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
Mridula,S; Sreedevi,Menon K; Mohanan,K; Bijumon,P V(Microwave and Optical Technology Letters, February 20, 2004)
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Abstract:
The radiation characteristics of a microstrip-line-excited rectangular dielectric resonator antenna (DRA) are studied experimentally.The radiation charactristics and excitation of different modes are highly influenced by the orientation of the DR,feed line parameters ,and finite size of the ground plane
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
Paulson,M; Sona,Kundukulam O; Aanandan,C K; Mohanan,P(Department of Electronics, September , 2001)
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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.
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.
Sona,Kundukulam O; Manju,Paulson; Aanandan,C K; Mohanan,P(Microwave Engineering Group,Department of Electronics, April 20, 2002)
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Abstract:
Design equations are presented for calculating the resonance frequencies for a
compact dual frequency arrow-shaped microstrip antenna. This provides a fast and simple
way to predict the resonant frequencies of the antenna. The antenna is also analyzed using the
IE3D simulation package. The theoretical predictions are found to be very close to the
IE3D results and thus establish the validity of the design formulae
Lethakumari,B; Sreedevi,Menon K; Aanandan,C K; Vasudevan,K; Mohanan,P(Microwave and Optical Technology Letters, July 20, 2004)
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Abstract:
This paper presents the outcome of the experimental studies
performed on L-strip fed compact rectangular microstrip antenna.
The effect of the feed parameters upon the characteristics of the antenna
is studied in detail. The antenna offers an impedance bandwidth of
nearly 20% and is suitable for broadband applications
The design and implementation of a novel asymmetric coplanar
waveguide (ACPW ) band rejection filter using defected ground
structure ( DGS) is presented . The proposed ACPW DGS technology
provides band gap characteristics with only one cell in the lateral
ground plane . The equivalent circuit model of the proposed DGS
unit section is described . Measurements of ACPW DGS showed good
agreement with simulation and the proposed model
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
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