NOPR Collection:

FTFN based dual inputs current-mode allpass inverse filters

2005-06-01T00:00:00Z

Title: FTFN based dual inputs current-mode allpass inverse filters Authors: Shah, N A; Malik, M A Abstract: In this study, four new configurations implementing first-order current-mode allpass inverse filter signals are presented. The proposed generic circuit with two inputs and a single output employs a single FTFN, three resistors and a capacitor with both the inputs supporting the first-order allpass inverse responses separately. The topologies offer high output impedance, which enable easy cascading in current-mode. The realizability condition is simple and temperature invariant, being in the ratio of two grounded resistors. The additional advantage of the circuit is that the phase can be controlled by adjusting the values of passive components without disturbing the realizability condition. The tracking error performance for the filters has also been studied. The simulation results are also included. Page(s): 206-209

Potential and field distribution in a cylindrical tube filled with a dielectric material with a centre hole

2005-06-01T00:00:00Z

Title: Potential and field distribution in a cylindrical tube filled with a dielectric material with a centre hole Authors: Das, B N; Gayen, Arun; Poddar, D R Abstract: The paper presents a method of analysis of potential and field distribution in a cylindrical tube (metallic), covered at both ends with metallic plates, and containing a dielectric cylindrical shell whose axis coincides with the axis of the cylinder. The cylindrical surface and lower end are maintained at ground potential and the top plate is insulated and maintained at high potential. The resulting Laplace's equation is solved using the method of separation of variables. The constants appear in the resulting equation are found from the boundary conditions followed by representation of the functions satisfying orthogonality condition in cylindrical co-ordinates. If the field intensity exceeds the breakdown limit, the resulting breakdown of the gas leads to plasma generation inside the structure, which can provide a convenient method of generation of laser beam. Page(s): 197-205

Theoretical Z-R relationship for precipitating systems using Mie scattering approach

2005-06-01T00:00:00Z

Title: Theoretical Z-R relationship for precipitating systems using Mie scattering approach Authors: Rao, Usha N; Sarkar, Abhijit; Mohan, M Abstract: Making use of Mie scattering formulation from the classical electromagnetic theory, backscattering efficiency and radar reflectivity have been derived for a wide range of rain rates. The coefficients of Z-R (Z = radar reflectivity factor, R = rain rate, mm/h) relationships have been theoretically computed for 2.84 GHz (used in coastal Doppler radars), 13.8 GHz (used in the space-borne precipitation radar on-board TRMM satellite) and also 35.5 GHz (to be used in the forthcoming Global Precipitation Mission Radar). The Mie scattering results were compared with those obtained in the Rayleigh approximation. In the present work, analyses have been carried out for the well known Marshall-Palmer and Log-normal dropsize distributions. The theoretical approach described here however allows for any other dropsize distribution of precipitating system and operating radar frequency. Page(s): 191-196

TEC derived from incoherent scatter measurements during solar maximum and their comparison with IRI-2001 model

2005-06-01T00:00:00Z

Title: TEC derived from incoherent scatter measurements during solar maximum and their comparison with IRI-2001 model Authors: Sethi, N K; Pandey, V K Abstract: The diurnal and seasonal variations of the total electron content (TEC), derived from high resolution electron density profiles measured with the Arecibo (18.4°N, 66.7°W, dip 50^oN) incoherent scatter radar, are examined during high sunspot activity period (1989-90). Median values of TEC are then obtained at each hour during different seasons and compared with those obtained from the latest available International Reference Ionosphere (IRI-2001) model. The diurnal variations of TEC show more or less similar trend during all the seasons (i.e. maximum around daytime and minimum around midnight) with the largest values of TEC during equinox. The variability of TEC is larger at night than by day during all the seasons. Comparison of the diurnal variation of the observed median values of TEC with those predicted by the IRI model reveals, in general, similar trend during all the seasons and at all local times except during winter, when the IRI exhibits diurnal peak of TEC at around 0900 hrs LT, and the observed median peak occurs at around 1400 hrs LT. Discrepancies between the IRI and the median values exceed 40% during nighttime for winter and equinox. However, during daytime, they are less than 20% for all the seasons, except w inter morning hours. The TEC peak content increases by a factor of around 4 from solar minimum (1975-1 976) to solar maximum (1989-1990). Page(s): 184-190