NOPR Collection:

Design and analysis of a gap coupled split circular patch with elliptical slot filled with elliptical patch

2010-04-20T16:30:27Z

Title: Design and analysis of a gap coupled split circular patch with elliptical slot filled with elliptical patch Authors: Bhardwaj, Dheeraj; Sharma, Komal; Bhatnagar, D; Sancheti, S; Soni, B Abstract: The paper presents radiation performance of a gap coupled split circular patch with elliptical slot filled with elliptical patch. Initially, a circular elliptical ring slot antenna is taken and it is modified step by step to achieve an end product with desired performance. The performance of designed antenna after each step is presented systematically. The simulated and measured results of proposed antenna are compared with that of a circular elliptical ring slot antenna. The gap between two gap-coupled semi circular elliptical ring structures and the length of major and minor axis of inserted inner elliptical patch are optimized to achieve best performance. It is observed that with proposed modifications in circular patch geometry, impedance bandwidth, gain and radiation efficiency of antenna are improved considerably. The resonance frequency of end product is lower than that of a circular elliptical ring slot antenna which indicates that for achieving identical resonance frequencies from circular elliptical ring slot antenna and modified circular patch geometry, effective patch size of modified antenna must be reduced. The outcome results into a further compact circular patch antenna with much improved performance. Page(s): 107-113

Geomagnetic observations and ionospheric response during storm on 14 April 2006

2010-04-19T16:30:36Z

Title: Geomagnetic observations and ionospheric response during storm on 14 April 2006 Authors: Bakare, N O; Chukwuma, V U; Adekoya, B J Abstract: A study of the intense geomagnetic storm on 14 April 2006 has been done using ionospheric data obtained from ionosonde station located in the American sector. The results indicate appearance of positive storm before the beginning of geomagnetic disturbance in the mid latitudes and occurrence of strong negative phase at the equator. It was observed that magnetospheric process, responsible for Dst decrease, was the enhancement of the plasma sheet and appeared to be caused by the combined effect of large intense proton density at 1400 hrs UT, southward turning of Bz at 1800 hrs UT and enhancement of speed stream at 1400 hrs UT on 13 April. The ionosonde stations located at American sectors are: College (64.9°N), Gakoma (62.4°N), Goose bay (53.3°N), Boulder (40.0°N), Dyess (32.2°N), Eglin AFB (30.4°N) and Puerto Rico (18.5°N). The present results were obtained using critical frequency foF2. The peak height of F2 layer hmF2 showed that the stations had some degree of simultaneity in the depletion of foF2 between 2000 hrs UT on 14 April and 0100 hrs UT on 15 April and that of hmF2 between 1600 and 1900 hrs UT on 15 April. Page(s): 71-79

Dielectric properties of black and red soils at microwave frequency

2010-04-19T16:30:42Z

Title: Dielectric properties of black and red soils at microwave frequency Authors: Chaudhari, H C; Shinde, V J Abstract: The real (ε′) and imaginary (ε′′) parts of the complex dielectric constant (ε*) of soil with varied moisture content have been determined experimentally under laboratory conditions at 9.44 GHz using infinite sample method. The value of ε′ and ε′′ first increases slowly and then rapidly with moisture content. From this data, the ac conductivity and relaxation time are also reported. The result shows the change in electrical properties of soil before and after the addition of water. These results provide basis for using ground penetrating radar or other high frequency electromagnetic sensors in the detection of soil moisture content. Page(s): 103-106

Nowcasting of Yes/No rain situations at a station using soft computing technique to the radar imagery

2010-04-19T16:30:41Z

Title: Nowcasting of Yes/No rain situations at a station using soft computing technique to the radar imagery Authors: Dutta, Devajyoti; Sarma, Diganta Kumar; Konwar, Mahen; Sharma, Sanjay; Viswanathan, G; Gairola, R M; Das, J; Kannan, B A M; Venkateswaralu, S Abstract: A soft computing model for nowcasting of Yes/No rain situations, with a lead time of 2 h, is developed over DWR station at Satish Dhawan Space Centre (SDSD), Shriharikota (13.66°N, 80.23°E) using Doppler weather radar (DWR) reflectivity imageries. Primarily, precipitating systems of mesoscale, i.e. meso-gamma (2-20 km), meso-beta (20-200 km) and meso-alpha (200-2000 km) are considered for the present study. The main components of soft computing approach are: analysis of two-dimensional reflectivity imageries from DWR and utilization of artificial neural network (ANN) for training of input/output data. About 15 input and one output parameters are extracted from radar imageries. The image analysis and training of ANN are carried out on MATLAB platform. After training of ANN, 91 and 77% results are matched with the observed values for No rain and Yes rain situations, respectively. The probability of detection (POD) for the nowcasting of Yes/No rain situations is found to be 0.84. The significant improvement in the nowcasting of Yes/No rain situations is observed by the developed methodology as compared to linear multivariable regression method. The POD of Yes/No rain for other two locations, namely Chennai (12.99°N, 80.18°E) and Tiruvallur (13.09°N, 79.57°E) are found to be 0.81 and 0.77, respectively. Overall, reasonably good results are obtained by the newly developed soft computing model. Page(s): 92-102