NOPR Collection:

Design and development of complementary-symmetry microstrip antenna for broadband and high gain operation

2011-06-07T16:30:39Z

Title: Design and development of complementary-symmetry microstrip antenna for broadband and high gain operation Authors: Sameena, N M; Mulgi, S N Abstract: A novel design of complementary-symmetry microstrip antenna (CSM) is presented for triple band operation. The triple bands are merged together by embedding a H-shaped slot on the ground plane of CSM which gives maximum impedance bandwidth of 57.66% and a gain of 6.53 dB. The design concept of antennas and experimental results are presented. The proposed antenna may find applications in WLAN systems. Page(s): 166-170

Frequency switching of electrically small patch antenna using metamaterial loading

2011-06-09T16:30:34Z

Title: Frequency switching of electrically small patch antenna using metamaterial loading Authors: Joshi, J G; Pattnaik, Shyam S; Devi, S; Lohokare, M R Abstract: A frequency switchable planar metamaterial loaded electrically small microstrip patch antenna, capable of resonating at different frequencies by varying the loading distance, has been presented in this paper. The rectangular microstrip patch antenna is loaded with planar metamaterial square spilt ring resonators (SRRs) in three different configurations at a distance of 0.25, 0.50 and 0.75 mm, respectively to get the switchable resonant frequency performance. The square SRRs reveals negative permeability () presenting the single negative metamaterial (SNG) characteristics. The unloaded rectangular microstrip patch antenna resonates at 23 GHz. In loading condition at different distances, the rectangular microstrip patch antenna resonates at 9.61, 9.51 and 9.41 GHz, respectively. Using Chu limit, size of the antenna, that is ka, reaches 0.766, 0.775 and 0.787 in respective configurations, thus, satisfies the condition ka <1 for electrically small antenna. The resonant frequency of rectangular microstrip patch antenna decreases with respect to the loading distance due to magnetic coupling. As the loading distance gets reduced, the mutual inductance increases resulting in enhancement of the bandwidth of the antenna. In these three loading conditions, the radiation quality factor (Q_rad)is larger than the minimum Q that is Q_chu. The directivity is more than 7.50 dBi in the presented configurations of electrically small rectangular microstrip patch antenna. Page(s): 159-165

Variability of dielectric constant of saline water in combination with diesel in Cj band (5.3 GHz) and Ku band (13.4 GHz)

2011-06-07T16:30:36Z

Title: Variability of dielectric constant of saline water in combination with diesel in Cj band (5.3 GHz) and Ku band (13.4 GHz) Authors: Calla, O P N; Hasan, Sayeh; Ahmadian, Nima Abstract: In this paper, an attempt has been made to study the variability of dielectric constant of water contaminated by diesel at two different frequencies. The water samples with the salinity range of 5-50 kppm in an interval of 5 kppm have been measured. The weight percentage of diesel in water is from 0 to 280 percent with 20% interval in Cj band and 0 to 160 percent with 20% interval in Ku band. A simple, practical method of extracting the dielectric constant of water contaminated by diesel is presented in Cj band (5.3 GHz) and Ku band (13.4 GHz) with the help of waveguide cell with shift in minima method. It is concluded that the range of dielectric constant of water in combination with diesel in Cj band is wider as compared to Ku band. Moreover, the dielectric constant of water in combination with diesel is greater and differentiation of data was clearer in Cj band when compared to Ku band. Page(s): 153-158

Influence of boundary layer dynamics on pollutant concentrations over urban region – A study using ground based measurements

2011-06-10T16:30:33Z

Title: Influence of boundary layer dynamics on pollutant concentrations over urban region – A study using ground based measurements Authors: Mahalakshmi, D V; Badarinath, K V S; Naidu, C V Abstract: Ventilation coefficient (VC) over urban area of Hyderabad, India during night-time in 2008 has been calculated using night-time mixed layer height with boundary layer lidar (BLL) and radiosonde data to investigate the influence of VC on pollutant concentration. Carbon monoxide (CO), ozone (O₃) and black carbon (BC) aerosol mass concentrations in relation to mixed layer height and wind speed have been analysed for different seasons, viz. winter, pre-monsoon, monsoon and post-monsoon associated with boundary layer and ventilation coefficient (VC). The results of the study suggested that VC plays an important role in dispersing the pollutants. Page(s): 147-152