Jolly Rajendran

Design and Optimization of Band Pass Filter for Software Defined Radio Telescope

Design and optimization of a parallel-coupled microstrip bandpass filter for Software Defined Telescope is presented in this paper. The simulation and optimization is done using ADS and Momentum. The filter is designed and optimized at a center frequency of 1.42GHz. The filter is built on a relatively cheap substrate FR-4 with permittivity 4.4 r   and loss tangent . Simulation results reveal that the filter operation is optimum over the frequency range 1.41 GHz to 1.44 GHz. The 3 dB bandwidth is thus 300 MHz. the return loss is below -10 dB over the passband. Insertion loss is -2.806 dB in the passband. The filter is almost matched to the characteristic impedance ( 0 Z ), 50 Ohms. Also it is observed that the phase varies linearly with frequency. The filter once fabricated could be used at the radio receiver of the Software Radio Telescope to filter out terrestrial radio interference.

Hindi Character Segmentation in Document Images using Level set Methods and Non-linear Diffusion

is the national language of India, spoken by more than 500 million people and is the second most popular spoken language in the world, after Chinese. Digital document imaging is gaining popularity for application to serve at libraries, government offices, banks etc. In this paper, we intend to provide a study on character binarization and segmentation of Hindi document images, which are the essential pre-processing steps in several applications like digitization of historically relevant books. In the case of historical documents, the document image may have stains, may not be readable, the background could be non-uniform and may be faded because of aging. In those cases the task of binarization and segmentation becomes challenging, and it affects the overall accuracy of the system. So these processes should be carried out accurately and efficiently. Here we experiment level set method in combination with diffusion techniques for improving the accuracy of segmentation in document process task. KeywordsSet Method, Binarization, Segmentation, Convex Optimization.

Design and evaluation of printed log periodic dipole antenna for an L band electrically steerable array system

RADAR systems that use a phased array and an electronically scanned array of antennas are extensively used in terrestrial applications on account of their vastly improved directive gain over single-element antennas. The effective beam pattern in such cases is a combination of the elemental pattern and the array factor. In this paper, the design and evaluation of a printed log-periodic dipole antenna, that operates in the L-band, is being discussed. The antenna was fabricated on an FR-4 substrate using printed circuit technology; tested and characterized in terms of its S-parameters, return loss, and insertion loss. The radiation pattern in the azimuth and elevation planes has also been determined. The antenna is found to have a directive pattern, and is linearly polarized with a wide bandwidth. The antenna is being designed for use in the front-end of a RADAR system for terrestrial surveillance applications such as landslide detection, and monitoring the productivity of metallicore mines.

ON THE MINIATURIZATION OF LOG PERIODIC KOCH DIPOLE ANTENNA USING SPLIT RING RESONATORS

In this paper, a printed split ring resonator (SRR) loaded log-periodic Koch dipole antenna (SLPKDA) is proposed. Koch-shaped dipoles when being loaded with split ring resonator (SRR) yielded a compact antenna, still preserving the radiation properties of log-periodic dipole antenna (LPDA). Measurement results show that the proposed antenna has a wide bandwidth, good impedance match and gain of 4 dBi over the band of frequencies from 0.9 GHz to 2.5 GHz. Both vertical and horizontal dimension reductions are achieved by loading Koch dipoles with SRR.

A low-cost compact wideband printed planar Log Periodic Sierpinski Antenna

In this paper, sierpinski-shaped dipoles are introduced in a printed log-periodic dipole antenna design. A Log Periodic Sierpinski Antenna (LPSA) is developed and the characteristics studied. Antenna size is considerably reduced, still maintaining the overall performance characteristics. The results are compared with that of a standard printed LPDA. A set of shapes of LPSA are studied and the observations and characteristics analysed. A size reduction of approximately 50% is achieved by the LPSA when compared with ordinary printed LPDA. The antenna size is reduced considerably with little degradation in the radiation characteristics. This paper proposes two antenna prototypes viz. LPSA and LPS2A operating at L-band and higher frequency range. They are compact compared to the LPDA counterparts. The two antenna prototypes is to be fabricated on cheap FR-4 substrate. Return loss, radiation pattern and gain of the two antenna prototypes are studied. Simulations are carried out in Ansoft HFSS. The antennas are found to have stable radiation pattern. The results are compared with the LPDA counterpart and comparison of performance presented. The simulated results show that the proposed antenna prototypes have better and stable characteristics compared to LPDAs and could be used in L band and S band.

Phased antenna array design for l-band aerospace detection of radiolytic components

In a nuclear accident situation there is a need for a long range stand-off monitoring system, since severe environmental contamination with radioactive nuclides can make in-situ methods hazard prone. In this paper, the design and simulation of phased arrays using log periodic dipole antennas for potential application in the detection of radiolytic components in water, created out of the exposure of the ubiquitous water molecule to gamma radiation is presented. Various configurations like linear and planar array designs were studied. The proposed array designs could be mounted on an unmanned air vehicle, balloon or a satellite to monitor large-scale nuclear incidents. The antenna response and array response were studied in terms of characteristics like system equivalent flux density, sensitivity, gain and polarization. From such studies, a suitability evaluation for the design to detect radiolytic components is performed.

Design and evaluation of printed log periodic dipole antenna for detection of radiolytic components

In this paper, the design, simulation and evaluation of a wide band printed log-periodic dipole antenna array, which could be used to detect the presence of radiolytic components of the ubiquitous water molecule, is presented. The antenna was fabricated on an FR-4 substrate. The design was simulated and the characteristics such as the scattering parameter, VSWR, input impedance, etc. studied over a wide frequency band. The radiation pattern in the azimuth and elevation plane was studied at two different frequencies in the L-band of the microwave spectrum. The antenna has a directive pattern, and shows a linearly polarized response. The antenna could be used to monitor the presence of ionising nuclear radiation that can make the neutral water molecules undergo a breakdown sequence into hydrogen peroxide, hydrogen radicals and assorted oxygen compounds, such as ozone, which when converted back into oxygen releases great amounts of energy. The antenna design shows two resonance peaks that are in the frequencies corresponding to the dissociated components, viz. 1.68 GHz and 1.42 GHz.

Design and simulation of low noise amplifier for RF front end at L band

In this paper, the design and evaluation of a low noise amplifier, that operates in the L-band, is being discussed. The amplifier was fabricated on FR-4 substrate. ATF-58143 Low Noise Enhancement Mode Pseudomorphic High Electron Mobility Transistor [HEMT] is used. The designed LNA is found to have a gain of 13 dB. The return loss is below -10 dB.