 crystal, from
the standpoint of field-material coupling, the theoretical thermal fixing
time and the space-charge field buildup, spatial distribution, and temperature
dependence are given numerically by combining the band transport
model with mobile ions with the coupled-wave equation
Mridula, S; Jacob,George; Mohanan, P(Microwave and Optical Technology Letters, December 20, 1999)
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Abstract:
A novel antenna configuration comprised of two circular
micro strip antennas (CMAs) resonating in the TMtt and TM2, modes,
producing radiation characteristics suitable for a mobile telephone handset,
is presented. The antennas operating at the same frequency are
placed back to back with a separation comparable to the thickness of a
typical handset. The radiation pattern consists of a region of reduced
radiation intensity, which minimizes the radiation hazards to the user
Ceramic dielectric resonators in the BaO-RE2O3-TiO2 (RE=rare earth) system have been
prepared by the conventional solid state ceramic route. The dielectric properties have been
tailored by substitution of different rare earth oxides and by bismuth oxide addition. The
dielectric constants increased with Bi addition whereas the Q decreased. The temperature
coeffecient of the resonant frequency improved with bismuth addition.
A microwave dielectric ceramic resonator based on BaCe2Ti5O15 and Ba5Nb4O15 have been prepared by conventional solid state ceramic route. The dielectric resonators (DRs) have high dielectric constant 32 and 40 for BaCe2Ti5O15 and Ba5Nb4O15, respectively. The whispering gallery mode (WGM) technique was employed for the accurate determination of the dielectric properties in the microwave frequency range. The BaCe2Ti5O15 and Ba5Nb4O15 have quality factors (Q X F) of 30,600 and 53,000 respectively. The quality factor is found to depend on the azimuthal mode numbers. The temperature coefficient of resonant frequency (Tr) of BaCe2Ti5O15 and Ba5Nb4O15 have been measured accurately using different
resonant modes and are + 41 and + 78 ppm/K, respectively
Ceramic dielectric resonators in the BaO-RE2O3-TiO2 (RE = rare earth) system have been
prepared by the conventional solid state ceramic route. The dielectric properties have been
tailored by substitution of different rare earth oxides and by bismuth oxide addition. The
dielectric constants increased with Bi addition whereas the 0 decreased. The temperature
coefficient of the resonant frequency improved with bismuth addition
Mohanan, P; Raj,R K; Joseph,M; Paul,B(Department of Electronics, March 17, 2000)
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Abstract:
A compact single - feed muttiband planar antenna configuration suitable
for GPS, DCS. 2.4/5.8 GHz WLAN applications is presented.
The antenna has dimensions 38 x 3 x 1.6 mm and offers good
radiation and reflection characteristics in the above frequency bands.
The antenna has a simple geometry and can be easily fed using a 50
coaxial probe.
Sona,Kundukulam O; Manju,Paulson; Aanandan,C K; Mohanan, P; Vasudevan, K(Microwave and Optical Technology Letters, June 5, 2000)
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Abstract:
Experimental studies on a compact dual frequency microstrip
antenna are presented. This antenna configuration provides an
area reduction of 40% compared to a standard rectangular antenna
operating at the same frequency without much degradation of the gain.
The antenna structure can be modified to achieve the desired ratio
between the two resonant frequencies
Binoy,G S; Aanandan,C K; Mohanan, P; Vasudevan, K(Microwave and Optical Technology Letters, June 20, 2000)
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Abstract:
A novel dual frequency dual-polarized square microstrip
patch antenna embedded with a slot is presented. The proposed
antenna offers tunability of the frequency ratio between the two
frequencies by adjusting the slot dimensions. This configuration
also provides a size reduction up to -51 and 35% for the two modes
as compared to a square micro strip patch antenna
Zheng,Qinhong; Xie,Fuyao; Liang,Li; Wang,Ruili; Ou,Jiaming(Microwave and Optical Technology Letters, June 20, 2000)
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Abstract:
A new approach, the multipole theory (MT) method, is
presented for the computation of cutoff wavenumbers of waveguides
partially filled with dielectric. The MT formulation of the eigenvalue
problem of an inhomogeneous waveguide is derived. Representative
computational examples, including dielectric-rod-loaded rectangular and
double-ridged waveguides, are given to validate the theory, and to
demonstrate the degree of its efficiency
Biju Kumar, S; Raveendranath, U; Mohanan, P; Mathew, K T; Hajian,M; Ligthart, L P(Microwave and Optical Technology Letters, July 20, 2000)
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Abstract:
A simple and efficient method for determining the complex
permittivity of dielectric materials from both reflected and transmitted signals is presented. It is also novel because the technique is implemented using two pyramidal horns without any focusing mechanisms. The dielectric constant of a noninteractive and distributive (NID) mixture of dielectrics is also determined
Manju,Paulson; Mohanan, P; Sona,Kundukulam O(Microwave and Optical Technology Letters, September 5, 2000)
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Abstract:
A compact microstrip antenna with circular polarization radiation is demonstrated.A reducation in the required parameters for achieving CP radiation makes the present antenna design simpler
Raveendranath, U; Bijukumar, S; Mathew, K T(IEEE, December , 2000)
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Abstract:
A novel cavity perturbation technique using coaxial cavity resonators for the measurement of complex permittivity of liquids is presented. The method employs two types of resonators (Resonator I and Resonator II). Resonator I operates in the frequency range 600 MHz-7 GHz and resonator II operates in the frequency range 4 GHz-14 GHz. The introduction of the capillary tube filled with the sample liquid into the coaxial resonator causes shifts in the resonance frequency and loaded Q-factor of the resonator. The shifts in the resonance frequency and loaded Q-factor are used to determine the real and imaginary parts of the complex permittivity of the sample liquid, respectively. Using this technique, the dielectric parameters of water and nitrobenzene are measured. The results are compared with those obtained using other standard methods. The sources of errors are analyzed.