Hsieh,Gui-Bin; Chen,Ming-Huang; Wong,Kin-Lu Wong(IEE Electronics letters,UK, June 21, 2001)
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Abstract:
A novel technique for obtaining dual-hand circular polarization
(CP) radiation of a single-feed circular microstrip antenna in
proposed and demonstrated. By embedding two pain of arc shaped
slots of proper lengths close to the boundary of a circular
patch, and protruding one of the arc-shaped slots with a narrow
slit, the circular microstrip antenna can perform dual-hand CP
radiation using a single probe feed. Details of the antenna design
Binoy,G S; Aanandan,C K; Mohanan, P; Vasudevan, K(Microwave Engineering Group,Department of Electronics, January 5, 2002)
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Abstract:
A novel dual frequency design of a square microstrip antenna coaxially
fed along the diagonal with a chip capacitor mounted at the bottom of
the stub is introduced. This design provides enhanced area reduction and
good cross-polarization levels. The antenna design can be used as a compact
antenna system where limited size is a major requirement. The details of the
antenna design and experimental results are presented
Sona,Kundukulam O; Manju,Paulson; Aanandan,C K; Mohanan, P(Microwave and Optical Technology Letters, December 5, 2001)
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Abstract:
Dual frequency operation is achieved from a compact
microstrip antenna by loading a pair of narrow slots close to its radiating
edges. The two frequencies have parallel polarization planes and similar
radiation characteristics. The ratio between the two operating frequencies
can be tuned in the range (1.14-1. 24), which is much smaller than that
of similar designs. The above excellent radiation characteristics are
achieved along with an area reduction of - 75% compared to the
standard rectangular patch
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
Design and development of a new feed -horn antenna
with low sidelobe levels is reported . The E-walls of this
antenna are fabricated with low -loss dielectric substrate ,
periodicallyloaded with thin conducting strips . The antenna
is found to be simulating the radiation characteristics of metallic
Corrugated horns . This can be an ideal substitute for metallic
Corrugated horns with added advantages like light -weight and low
production cost
The (Ba1-x Srx) (Nd1/2, Nb1/2) O3 ceramics have been prepared by the conventional
ceramic route for different values of x. Addition of a small amount of
CeO2(1 wt%) as a sintering aid increased the density of the samples. The structure
and microstructure of the sintered samples are studied by X-ray diffraction
and SEM methods. The dielectric properties of the samples are measured in the
microwave frequency region as a function of composition. The dielectric constant
decreases as x increases. The coefficient of thermal variation of resonant
frequency decreases as the Sr content increases and goes to the negative side.
The dielectric properties of (Ba1-x Srx) (Nd1/2, Nb1/2) O3 are in the range suitable
for application as dielectric resonators in microwave circuits
Pazhoor Bijumon, Varghese; Mohanan, P; Mailadil, Thomas Sebastian(The Japan Society of Applied Physics, 2002)
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Abstract:
Microwave ceramic dielectric materials Ca5Nb2TiO12 and Ca5Ta2TiO12 have been prepared by a conventional solid-state
ceramic process. The structure was studied by X-ray diffraction and the dielectric properties were characterized at microwave
frequencies. The ceramics posses a relatively high dielectric constant, very low dielectric loss (Q5 x f > 30000GHz) and
small temperature variation of resonant frequency. These materials are potential candidates for dielectric resonator
applications in microwave integrated circuits. [DOI: 10. 1 143/JJAP.41.3834]
Dielectric ceramics based on solid solution phases of [RE1_x= REr]TiNb06, where REI_s = Nd, Pr, Sm and RE' = Dy, Gd and Y, were prepared by the conventional solid-state ceramic route for values of x. The ceramic samples are characterized by X-ray diffraction and microwave methods. Ceramics based on RE (Pr, Nd and Sm) belonging to aeschynite group shows positive value of Tf and those based on RE (Gd, Dy and Y) belonging to euxenite group show negative value of r f. The solid solution phases between the aeschynite and the euxenite group shows intermediate dielectric constant and r f values. The results indicate the possibility of tailoring the dielectric properties by varying the composition of the solid solution phases. The range of solid solubility of euxenite in aeschenite and aeschenite
in euxenite are different for different rare earth ions
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
Microwave dielectric ceramics based on GdTiNb,-,.Ta,O6 and Sml _.,Y,TiTa06 have been prepared by conventional solid state
method . The GdTiTaO6 and SmTiTaO6 have aeschenite structure with positive rr and GdTiNbO6 and YTiTaO6 have euxenite
structure with negative rr. The rr of the ceramics has been tuned by preparing solid solution phases between the aeschynites and
euxenites for a possible zero rr material . It is observed that GdTiNbt_YTa.,O6 undergoes a phase transition from aeschynite to
euxenite when x=0.75 and in Sml-,YxTiTa06 for x= 0.73. The microwave dielectric properties change abruptly near the transition
region . The rr value approaches zero near the phase transition region while the samples have poor sinterability and poor quality
factor . The unloaded quality factor, dielectric constant and the sign of rr of the solid solution phases are found to depend on the
average ionic radius of the rare earth ion in RE ,-5RE',TiTaO6. The boundary of the euxenite-aeschynite phase transition occurs at
an average ( RE) ionic radius of 0.915 A in Sm,_, Y,.TiTaO6 solid solution phases
The microwave dielectric properties of ZnAl2O4 spinels were investigated and their properties
were tailored by adding different mole fractions of Ti02. The samples were synthesized using the mixed
oxide rout.e. The phase purity and crystal structure were identified using X-ray diffraction technique.
