| Abstract: | The effect of dopants with different valencies and ionic radii on the densification, structural ordering, and microwave dielectric properties of Ba(Mg1t3Tazt3)O3 (BMT) is investigated. It is found that dopants such as Sb,05, MnO, ZrO,, WO1, and ZnO improve the microwave dielectric properties of BMT. Addition of trivalent dopants is detrimental to the cation ordering and dielectric properties of BMT. A correlation between the microwave dielectric properties of BMT and ionic radii of the dopant has been established. The variation of the dielectric properties of pure and doped BMT at cryogenic temperatures is also discussed |
| URI: | http://dyuthi.cusat.ac.in/purl/1489 |
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| The effect of d ... o.33Ta0.67)03 ceramics.PDF | (5.114Mb) |
| URI: | http://dyuthi.cusat.ac.in/purl/1491 |
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| Effect of Nonst ... of Ba(Mgo.33Tao.67)03.PDF | (6.590Mb) |
| Abstract: | 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 |
| URI: | http://dyuthi.cusat.ac.in/purl/1495 |
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| Effect of Nonst ... of Ba(Mgo.33Tao.67)03.PDF | (6.590Mb) |
| 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 |
| URI: | http://dyuthi.cusat.ac.in/purl/1389 |
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| Enhanced bandwi ... dielectric resonators.PDF | (1.874Mb) |
| Abstract: | Results of exhaustive study of the effect of metallic flanges on H-plane radiation characteristics of V-slot waveguide antenna are presented . It has been established that the beam can be sharpened or broadened by varying the flange angle . The adjustment of the flange angle and flange width would further improve the radiation pattern , yielding optimum efficiency from the flanged system |
| URI: | http://dyuthi.cusat.ac.in/purl/1436 |
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| An experimental ... slot waveguide antenna.PDF | (1.063Mb) |
| Abstract: | A new group of compounds with composition (Ba5-xSrx) Nb4015, having high permittivity and low loss have been prepared and characterized in the microwave frequency region . X-ray diffraction studies showed that monophase compound existed for all values of x from 0 to 5. Microwave dielectric properties such as and c f showed smooth variation with x , while the unloaded quality factor (Qu) showed remarkable improvement with x |
| URI: | http://dyuthi.cusat.ac.in/purl/1440 |
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| Sreemoolanadhan,H & Sebastian,M.T.PDF | (1.655Mb) |
| 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 |
| URI: | http://dyuthi.cusat.ac.in/purl/1425 |
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| L-strip-fed wid ... tric resonator antenna.PDF | (932.7Kb) |
| 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 |
| URI: | http://dyuthi.cusat.ac.in/purl/1369 |
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| Microstrip ante ... uced radiation hazards.PDF | (1.152Mb) |
| Abstract: | 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 |
| URI: | http://dyuthi.cusat.ac.in/purl/1446 |
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| Microwave chara ... ng gallery mode method.PDF | (2.989Mb) |
| Abstract: | 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 |
| URI: | http://dyuthi.cusat.ac.in/purl/1453 |
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| Microwave diele ... 3 [0. 1 _x 1] ceramics.PDF | (2.946Mb) |
| Abstract: | 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 |
| URI: | http://dyuthi.cusat.ac.in/purl/1488 |
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| Microwave diele ... 3Wx3Tixf3) 03 ceramics.PDF | (3.228Mb) |
| Abstract: | 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 |
| URI: | http://dyuthi.cusat.ac.in/purl/1493 |
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| Microwave diele ... -2CeO2-nTiO2 ceramics.PDF | (3.306Mb) |
| Abstract: | Dielectric resonator ceramics with composition formula Ba[(D3+0.3 Bi0.2)Nb0.5]O3,where D3+=Y,Pr,Sm,Gd,Dy and Er,were prepared by the conventional ceramic preparation route |
| URI: | http://dyuthi.cusat.ac.in/purl/1441 |
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| Microwave diele ... Y, Pr, Sm, Gd, Dy, Er).PDF | (2.529Mb) |
| Abstract: | A circular miqrostrip antenna with a modified structure is presented. By adjusting the feed location along the circumference of the patch it is possible to match the antenna with a C microstrip line of any impedance. The impedance bandwidth and radiation characteristics are unaffected by this structural V modification. |
| URI: | http://dyuthi.cusat.ac.in/purl/674 |
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| Modified circular patch antenna Dey.pdf | (199.5Kb) |
| Abstract: | A simple technique to improve the impedance bandwidth of a circular microstrip patch antenna using two sectorial slots is proposed. Using this design more than 5% impedance bandwidth is obtained. The added advantage of this new antenna is that it can be fed by a 50- microstrip line |
| URI: | http://dyuthi.cusat.ac.in/purl/1366 |
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| A new broadband circular patch antenna.PDF | (1.429Mb) |
| Abstract: | A new compact dual-band, dual-polarized microstrip antenna is presented. 7'iris antenna resonates at two frequencies with different polarizations: a linearly polarized one for terrestrial communication, and a circularly polarized one for satellite mobile communication. This antenna also provides an area reduction of 70% compared to a standard rectangular patch antenna |
| URI: | http://dyuthi.cusat.ac.in/purl/1376 |
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| A new compact d ... zed microstrip antenna.PDF | (1.044Mb) |
| Abstract: | A new microstrip antenna geometry with considerable reduction in size, with similar radiation characteristics to those of an equivalent rectangular patch antenna is proposed. A relationship has been suggested for fmding out the resonant frequency of the new geometry, and its validity has been established by the experimental results. Without increasing the aperture area, this geometry also offers a facility for considerably reducing the resonant frequency compared to conventional patches. |
| URI: | http://dyuthi.cusat.ac.in/purl/673 |
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| New compact microstrip antenna Jacob.pdf | (248.7Kb) |
| Abstract: | New dielectric ceramics with formula BaTi3Nb4, O„ and Ba6Til4Nbz039 have been prepared and characterized. BaTi3Nba017 was densified to 92% of TD after firing at 1310 oC for 4 h. However, Ba6Ti 1 4Nb2O39 fired under optimized conditions (1260 ` C for 4 h) showed only 85% TD together with secondary phase. The crystal system of both of the compositions is orthorhombic |
| URI: | http://dyuthi.cusat.ac.in/purl/1443 |
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| New high permit ... TiO2-Nb2O5 composition.PDF | (2.094Mb) |
| Abstract: | compact multihand planar octagonal-shaped microstrip antenna simultaneously suitable for mobile communication and blue tooth application is presented. The antenna provides sufficient isolation benveen the two operating bands and an area reduction of -29 % with respect to a circular patch operating in the same band |
| URI: | http://dyuthi.cusat.ac.in/purl/1384 |
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| A NEW MICROSTRI ... BLUETOOTH APPLICATIONS.PDF | (1.532Mb) |
| Abstract: | Simultaneous elimination of specular reflection and backscattered power from a plane metallic surface by simulated corrugated surfaces of constant period and variable strip width for TM polarisation is reported. This new configuration offers almost a ten-fold frequency bandwidth compared with a regularly spaced strip grating of the same size. |
| URI: | http://dyuthi.cusat.ac.in/purl/672 |
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| New simulated c ... characteristics Saji@.pdf | (262.5Kb) |
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