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Slot-fed wideband dielectric resonator antenna for wireless applications

2011-01-15T16:30:24Z

Title: Slot-fed wideband dielectric resonator antenna for wireless applications Authors: Hadalgi, P M; Madhuri, R G; Mallikarjun, S L Abstract: In this paper, a slot-fed dielectric resonator antenna (DRA) with wideband operations in 4-6 GHz frequency band is presented. Slot represents coupling mechanism between resonators and the microstrip line. The DRA and slot are both resonant structures. The microstrip feed line is positioned at right angle to the center of the slot for efficient coupling. Together they yield a double resonant structure with low cross-polarization levels and identical radiation patterns. With proper design, the two resonances can be merged to achieve wide bandwidth. The rectangular dielectric resonator placed at the center of the rectangular ring slot provides an impedance bandwidth of 42.1%. The return loss and radiation patterns of these are presented. Page(s): 372-375

Inter-comparison of aerosol optical depth from the Multi-Wavelength Solar Radiometer with other radiometric measurements

2011-01-21T16:30:25Z

Title: Inter-comparison of aerosol optical depth from the Multi-Wavelength Solar Radiometer with other radiometric measurements Authors: Kompalli, Sobhan Kumar Abstract: The Multi-Wavelength Solar Radiometer (MWR), designed and developed in the Space Physics Laboratory, has been extensively used by several research institutions across the country for estimating columnar spectral aerosol optical depth (AOD), the most important parameter needed for assessing the impact of aerosols on regional aerosol forcing. A network of > 30 MWRs is currently in operation under the Aerosol Radiative Forcing over India (ARFI) Project of Indian Space Research Organization’s Geosphere Biosphere Program (ISRO-GBP). This paper reports the results of an extensive inter-comparison of the AODs deduced using the MWR with those obtained from other commercially available instruments, such as a Multi-Filter Rotating Shadowband Radiometer (MFRSR), a calibrated Microtops Sun Photometer (MTOPS) and an EKO Sun Photometer (ESP). The results indicated very good agreement between the AOD derived from MWR with MFRSR, MTOPS and ESP with correlation coefficients of ~ 0.99, 0.88 and 0.92, respectively. This report is intended to serve as a reference document for researchers while using the MWR along with other commercial instruments. Page(s): 364-371

Impact of the solar eclipse of 15 January 2010 on the surface ozone and nitrogen dioxide concentrations at Kanyakumari, India

2011-01-21T16:30:28Z

Title: Impact of the solar eclipse of 15 January 2010 on the surface ozone and nitrogen dioxide concentrations at Kanyakumari, India Authors: Elampari, K; Chithambarathanu, T; Jeyakumar, S Johnson; Sharma, R Krishna Abstract: Solar radiation derives the chemistry of the atmosphere. Solar eclipse, being a rare event, provides unique opportunities for studying the changes in the atmosphere due to the sudden reduction in the incoming radiation. The effects of solar eclipse of 15 January 2010 on surface ozone (SOZ) and nitrogen dioxide (NO₂) at the coastal site, Kanyakumari (8^o4’8’’N, 77^o33’6’’E), Tamil Nadu, India, has been investigated in the present study. The behaviour of SOZ, NO₂and variation in meteorological parameters, like temperature, relative humidity (RH) were studied during this annular solar eclipse as well as one day before and after the eclipse. The experimental results showed that solar eclipse phenomenon affects the concentration of SOZ and NO₂ as well as temperature and RH near the ground. Further, few minutes after the total eclipse, SOZ decreased to around 30 ppb, which is 25 ppb less than the normal and the level of nitrogen dioxide increased to 5 ppb. Also, it was noticed that during the course of the eclipse, the RH increased by 3% and temperature decreased by 4°C. The decrease in SOZ concentration was attributed to the reduction in the incoming solar radiation that affects the photochemical reaction. The observed increase in the NO₂ concentration may primarily be due to the low photolysis rate of NO₂. Page(s): 359-363

Ionospheric ion density variation in the low and mid latitude ionosphere: Possible connection with earthquake

2011-01-14T16:30:30Z

Title: Ionospheric ion density variation in the low and mid latitude ionosphere: Possible connection with earthquake Authors: Maheshwari, N; Sharma, D K; Khurana, M S; Rai, Jagdish Abstract: The problem of earthquake prediction has revealed correlation between seismic activity and ionospheric ion temperature and density anomalies. This paper presents observations of the ion density measured with the help of Retarding Potential Analyzer (RPA) payload aboard Indian SROSS-C2 satellite in the altitude ~500 km. The satellite data was analyzed from January 1995 to December 1996 to see the fluctuations in ion density over the seismic region. The emphasis of this paper is on the anomalies in the low and mid latitude ionosphere. The results obtained confirm the earlier results of ion temperature anomalies over the same region. Page(s): 353-358