The standard separable two dimensional wavelet transform has achieved a great success in image
denoising applications due to its sparse representation of images. However it fails to capture efficiently the
anisotropic geometric structures like edges and contours in images as they intersect too many wavelet basis
functions and lead to a non-sparse representation. In this paper a novel de-noising scheme based on multi
directional and anisotropic wavelet transform called directionlet is presented. The image denoising in
wavelet domain has been extended to the directionlet domain to make the image features to concentrate on
fewer coefficients so that more effective thresholding is possible. The image is first segmented and the
dominant direction of each segment is identified to make a directional map. Then according to the
directional map, the directionlet transform is taken along the dominant direction of the selected segment.
The decomposed images with directional energy are used for scale dependent subband adaptive optimal
threshold computation based on SURE risk. This threshold is then applied to the sub-bands except the LLL
subband. The threshold corrected sub-bands with the unprocessed first sub-band (LLL) are given as input
to the inverse directionlet algorithm for getting the de-noised image. Experimental results show that the
proposed method outperforms the standard wavelet-based denoising methods in terms of numeric and
visual quality
Description:
Signal & Image Processing : An International Journal (SIPIJ) Vol.3, No.6, December 2012
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.
Saou, Wen Su; Kin, Lu Wong(Microwave and Optical Technology Letters, September 20, 2005)
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Abstract:
novel design of at internal PIFA integrated with an
RF-shielding metal case for application in a clamshell or fielder-tvpe
mobile phone is presented. The integrated PIFA has a bent and tapered
radiating arm in order to easily fit in the casing of the clamshell mobile
phone as an internal antenna. The integrated PlEA can also provide a
wide operating bandwidth fir UM7S (1920-2170 MHz) operation. In
addition, for the clamshell mobile phone in either the talk or standby
condition, only a small effect on the operating bandwidth of the integrated
PIFA is obtained. The experimental results of the proposed design are presented
Haddud,T A; Al-Mansoori,M H; Zamzuri,A K; Shaharudin,S; Abdullah,M K; Mahdi,M A(Microwave and Optical Technology Letters, April 20, 2005)
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Abstract:
In this paper, the generation of a multiwavelength laser
source from a Brillouin -Erbium fiber laser in the long wavelength band
(L-band) region is experimentally demonstrated. The proposed laser
system utilizes a Fabrv-Perot cavity formed by fiber-loop mirrors.
Twenty-four lines of Brillouin-Stokes with line spacings of 10 GHz are
obtained in the L-band region
Anupam,Chandran R; Thomaskutty,Mathew; Aanandan,C K; Mohanan, P; Vasudevan, K(Microwave and Optical Technology Letters, February 5, 2004)
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Abstract:
A novel technique for backscattering reduction for both TE
and TM polarisation, employing a metallo-dielectric structure based on
Sierpinski carpet fractal geometry, is reported. A reduction in backscattered
power of --30 dB is obtained for normal incidence in the X-band for the
structure using the third iterated stage of the fractal geometry
Lethakumary,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
Sreedevi, Menon K; Lethakumary,B; Bijumon, P V; Sebastian,M T; Mohanan, P(Microwave and Optical Technology Letters, May 5, 2005)
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Abstract:
In this paper, the advantages of using L-shaped microviij)
feed to e.tcite a rectangular dielectric resonator cuuenna (DRA) by elemanagnetic
coupling are presented. This feeding technique enhances the
hardsvidth and gain of the antenna without affecting its size. The experimental
re srdts are validated using Fidelity software based on the finitedifference
tine-domain (FDTD) method
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
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
Jitha, B; Bybi, P C; Aanandan,C K; Mohanan, P(John Wiley & Sons, June , 2008)
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Abstract:
Design of a compact microstrip band reject filter is proposed. The device consists of an Open Loop Rectangular Resonator (OLRR) coupled to a microstrip line. The transmission line has a U-bend which enhances the coupling with the OLRR element and reduces the size of the filter. The filter can be made tunable by mounting variable capacitance to the system. Simulated and experimental results are presented.
Zhongyou,Yan(Microwave Engineering Group,Department of Electronics, January 5, 2002)
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Abstract:
patch resonator with a via connecting ground plane is
proposed and studied experimentally. The resonant frequency of this
patch resonator is tunable up to about 34 % by adjusting the via position
in the center line. The lowest resonant frequency of this patch resonator
has been reduced by more than 64% of the same size patch resonator
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
The microwave dielectric properties of (I -x)CaTiO3-xSm(Mg1/2Tit,2)O3(0.1 <-x< 1.0) have been investigated. The
system forms a solid solution throughout the entire compositional range. The dielectric constant decreases from 86 to 25 as x
varies from 0.1 to 1.0. The Qxf varies non-linearly and increases for composition with x> 0.6. The nonmonotonic variation
with composition x is more pronounced in Tt than in er. The microwave dielectric properties indicate the possibility of a phase
transformation for x between 0.4 and 0.5
microwave dielectric properties of ceramics based on Ba(Mgv3Ta(2-2x)t3W,t3Tixt3)O3 is investigated as a function of x. The
15 densification as well as dielectric properties deteriorate with increase in the substitution levels of (Ti 1,3W113)333 + at (Ta213)3.33+ site
16 in Ba(Mg113Ta213)03. The rt is approaching zero between x = 0.1 and 0.15 in Ba(Mg it3Ta(2-2,,.)t3W,it3Ti,Tt3)O3 where quality factor is
17 reasonably good (Qu x f = 80,000-90,000 GHz). The Ba(Mg1,3Ta(2_,013W,13Ti,,13)03 with x = 1.0 has e, = 15.4, rf= -25.1 ppm/
18 "C, Q„ x f = 35,400 GHz
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
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