NISCAIR Online Periodicals Repository Collection: IJRSP Vol.37(2) [April 2008]

Jovian decametric radio emission: An overview of the planetary radio astronomical observations

Sat, 29 Mar 2008 22:58:59 GMT

Title: Jovian decametric radio emission: An overview of the planetary radio astronomical observations

Authors: Bose, S K; Sarkar, S; Bhattacharyya, A B

Abstract: The paper presents an overview of the Jovian decametric (DAM) radio emission up to the recent years. Evidences for periodic modulation of Jupiter’s DAM radio emission are considered first. Information of Io (Jupiter’s Galilean satellite) and non-Io related source location and their characteristic features of emission, e.g., polarization, shape of the beam, L-bursts, S-bursts, N-bursts, modulation lane etc. are discussed. Broadband electrostatic noise and field aligned current sources at Earth and Jupiter have been taken into account. The scope and direction for further investigations is also pointed out.

Page(s): 77-108

OVSF code groups and reduction in call blocking for WCDMA systems

Sat, 29 Mar 2008 22:58:59 GMT

Title: OVSF code groups and reduction in call blocking for WCDMA systems

Authors: Saini, Davinder S; Bhooshan, Sunil V; Chakravarty, T

Abstract: Compact code assignment (CCA) scheme for wideband CDMA (WCDMA) system has been proposed using Orthogonal Variable Spreading Factor (OVSF) channelization codes. In WCDMA systems, each User Equipment (UE) is given an OVSF code tree. In CCA scheme, the codes in OVSF code tree are divided into groups and the new call is handled by most congested group. The CCA scheme assigns code to the incoming call in the most compact form such that the available capacity after code assignment is least fragmented. This increases call handling capability of the OVSF-CDMA system. Simulation results show that proposed assignment scheme provide performance improvement in terms of reducing new call blocking probability.

Page(s): 143-147

Analysis of a coupled-cavity slow wave structure for a TWT

Sat, 29 Mar 2008 22:58:59 GMT

Title: Analysis of a coupled-cavity slow wave structure for a TWT

Authors: Alaria, M K; Srivastava, V

Abstract: This paper describes an approach of designing a coupled-cavity slow wave structure (CC-SWS) for a high power traveling wave tube (TWT) using HFSS code, which is a 3-D high frequency electromagnetic simulator. The criteria of deciding the initial design parameters of a cavity are first discussed. Method of computing the dispersion and impedance characteristics of the CC-SWS has been discussed. Analysis was carried out for single and double-slot CC-SWS with coupling slots. Mesh size was optimized for speed and maximum accuracy. The CPU time on Pentium-4, 2.66 GHz system with 1 GB RAM was less then 25 min for three or four cavities. Results of HFSS are matched with the experimental results for a C-band coupled cavity SWS and also compared with the results of analytical method.

Page(s): 139-142

Design and development of inclined longitudinal slot rectangular waveguide antenna for LCP and RCP

Sat, 29 Mar 2008 22:58:59 GMT

Title: Design and development of inclined longitudinal slot rectangular waveguide antenna for LCP and RCP

Authors: Satnoor, S K; Vani, R M; Konda, R B; Mulgi, S N; Hunagund, P V

Abstract: One, two and three pairs of inclined longitudinal slots located at the proper place with an appropriate angle on the broader wall of the rectangular waveguide antenna have been presented in this paper. The location of proper placement of slot and its appropriate angle is one where the antenna gives maximum radiation. The slots are placed from the centre of the broader wall leaving equal distance on either side of the rectangular waveguide with an inclination angle of 39° with respect to centre axis to achieve good polarization pattern. These slots have been cut by electro-discharge machine (EDM) and antennas are designed using computer software AutoCAD 2000 for better precision. The experimental observations are carried out at designed frequency of 9.35 GHz, which gives left circular polarization (LCP). These antennas are also tested at below and above the designed frequency, i.e. at 9.3 and 9.4 GHz to study the polarization pattern and found to give right circular polarization (RCP) and LCP, respectively. It is also experimentally observed that these antennas are capable of producing left and right tilt in radiation pattern without deteriorating the impedance of the antenna. Since their VSWR values are well below the allowed value, i.e. < 2 for all the antennas, it implies better impedance matching. These antennas can find application in bistatic radar system of an aircraft. The design concepts of antenna are described and experimental results are discussed.

Page(s): 135-138