NOPR Collection:

A dual-band stacked rectangular microstrip antenna

2010-06-22T16:30:33Z

Title: A dual-band stacked rectangular microstrip antenna Authors: Vishwakarma, Rajesh Kumar; Tiwari, Sanjay Abstract: A dual-band characteristic of stacked rectangular microstrip antenna is experimentally studied. It is a probe fed antenna for impedance matching with 50Ω coaxial cable. This antenna works well in the frequency range 2.86-4.63 GHz. It is basically a low cost, light weight medium gain antenna which is used for mobile communication. The variations of the length and width (1 mm) of the stacked rectangular patch antenna have been done. It is found to have dual resonance with increasing lower resonance frequency and almost constant upper resonance frequency with increases of the length and width of rectangular microstrip antenna. The input impedance and voltage standing wave ratio (VSWR) return loss have been measured with the help of network analyzer. Page(s): 163-169

Single layer modified rectangular microstrip array antenna for multi band and wide band applications

2010-06-26T16:30:27Z

Title: Single layer modified rectangular microstrip array antenna for multi band and wide band applications Authors: Mallikarjun, S L; Hadalgi, P M Abstract: A four-element modified rectangular microstrip array antenna (4MRMSAA) is designed and further extended to eight element modified rectangular microstrip array antenna (8MRMSAA). A comparative study is made between the proposed antennas. The experimental results show that 4MRMSAA operates for multi band and 8MRMSAA operates for wide band with an improvement (39.34%) in impedance bandwidth. This improvement in the impedance bandwidth of 8MRMSAA is 13.80 times more as compared to single rectangular radiating element (RMSA). The experimental results of the proposed antennas have been presented in terms of impedance bandwidth, return loss, gain, half power beam width (HPBW) and cross polarization levels. These multi band and wide band antennas have applications in modern communications and radar communication systems. Page(s): 156-162

Relationship between Dst and solar wind conditions during intense geomagnetic storms

2010-06-24T16:30:30Z

Title: Relationship between Dst and solar wind conditions during intense geomagnetic storms Authors: Bakare, N O; Chukwuma, V U Abstract: A study of 83 geomagnetic storms during 1996-2006 has been carried out to investigate the relationship between Dst and solar wind plasma parameters during intense geomagnetic storms. The geomagnetic storms are primarily associated with two classes of drivers: the magnetic cloud and complex ejecta. It was found that magnetic cloud were drivers in 43 geomagnetic storm (~ 51.8%) while complex ejecta were responsible for 40 geomagnetic storms (~ 48.2%). The correlation between Dst and magnetic field B; and between Dst and Bs was 0.76 and 0.90, respectively for geomagnetic storms resulting from magnetic clouds. The correlation between Dst and B; and between Dst and Bs was 0.71 and 0.64, respectively for geomagnetic storms resulting from complex ejecta. Furthermore, it was shown that the correlation between the Dst and solar wind speed V for magnetic cloud and complex ejecta was 0.58 and 0.57, respectively. It was observed that the correlation between Dst and VBs for magnetic cloud and complex ejecta were 0.77 and 0.71, respectively. The present results suggest that though both classes of drivers can cause intense geomagnetic storm but magnetic cloud is more geo-effective than complex ejecta. Page(s): 150-155

Scattering of VLF signals from localized perturbations in the lower ionosphere

2010-06-25T16:30:27Z

Title: Scattering of VLF signals from localized perturbations in the lower ionosphere Authors: Singh, Vikram; Singh, Birbal Abstract: A wave-slab interaction model has been used to study the scattering of very low frequency (VLF) ground transmitter signals from localized enhancements of ionization in the lower ionosphere caused by transient luminous events (TLEs) such as sprites. The variation of reflection coefficients has been studied for a fixed frequency VLF transmitter signal of frequency 19.8 kHz (NWC, Australia) monitored at Agra for different slab thicknesses, incident angles, and enhancement factors. The results show that sufficient strength of the reflected signals is obtained for a slab thickness of 3 km, enhancement factor between 2.5 and 3, and incident angle around 75⁰. These results explain satisfactorily the VLF amplitude and phase anomalies in sub-ionospheric VLF transmitter signals recorded at Agra station which are interpreted as caused by transient luminous events. Page(s): 144-149