Xiong,X Z; Fusco,V F(Microwave and Optical Technology Letters, August 5, 2002)
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Abstract:
In this Letter a new physical model for metal-insulatormetal
CMOS capacitors is presented. In the model the parameters of the
circuit are derived from the physical structural details. Physical behaviors
due to metal skin effect and inductance have been considered. The
model has been confirmed by 3D EM simulator and design rules proposed.
The model presented is scalable with capacitor geometry, allowing
designers to predict and optimize quality factor. The approach has
been verified for MIM CMOS capacitors
Sona,Kundukulam O; Manju,Paulson; Aanandan,C K; Mohanan, P(Microwave and Optical Technology Letters, August 5, 2002)
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Abstract:
Development of a new compact circular-sided microstrip
antenna is presented. This antenna offers considerable area re- TABLE 2. Variation of Resonant Frequencies
duction compared to standard rectangular microstrip antenna designed
for the same frequency. Typical antenna design and
experimental results for circular polarization are also demonstrated.
77je antenna has a 3-dB axial ratio bandwidth of 1.5%
Sona,Kundukulam O; Manju,Paulson; Aanandan,C K; Mohanan, P(Microwave and Optical Technology Letters, September 20, 2002)
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Abstract:
Experimental and simulated results for a dual-port
dual-polarized microstrip antenna are presented. The antenna excites
two orthogonally polarized resonant frequencies providing an isolation
of -30 dB between the ports. The patch geometry consists of
two circular arcs of different radii with their centers displaced by a
distance. This new design offers an area reduction of -70% coinpared
to it standard rectangular microstrip antenna with a reduction
in gain of 1.7 dB
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
Sona,Kundukulam O; Paulson,M; Aanandan,C K; Mohanan, P; K G Nair(Department of Electronics, October , 2002)
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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.
Bagei, A M; Cetin, A E(IEE Electronics letters,UK, October 24, 2002)
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Abstract:
A method for computer- aided diagnosis of micro calcification clusters
in mammograms images presented . Micro calcification clus.eni which
are an early sign of bread cancer appear as isolated bright spots in
mammograms. Therefore they correspond to local maxima of
the image. The local maxima of the image is lint detected and they
are ranked according to it higher-order statistical test performed over
the sub band domain data
Bijumon, P V; Sreedevi, Menon K; Sebastian,M T; Mohanan, P(Microwave and Optical Technology Letters, November 20, 2002)
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Abstract:
A novel technique fitr the bat dividth enhancement of conventional
rectangular microstrip antenna is proposed in this paper. When a
high permittivity dielectric resonator of suitable resonant frequency was
loaded over the patch. the % bandwidth of the antenna was increased by
more than five tunes without much affecting its gain and radiation performance.
A much more improved bandwidth was obtained when the dielectric
resonator was placed on the feedline. Experimental study shows a 2:1
VSWR bandwidth of more than 10% and excellent cross polarization performance
with increased pass band and radiation coverage abnost the same
as that of rectangular microstrip antenna
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
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
Isuhak, Naseembeevi Jawahar; Narayana Iyer, Santha; Mailadil, Thomas Sebastian(Materials Reserach Society, December , 2002)
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Abstract:
Single-phase polycrystalline ceramics in the MO-La2O3-Ti02 (M = Ca, Sr, Ba)
system, such as cation-deficient hexagonal perovskites CaLa4Ti4O15, SrLa4Ti4O15,
BaLa4Ti4O15, and Ca2La4Ti5O18 and the orthorhombic phases CaLa4Ti5O17 and
CaLa8Ti9O31, were prepared through the solid-state ceramic route. The phases
and structure of the ceramics were analyzed through x-ray diffraction and scanning
electron microscopy. The microwave dielectric properties of the ceramics were studied