The sintered specimens were characterized in the microwave frequency range (3-13 GHz). The ZnA12O4
ceramics exhibited interesting dielectric properties (dielectric constant (e,.) = 8.5, unloaded quality factor
(Q.) = 4590 at 12.27 GHz and temperature coefficient of resonant frequency (Tf) = -79 ppm/°C).
Addition of Ti02 into the spinel improved its properties and the Tf approached zero for 0.83ZnAl2O4-
0.17TiO2• This temperature compensated composition has excellent microwave dielectric properties (Cr _
12.67, Q, = 9950 at 10.075 GHz) which can be exploited for microwave substrate applications
Qinghe, Mao; John, Lit W Y(Microwave and Optical Technology Letters, November 20, 2002)
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Abstract:
The transient characteristics of an erbium-doped fiber
(F.DF) laser, which can switch between wavelengths. are investigated.
77te laser has a set of coupled linear cavities. The slow gain dynamics
of EDFs and the cross-gain saturation in the coupled cavities give rise
to delayed switching responses and relocation oscillations, which are
respertively measured to be l ins and 3.5 ms for the worst rase, and
which mar be decreased by increasing the pump power. Thus, the
switching speed of the laser may be higher than 100 Hz
Bijumon, P V; Sreedevi, Menon K; Suma,M N(Microwave and Optical Technology Letters, November 5, 2005)
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Abstract:
rectangular low-density, high-permittivity dielectric
resona or antenna (DRA) excited by T-shaped microstrip feed offering a
2:1 VSWR bandwidth of -22% at 2.975 GHz is reported. The design
methoaology and experimental results of the antenna are discussed. The
excellent gain and radiation performance of the proposed antenna
project: it as a potential candidate for telecommunication applications
Shyam S,Pattnaik; Dhruba C,Panda; Devi,S(Microwave and Optical Technology Letters, September 20, 2002)
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Abstract:
The mathematical formulation of empirically developed formulas Jirr the calculation of the resonant frequency of a thick-substrate
(h s 0.08151 A,,) microstrip antenna has been analyzed. With the
use qt' tunnel-based artificial neural networks (ANNs), the resonant frequency
of antennas with h satisfying the thick-substrate condition are
calculated and compared with the existing experimental results and also
with the simulation results obtained with the use of an IE3D software
package. The artificial neural network results are in very good agreement
with the experimental results
Hyunkieu,Yang; Sangseol,Lee(Microwave and Optical Technology Letters, December 5, 2001)
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Abstract:
The cutoff wavenumbers of higher order modes in circular
eccentric guides are computed with the variational analysis combined
with a conformal mapping. A conformal mapping is applied to the
variational formulation, and the variational equation is solved by the
finite-element method. Numerical results for TE and TM cutoff
wavenumbers are presented for different distances between the centers
and ratio of the radii. Comparisons with numerical results found in the
literature validate the presented method
Lethakumary,B; Sreedevi, Menon K; Priya,Francis; Aanandan,C K; Mohanan, P(Microwave and Optical Technology Letters, January 20, 2005)
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Abstract:
In this paper, we introduce a novel feeding technique for
bandwidth enhancement of a rectangular microstrip antenna This antenna
offers an impedance bandwidth of 22% without degrading the effciencv.
The effect of the feed parameters upon patch characteristics
such as resonant frequency, impedance bandwidth, and radiation pattern are studied in detail. The experimental results are verified using the
FDTD results
Sreedevi, Menon K; Lethakumary,B; Mohanan, P; Bijumon, P V; Sebastian,M T(Microwave and Optical Technology Letters, August 20, 2004)
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Abstract:
A broadband cylindrical dielectric resonator antenna
(DRA) energized with an L-strip feed is presented The novel exciting
technique achieves a 2:1 VSWR bandwidth of 18%. The variation of
bandwidth for different feed parameters is also studied
The design and development of an L-band printed dipole antenna.
optimized for wide-band applications near first resonance, is reported.
This design has achieved more than 48% impedance bandwidth
(VSWR 2:1), without degrading its overall radiation efficiency
Lethakumary,B; Sreedevi, Menon K; Aanandan,C K; Mohanan, P(Microwave and Optical Technology Letters, April 5, 2003)
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Abstract:
An electromagnetically coupled T-shaped microstrip feed
used to enhance the impedance bandwidth of a rectangular microstrip
antenna is reported. The proposed antenna offers a 2:1 VSWR bandwidth
of -36% with an increase in gain of 0.8 dB
Mathew, K T; Stephen,D S; Aanandan,C K; Mohanan, P; K G Nair(Department of Electronics, May 12, 1994)
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Abstract:
A trapezoidal strip grating surface that eliminates specular
reflections almost over the entire X -band frequency range for TM
polarization is reported This new grating structure overcomes the
bandwidth limitation of conventional rectangular strip grating surfaces