| Abstract: | Design, development and experimental observations of a L: band printed dipole antenna is presented.Bandwidth enhancement is achieved by end-loading or the dipole arms. Using the present technique Impedance bandwidth van be enhanced up to 50% without degrading the efficiency of the antenna. |
| URI: | http://dyuthi.cusat.ac.in/purl/1435 |
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| Novel wide band printed dipole antenna.PDF | (1.287Mb) |
| Abstract: | A forward - biased point contact germanium signal diode placed inside a waveguide section along the E -vector is found to introduce significant phase shift of microwave signals . The usefulness of the arrangement as a phase modulator for microwave carriers is demonstrated. While there is a less significant amplitude modulation accompanying phase modulation , the insertion losses are found to be negligible. The observations can be explained on the basis of the capacitance variation of the barrier layer with forward current in the diode |
| URI: | http://dyuthi.cusat.ac.in/purl/1432 |
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| Phase modulatio ... ermanium signal diodes.PDF | (882.1Kb) |
| Abstract: | A broadband rectangular tnicrostrip antenna utilizing an electromagnetically coupled L-strip feed is presented. Experimental study shows a 2:1 VSWR bandwidth of a 10% and excellent cross-polarization performance with a radiation coverage almost as same as that of the rectangular microstrip antenna fed by conventional methods. The variation of bandwidth for different feed parameters is also studied. The proposed antenna is suitable for broadband communications |
| URI: | http://dyuthi.cusat.ac.in/purl/1385 |
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| PLANAR L-STRIP ... AND MICROSTRIP ANTENNA.PDF | (716.7Kb) |
| Abstract: | Ceramics of composition BaO-Ln2O3-STiO2 have been prepared with four elements (Ln=La,Pr,Nd.Sm) by a conventional solid state ceramic preparation route and the dielectric properties measured in the microwave frequency range |
| URI: | http://dyuthi.cusat.ac.in/purl/1439 |
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| Dielectric reso ... (Ln = La, Pr, Nd, Sm).PDF | (3.733Mb) |
| Abstract: | The dielectric ceramics BaNd2Ti3Oto, BaNd2Ti4O12 and BaNd2Ti5O14 have been prepared by Conventional solid state ceramic route. The sintered ceramic samples have been characterized by X-ray diffraction and Scanning Electron Microscopy (SEM). The dielectric properties in the microwave frequency range have been measured using conventional microwave dielectric resonator methods. The BaNd2Ti1O10, BaN2Ti4O12 and BaNd2Ti5O14 have dielectric constants (Er) ~ 60, 84 and 77 respectively. They have relatively high quality factors |
| URI: | http://dyuthi.cusat.ac.in/purl/1444 |
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| Preparation,cha ... BaO-Nd2O3-TiO2 system.PDF | (2.220Mb) |
| 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) |
| URI: | http://dyuthi.cusat.ac.in/purl/1494 |
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| Preparation, ch ... Y, Yb and In] ceramics.PDF | (4.468Mb) |
| Abstract: | In this paper, we present an effective excitation of a reelangular dielectric resonator antennas (DRA) with a conductor-hacked coplanar waveguide (CB-CPW). The radiation and resonance characteristics are found to van,, depending on the orientation of the DR on doe coplanar feed line. The effect of finite and infinite ground planes of CB-CPIV on the radiation characteristics of the rectangular DRA is studied. The orientation and position of the DR are optimized for maximum gain and bandwidth. The optimized antenna ,geometry offers --10.46 dBi gain and 7.5% bandwidth with low cross-polar radiation characteristics |
| URI: | http://dyuthi.cusat.ac.in/purl/1426 |
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| Rectangular die ... uctor-backed co-planar.PDF | (1.069Mb) |
| Abstract: | 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 |
| URI: | http://dyuthi.cusat.ac.in/purl/1353 |
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| Resonance frequ ... act microstrip antenna.PDF | (701.4Kb) |
| 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. |
| URI: | http://dyuthi.cusat.ac.in/purl/671 |
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| Resonance frequ ... crostrip antenna Manju.pdf | (357.4Kb) |
| 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. |
| URI: | http://dyuthi.cusat.ac.in/purl/670 |
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| Resonant freque ... icrostrip antenna Sona.pdf | (217.3Kb) |
| Abstract: | A simple and efficient method for determining the complex permittivity of dielectric materials from both reflected and transmitted signals is presented. It is also novel because the technique is implemented using two pyramidal horns without any focusing mechanisms. The dielectric constant of a noninteractive and distributive (NID) mixture of dielectrics is also determined |
| URI: | http://dyuthi.cusat.ac.in/purl/1374 |
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| Dyuthi-P00418.pdf | (452.6Kb) |
| 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 |
| URI: | http://dyuthi.cusat.ac.in/purl/1382 |
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| Slot coupled sq ... al-frequency operation.PDF | (1.351Mb) |
| 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 |
| URI: | http://dyuthi.cusat.ac.in/purl/1378 |
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| Slot-loaded com ... al-frequency operation.PDF | (1.081Mb) |
| Abstract: | 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 |
| URI: | http://dyuthi.cusat.ac.in/purl/1361 |
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| A Strip-Loaded Feed-Horn Antenna.PDF | (988.8Kb) |
| Abstract: | 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 |
| URI: | http://dyuthi.cusat.ac.in/purl/1438 |
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| Sreemoolanadhan H and others.PDF | (2.413Mb) |
| 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] |
| URI: | http://dyuthi.cusat.ac.in/purl/1452 |
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| Synthesis chara ... ecommunication systems.PDF | (1.309Mb) |
| Abstract: | 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 |
| URI: | http://dyuthi.cusat.ac.in/purl/1449 |
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| Synthesis , cha ... 06 dielectric ceramics.PDF | (1.260Mb) |
| Abstract: | 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 |
| URI: | http://dyuthi.cusat.ac.in/purl/1445 |
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| Tailoring the m ... mpositional variations.PDF | (4.793Mb) |
| Abstract: | 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 |
| URI: | http://dyuthi.cusat.ac.in/purl/1455 |
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| Tailoring the m ... 1 _X Y,TiTa06 ceramics.PDF | (3.705Mb) |
| Abstract: | 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 |
| URI: | http://dyuthi.cusat.ac.in/purl/1492 |
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| Temperature sta ... substrate applications.PDF | (3.226Mb) |
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