Indian Journal of Radio & Space Physics

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(CODEN : IJRSAK        ISSN : 0367-8393)

VOLUME 37

NUMBER 2

APRIL 2008

 

CONTENTS

 

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

77

        S K Bose, S Sarkar & A B Bhattacharyya*

 

 

A study on heating of the lower ionosphere during lightning

109

        S S De*, S K Adhikari, M De, B Bandyapadhyay, A Guha, Suman Paul & B K De

 

 

The finite element approach for evaluation of extinction cross-section of realistically distorted raindrops

 

114

        Amarjit & R P S Gangwar*

 

 

Concentrations of surface O3, NO2 and CO during winter seasons at a semi-arid region – Agra, India

121

        Renuka Saini, G S Satsangi & Ajay Taneja*

 

 

Interaction of electromagnetic radiation with human body

131

        Vijay Kumar*, R P Vats, Sachin Goyal, Sandeep Kumar & P P Pathak

 

 

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

 

135

        S K Satnoor, R M Vani, R B Konda, S N Mulgi & P V Hunagund*

 

 

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

139

        M K Alaria* & V Srivastava

 

 

OVSF code groups and reduction in call blocking for WCDMA systems

143

        Davinder S Saini*, Sunil V Bhooshan & T Chakravarty

 

__________

 

*Authors for correspondence

 

 

 

 

 

Indian Journal of Radio & Space Physics

Vol. 37, April 2008, pp. 77-108

 

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

 

S K Bose1,2, S Sarkar1 & A B Bhattacharyya1

1Department of Physics, University of Kalyani, Kalyani 741 235, WB,India

2Department of Physics, Kalyani Govt. Engineering College, Kalyani 741 235, WB, India

Received 25 August 2005; accepted 5 November 2007

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.

Keywords: Jovian planet, Decametric radio emission, L-bursts, S-bursts, N-bursts

PACS No: 96.30.Kf, 95.85.Bh

 

 

Indian Journal of Radio & Space Physics

Vol. 37, April 2008, pp. 109-113

 

A study on heating of the lower ionosphere during lightning

S S De1, S K Adhikari1, M De1 & B Bandyapadhyay1

and

A Guha1, Suman Paul1 & B K De2

1Centre of Advanced Study in Radiophysics & Electronics, University of Calcutta, Kolkata 700 009, India

2Department of Physics, Tripura University, Suriyamaninagar 799 130, West Tripura, India

E-mail: de_syam_sundar@yahoo.co.in

Received 30 January 2007; revised 26 October 2007; accepted 19 February 2008

Heating of the ionosphere due to incidence of electromagnetic pulses coming from lightning discharges has been theoretically investigated. The electromagnetic radiation from lightning discharges produces variation in ionizing frequency and effective collision frequency of electrons. The energy gained by the free electrons from the incident electric fields of wide-band electromagnetic pulses from lightning strikes is not instantaneously transferred to the heavy particles in the medium, due to which the electron temperature is raised. Variation of temperature increase has been estimated.

Keywords: Lightning discharge, Ionospheric heating

PACS No.: 92.60.Ta; 92.70j

 

Indian Journal of Radio & Space Physics

Vol. 37, April 2008, pp. 114-120

 

The finite element approach for evaluation of extinction cross-section of realistically distorted raindrops

 

Amarjit & R P S Gangwar

Department of Electronics and Communication Engineering, College of Technology, G B Pant University of Agriculture and Technology, Pantnagar 263 145, Uttarakhand, India

Received 5 April 2007; revised 7 December 2007; accepted 21 February 2008

Evaluation of extinction cross-sections (ECS) of realistically distorted raindrop is carried out by using finite element method (FEM) on modified Pruppacher-and-Pitter (MPP) raindrop model for horizontal and vertical polarizations in centimeter and millimeter wave frequency range with mean raindrop radii from 0.025 to 0.35 cm. The results obtained from FEM are compared with existing models based on first order perturbation evaluation technique (FOPET) and volume integral equation formulation (VIEF) using MPP. The results obtained are in good agreement with the results of these models with 6% mean variation in horizontal polarization for both the models and 7% and 10% mean variations are observed in vertical polarization in these models respectively.

