NOPR Collection:

Noise considerations in Gunn integrated rectangular microstrip antenna

2014-01-23T16:35:36Z

Title: Noise considerations in Gunn integrated rectangular microstrip antenna Authors: Nayak, Anjali; Vishvakarma, Babau R Abstract: In the present paper, noise behaviour of the active patch antenna (GaAs Gunn integrated patch and InP Gunn integrated patch) has been theoretically investigated and consequently the noise figure, noise temperature and noise power are calculated as a function of bias voltage. The noise performance of InP Gunn integrated patch is found to be much better than that of the GaAs Gunn integrated patch. Page(s): 148-154

Microstrip array antenna with and without airgap in plasma environment

2014-01-29T16:36:44Z

Title: Microstrip array antenna with and without airgap in plasma environment Authors: Gupta, Anubha; Pourush, P K S Abstract: The present paper explores the important characteristics of an array of 4×4-element planar array of circular patch microstrip antenna (CPMA) designed on RT-duroid substrate(ɛ_r= 2.32) at 1.155 GHz (L-band) for on-board applications in mobile communication through satellite. An airgap is introduced in between the dielectric and the ground plane which improves the bandwidth and maintain the gain of the antenna geometry. This antenna geometry is studied in presence of plasma environment and the effect of generation of electroacoustic waves on the radiation characteristics of the given geometry is determined. For this, a well established linearized hydrodynamic theory and vector wave function technique is used to derive the expression for the field pattern and radiated power by the antenna. The important antenna parameters like radiation conductance, efficiency, directive gain and bandwidth along with radiation patterns are computed and plotted for both plasma as well as for the free space. Page(s): 143-147

Markov chain models for pre-monsoon thunderstorm in Calcutta, India

2014-01-21T16:36:17Z

Title: Markov chain models for pre-monsoon thunderstorm in Calcutta, India Authors: Dasgupta, S; De, U K Abstract: Markov chain models of first, second and third order have been used to provide a probabilistic description of the occurrence of the thunderstorm phenomenon in the pre-monsoon season (March-May) in Calcutta (India). The analysis is based on the relevant data for the 10-year period 1985-94. Use of Akaike’s information criterion (AIC) reveals that the Markov chain of the third order is perhaps the model that describes best the phenomenon. This finding is also supported by actual verification of the fact that the Markov chain of third order simulates the observed data best. Besides, the time independent behaviour of the chain has also been studied with the help of the steady state probabilities. The theoretical values of the mean recurrence time for thunderstorm and fair weather days hence obtained are in close agreement with the observed data. Page(s): 138-142

Ionospheric E-region irregularities during equatorial counter electrojet

2014-01-20T16:36:42Z

Title: Ionospheric E-region irregularities during equatorial counter electrojet Authors: Rastogi, R G; Subbarao, K S V Abstract: The paper describes a coordinated study of the geomagnetic fields at Trivandrum and Alibag, digital vertical incidence ionograms and oblique VH F backscatter radar echoes at Thumba on a day with a large counter electrojet (CEJ) event in the afternoon hours. It is shown that the cusp type of sporadic-E (E_sc), above the normal E-layer continues to descend with time after the start of CEJ up to about 110 km, indicating downward Hall electric field. When the E_sc layer descends to around 110 km, the downward Hall polarization field due to CEJ, acting on the downward gradient of plasma density in the top side of the layer, generates irregularities by the cross-field instability mechanism. These irregularities give the signature of the q-type of sporadic-E (E_sc) on the ionograms and type-2 VHF Doppler spectra of scatter echoes. With continued descent, E_sc disappears and no VHF echoes are recorded. With intensification of CEJ, the eastward streaming velocity of the electrons exceed the ion acoustic velocity and strong type -l echoes are observed on VHF backscatter radar. With the decrease of CEJ even type-2 echoes disappear and no scatter echoes are observed by HF ionosonde or on VHF radar. Page(s): 130-137