using a network analyzer. The investigated ceramics show high Er in the range 42 to
54, high quality factors with Q x f in the range 16,222 to 50,215 GHz, and low Tf in
the range -25 to +6 ppm3/°C. These high dielectric constant materials with high Q x f
up to 50,215 GHz are suitable for applications where narrow bandwidth and extremely
low insertion loss is necessary, especially at frequencies around 1.9 GHz
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)
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
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
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
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
The effect of glass additives on the densification , phase evolution, microstructure and microwave dielectric properties of Ba(Mg1;3
Ta2i3)03 (BMT) was investigated . Different weight percentages of quenched glass such as B203 , Si02, B203-SiO2, ZnO-B203,
5ZnO-2B2O3, Al203-SiO2, Na20-2B203.10H20, BaO-B203-SiO2, MgO-B203-SiO2, PbO-B203-SiO2 , ZnO-B203-SiO2 and
2MgO-Al203-5SiO2 were added to calcined BMT precursor . The sintering temperature of the glass -added BMT samples were
lowered down to 1300 °C compared to solid-state sintering where the temperature was 1650 °C. The formation of high temperature
satellite phases such as Ba5Ta4O15 and Ba7Ta6O22 were found to be suppressed by the glass addition . Addition of glass systems such
as B203, ZnO-B203, 5ZnO-2B203 and ZnO-B203-SiO2 improved the densification and microwave dielectric properties. Other
glasses were found to react with BMT to form low-Q phases which prevented densification . The microwave dielectric properties of
undoped BMT with a densification of 93 . 1 % of the theoretical density were Cr = 24 . 8, Tr = 8 ppm/°C and Q„ x f= 80,000 GHz. The
BMT doped with 1.0 wt% of B203 has Q„ x f = 124,700GHz, Cr = 24.2, and T f = -1.3 ppm /°C. The unloaded Q factor of 0.2 wt%
ZnO-B203-doped BMT was 136,500 GHz while that of 1.0 wt% of 5ZnO-2B203 added ceramic was Q„ x f= 141,800 GHz . The best
microwave quality factor was observed for ZnO -B203-SiO2 (ZBS) glass-added ceramics which can act as a perfect liquid-phase
medium for the sintering of BMT. The microwave dielectric properties of 0.2wt% ZBS-added BMT dielectric was
Q„ x f= 152,800 GHz, F,= 25.5, and Tr = - 1.5 ppm/°C
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
The BaO-2CeO2-nTiO2 ceramics with n = 3, 4 and 5 have been prepared with CeO2 as starting material . The ceramics have been
characterized using scanning electron microscopy , X-ray diffraction , Raman and X-ray photoelectron spectroscopy techniques. The
microwave dielectric properties have been measured using standard dielectric resonator techniques . BaO-2CeO2-3TiO2 (123),
BaO-2CeO2-4TiO2 ( 124) and BaO-2CeO2-5TiO2 ( 125) ceramics showed dielectric constants of 38, 27 and 32, respectively . All the
ceramics showed fairly good unloaded Q - factors . 124 and 125 compounds exhibited low tf values, while 123 showed a high rf value
Dongsheng,Qi; Binhong,Li; Yabin,Zhang; Haitao,Liu(Microwave and Optical Technology Letters, February 3, 2004)
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Abstract:
A novel compact single-layer dual frequency microstrip
antenna which uses an H-shaped geometry with two U-shaped slots embedded
near the radiation edges, is presented. By changing the design parameters, the lower and higher resonant frequencies can be controlled
easily, and a range of frequency ratios (1.716-2.363) can be
obtained in this design. For the two operating frequencies of the proposed
antenna, the same polarization planes and broadside radiation
patterns are achieved. Compared to the regular dualfrequency patch
antenna, this antenna can realize a significant size reduction
Monz, Cabrera J; Diaz, Morcillo A; Pedreno, Molina L; Sanchez, Hermandez D(Microwave and Optical Technology Letters, February 4, 2004)
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Abstract:
Usage of a dielectric multilayer around a dielectric Sample
is studied as a means for improving the efficiency in multimode microwave-
heating cavities. The results show that by using additional dielectric
constant layers the appearance of undesired reflections at the
sample-air interface is avoided and higher power -absorption rates
within the sample and high -efficiency designs are obtained