Keywords: Raindrop models, Extinction cross-section, Centimeter wave propagation, Millimeter wave propagation, Finite element method

PACS No.: 92.60.Ta

 

 

Indian Journal of Radio & Space Physics

Vol. 37, April 2008, pp. 121-130

 

Concentrations of surface O3, NO2 and CO during winter seasons at
a semi-arid region – Agra, India

 

Renuka Saini, G S Satsangi & Ajay Taneja

School of Chemical Sciences, Department of Chemistry, St. John’s College, Agra 282 002, India

(E-mail: ataneja5@hotmail.com)

Received 6 March 2006; revised 20 February 2008; accepted 22 February 2008

Surface measurements of O3 (ozone) and its precursor gases such as NO2 and CO have been made over an urban site of Agra (semi-arid region). Ozone and NO2 show diurnal variations to an urban site during winter season. The overall increase of ozone is attributed to the increase in NO2, CO and other precursor’s emissions by different sources in the proximity of both the sites, i.e. St. John’s College (SJC) and Dayalbagh. The average concentration of ozone was found to be 27.3 ppbv and it ranges from 1.2 to 69.0 ppbv, whereas the average concentration of NO2 and CO were 66.3 ± 7.0 ppbv and 710.3 ± 159.4 ppbv, respectively. The coefficient of determination of regression curve between O3 and NO2 were r = 0.50 at SJC and r = 0.68 at Dayalbagh, whereas correlation between O3 and CO were r = 0.75 at SJC and r = 0.50 at Dayalbagh, indicating positive correlation. Air samples from the two different locations of Agra city have indicated that the concentrations of ozone and CO were within the permissible limits but NO2 concentration was above the limit.

Keywords: Ozone, Precursor gases, NO2, CO, Photochemical production, Semi-arid region

PACS No.: 92.60.Sz, 82.33.Tb

 

 

Indian Journal of Radio & Space Physics

Vol. 37, April 2008, pp. 131-134

 

Interaction of electromagnetic radiation with human body

Vijay Kumar

Department of Physics, Sushila Devi Bansal College of Technology, Indore 452 012 (MP), India

E-mail: vijay_phd05@rediffmail.com

and

R P Vats & Sachin Goyal

Department of Physics, M S College, Saharanpur 247 001 (UP), India

and

Sandeep Kumar & P P Pathak

Department of Physics, Gurukula Kangri University, Haridwar 249 404 (UA), India

Received 29 December 2005; revised 11 June 2007; accepted 26 February 2008

Whole body specific absorption rate (SAR) is calculated for different frequencies as a function of distance from transmission tower. Comparing with safe limits of exposure as standardized by different international agencies, safe distance of residence from transmission tower is determined. The SAR for fat at a distance of 10, 20, 30, 40, 50 and 60 m is found to be harmful for 27.12-10000 MHz, above 100, 1500, 5000, 8000 and 10,000 MHz, respectively. Harmful range for cortical bone, spongy bone and skeletal muscle is also calculated.

Keywords: Electromagnetic radiation (EMR), Induced electric field, Human body, Specific absorption rate (SAR)

PACS No.: 84.40. Us

 

 

Indian Journal of Radio & Space Physics

Vol. 37, April 2008, pp. 135-138

 

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

S K Satnoor, R M Vani*, R B Konda, S N Mulgi & P V Hunagund

Department of PG Studies and Research in Applied Electronics, Gulbarga University, Gulbarga 585 106, Karnataka, India

*University Science Instrumentation Center, Gulbarga University, Gulbarga 585 106, Karnataka, India

Received 6 September 2006; revised 26 February 2007; accepted 12 February 2008

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.

Keywords: Waveguide antenna, Inclined slot antenna, Polarization, Rectangular waveguide antenna

PACS No.: 84.40.Ba; 84.40.Az

 

 

Indian Journal of Radio & Space Physics

Vol. 37, April 2008, pp. 139-142

 

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

M K Alaria & V Srivastava

Microwave Tubes Area, Central Electronics Engineering Research Institute, Pilani 333 031, Rajasthan, India

Email: mukesh_pilani@yahoo.co.in & vs@ceeri.res.in

Received 20 November 2006; revised 28 June 2007; accepted 14 February 2008

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.

Keywords:   Dispersion, Coupled-cavity slow-wave structures (CC-SWS), Traveling wave tube, Staggered structure, Coupling slots

PACS No.: 84.40.De

 

 

Indian Journal of Radio & Space Physics

Vol 37, April 2008, pp. 143-147

 

OVSF code groups and reduction in call blocking for WCDMA systems

Davinder S Saini, Sunil V Bhooshan & T Chakravarty

Department of Electronics and Communication Engineering, Jaypee University of Information Technology,
Waknaghat, Solan 173 215 (HP), INDIA

davinder.saini@juit.ac.in, sunil.bhooshan@juit.ac.in and tapchak@vsnl.net

Received 26 December 2006; revised 1 October 2007; accepted 18 February 2008

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.

Keywords: WCDMA, OVSF codes, Spreading factor (SF), Code blocking, Code (channel) assignment, Code (channel) reassignment

PACS No.: 84.40.Ua