NISCAIR Online Periodicals Repository Collection: IJRSP Vol.41(3) [June 2012]

Compact dual band slotted patch antenna for wireless systems

Tue, 29 May 2012 22:58:59 GMT

Title: Compact dual band slotted patch antenna for wireless systems

Authors: Ambresh, P A; Hadalgi, P M; Hunagund, P V

Abstract: This paper presents the study on a slot-etched rectangular patch antenna directly fed by the 50 Ω semi miniature A-type (SMA) co-axial connector for wireless systems. The dual frequency behaviour by etching the slots on plane patch surface is studied experimentally. The proposed patch antenna has also achieved 28% compactness with a gain of 9.74 dB. Other antenna parameters such as antenna input impedance, voltage standing wave ratio (VSWR), return loss, gain and bandwidth are presented. Details of antenna geometry, patch design and experimental results are also presented. This antenna finds applications in WiMax, radar communication, WLAN, and fixed satellite service applications covering 3 – 4 GHz frequency range.

Page(s): 372-376

Variability of estimated dielectric constant obtained using theoretical models over Pacific Ocean in open sea for sea surface salinity varying from lower to higher values

Tue, 29 May 2012 22:58:59 GMT

Title: Variability of estimated dielectric constant obtained using theoretical models over Pacific Ocean in open sea for sea surface salinity varying from lower to higher values

Authors: Calla, O P N; Purohit, Uttra; Asopa, Pooja; Kalla, Abhishek; Dadhich, Harendra

Abstract: In this paper, the values of dielectric constant (ε) obtained by Blanch & Aguaca (B&A) as well as Klein & Swift (K&S) models using variable salinity in open seas in Pacific Ocean have been studied. The values of dielectric constant derived by B&A and K&S are compared with different salinities ranging 20-50 psu. The analysis has been done on eight days: three days in February and five days in March 2011. Each of these three days of February pair with the other three days of March before Tsunami and remaining two days of March taken after Tsunami pair with each other, in such a way that each pair have nearly same pass over Pacific Ocean and thus, in this way each of these four sets form the four different passes over Pacific Ocean near Japan. This analysis was initially done with Tsunami point of view over Japan which is under process but during this analysis, variability of ε has been seen using two models (B&A and K&S) for variable salinity and the analysis has been presented. This analysis shows that within certain acceptable limits both the models of K&S and B&A are useful for estimating dielectric constant of sea water and understanding the variability of estimated ε with sea surface salinities. The analysis also shows that the dielectric constant goes lower to higher value for B&A and higher to lower values for K&S with increase in the values of salinity.

Page(s): 367-371

Artificial neural network (ANN) for modelling earth’s magnetic field belonging to solar minimum observed at a low latitude station Alibag

Tue, 29 May 2012 22:58:59 GMT

Title: Artificial neural network (ANN) for modelling earth’s magnetic field belonging to solar minimum observed at a low latitude station Alibag

Authors: Unnikrishnan, K

Abstract: Artificial neural networks (ANNs) are well suited to environmental modelling as they are nonlinear, relatively insensitive to data noise, and perform reasonably well when limited data are available. By using solar flux (F10.7), day of the year, local time, and Ap as input, an appropriate ANN has been developed to model north-south component (X component) of earth’s magnetic field belonging to solar minimum period for Alibag (18.6°N, 72.87°E, geomagnetic latitude 10.37°N), a low latitude station of Indian sub-continent. For training the network three months, namely February, June, and September, were selected which represent three seasons winter, summer, and equinox, respectively of 2007 and 2008. Based on this analysis, it is observed that ANN model with 10 hidden neurons has good performance for 500 iterations. For testing the efficiency of ANN, hourly values of input and north-south component (X component) of earth’s magnetic field observed during January, October 2007 and May 2008 were used. To confirm the functional aspects of this model, similar investigations were carried out for other periods, January, October 2008, and May 2007. In this study, for the first time, artificial neural networks (ANNs) are utilised to develop a geomagnetic daily variation model for an Indian sub-continent station, Alibag.

Page(s): 359-366

Estimation of pressure drop and storm surge height associated to tropical cyclone using Doppler velocity

Tue, 29 May 2012 22:58:59 GMT

Title: Estimation of pressure drop and storm surge height associated to tropical cyclone using Doppler velocity

Authors: Pradhan, Devendra; Mitra, Anasuya; De, U K

Abstract: A study of five tropical cyclones in the Bay of Bengal has been conducted to estimate the pressure drop in the eye of the cyclone and associated storm surge height using Doppler velocity data. A new value of constant K (13.637) has been found in the empirical relation V_max = K√(P-Pc) between maximum velocity (V_max) and central pressure drop (P-P_c) in terms of maximum radial velocity measured by the Doppler Weather Radar (DWR) for coastal region of India. The present study provides an alternate method for estimating central pressure drop and expected storm surge height associated to a tropical cyclone. The study also reveals that the storm surge height estimated from Doppler velocity measurements for these cyclones is very close to the actual occurrence. The results of pressure drop estimates from Doppler velocity are in close agreement with the satellite estimates. It is also observed that DWR estimates are sometimes better than those from satellite. However, the limitation of DWR is the limited range of observation (400 km) and shorter duration of cyclone tracking.

Page(s): 348-358