G. A. Shanmugha Sundaram

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.

Design of dual log-spiral metamaterial resonator for X-band applications

Dual log-spiral designs that represent inclusions at the elemental level, in the synthesis of metamaterials with negative values of permittivity (ε) and permeability (μ), are analysed for their application in the X band frequency range based on the equivalent circuit model. The dual log-spiral resonator is useful when it comes to miniaturization for relevant applications. The extended LC model focuses on the impact of start angle in coupling factor and mutual inductance values. Estimation of Scattering parameters, bandwidth of operation and impedance of metamaterial samples is performed. Results from full wave simulation tests on this model are used to accurately design miniaturized artificial magnetic inclusion in a homogeneous material so as to have anomalous values of ε and μ. Discussions on the effective role of Artificial Neural Network method as a potent optimization technique in design are also presented.

Efficient use of bandwidth by image compression for vision-based robotic navigation and control

In the present modern world, humans are being replaced by computers in almost every field for various beneficial reasons. One such field, where intervention of computers is inevitable and making significant progress is “computer vision”, which replicates human vision. In computer vision system, similar to that of an eye, a sensor (a camera) is used to capture the images and different algorithms that usually run on a computer acts as brain for analyzing and understanding features in those captured images. Generally, image is visual representation of information. For better analyzing the information that an image has, many image processing techniques are being used. In real, complete view of an area is always challenging. Here, we are achieving monitoring surroundings of a robot by detecting moving objects from a sequence of panoramic stitched images, which is typically a feature extraction problem in computer vision. By knowing the surrounding environment of a robot, we can enhance its navigation and control. A camera setup, which consists of a single camera or multiple cameras, mounted on the robot is used for acquiring about twenty images, each at an angle of 20 degrees, so as to cover entire 360 degrees Images overlapping with the previous image are stitched to get a single panoramic image. Many of such stitched panoramic images can be created for the same scene at different intervals of time and these complete set of stitched images are then processed at the base station for detecting moving objects over that particular scene. So for analyzing the environment by the images acquired, they have to be transferred to the base station by means of a communication channel. Stitching can be done either at the base station or at the on-site. In the earlier case, we need to transfer all the twenty images per interval to the base station but in the latter we just have to send a single stitched image, which reduces the bandwidth usage. Further, using image compression technique for compressing stitched image enhances the efficient usage of channel bandwidth.

SAR image processing using GPU

Synthetic aperture Radar (SAR) has been extensively used for space-borne Earth observations in recent times. In conventional SAR systems analog beamsteering techniques are capable of implementing multiple operational modes, such as the Stripmap, ScanSAR, and Spotlight, to fulfill the different requirements in terms of spatial resolution and coverage. Future RADAR satellites need to resolve the complex issues such as wide area coverage and resolution. Digital beamforming (DBF) is a promising technique to overcome the problems mentioned above. In communication satellites DBF technique is already implemented. This paper discuses the relevance of DBF in space-borne RADAR satellites for enhancements to quality imaging. To implement DBF in SAR, processing of SAR data is an important step. This work focused on processing of Level 1.1 and 1.5 SAR image data. The SAR raw data is computationally intensive to process. To resolve the computation problem, high performance computing (HPC) is necessary. The relevance of HPC for SAR data processing using an off-the-shelf graphical processing unit (GPU) over CPU is discussed in this paper. Quantitative estimates on SAR image processing performance comparisons using both CPU and GPU are also provided as validation for the results.

Optimization of ring parameters of artificial magnetic resonators using Swarm intelligence and Hybrid Genetic Algorithm

Proliferation of wireless technology has made Electromagnetic Compatibility an indispensable field of research. The need for efficient system performance in a dynamic electromagnetic environment calls for accurate design of Electromagnetic shielding devices. Artificial magnetic resonators are miniature structures with negative permeability within a specific band. These resonators act as narrowband absorbers at wavelengths in the order of their dimensions. In this paper, the existing equivalent circuit models are discussed for three kinds of magnetic resonators: Multiple Split Ring Resonator, Spiral Resonator, and Labyrinth Resonator. The dependence of the resonant frequency on multiple geometric parameters of the rings is demonstrated. The design parameters of the rings are optimized using Particle Swarm Optimization (PSO) and the proposed Genetic Algorithm — Constrained Nonlinear Optimization Hybrid. These results have been supported by full wave simulations using Ansoft HFSS.

Panoramic Surveillance Using a Stitched Image Sequence

Security threats have always been a primary concern all over the world. The basic need for surveillance is to track or detect objects of interest over a scene. In most of the fields, computers are replacing humans. One such field where computers play a great role is surveillance. Typically, computer based surveillance is achieved by computer vision that replicates human vision. Here, sequences of panoramic images are created and moving objects are detected over a particular time. Moving objects are being detected using various background subtraction methods like Frame Differencing, Approximate Median and Mixture of Gaussians. In real-time applications like surveillance, the time that takes to make a decision is critical. Hence, a comparison is made between these methods in terms of elapsed time.

FPGA-Based Heavy-Ion Beam Trajectory Estimation and Control for Superconducting RF Cavity Resonator Applications

The manipulation of heavy ion beams by applying fluctuating external electric and magnetic fields is discussed here. The critical beam parameters that are identified with beam trajectory are identified and their properties are discussed. Most of the beam measurements are based on the electromagnetic fields induced by the beam. The analog signals obtained from the sensors are amplified and shaped before they were converted into numerical values, which are then further treated in order to extract meaningful machine parameter measurements. The primary goal is to calculate the ion beam position and degree of spatial coherence. Beam position monitors (BPM) are used for this purpose. The pickup (PU) points were defined to collect the horizontal and vertical difference signals, that in turn were used to calculate the position and trajectory. A system of quadrupoles, modified quadrupoles and octupoles was replacably used for confining and focusing the beam. The BPM readings were modeled based on the readings from simulated ion motion in MATLAB. These results were further processed with noise and digitized and fed into an FPGA implementation of the Kalman filter for estimation of the ion trajectory.

PAM4-Based RADAR Counter-Measures in Hostile Environments

Signal jamming and counter-jamming have become areas of intensive research in the field of radar systems engineering. Either of signaling systems and jamming techniques have had concomitant development. While non-linear frequency modulation (NLFM) signals and polyphase codes continue to be the most preferred radar signals, they still are very much susceptible to jamming, and radars could be easily deceived, given that these signals are predictable in nature. In the work reported here, radar signaling based on 4-level pulse amplitude modulation (PAM4) is considered as an effective modulation scheme to evade jamming, since inclusion of PAM4 in typical pulsed radar signals shows a marked improvement as a function of target detectability. In recent years, PAM4 has gained prominence having had a demonstrable 100+ Gbps of data transmission rate over optical fibers. PAM4 is evaluated against conventional modulation schemes such as NLFM and QAM techniques in terms of burn-through range, cross-over range, and bit error rate. Simulation is done with a multiple-input multiple-output (MIMO) transmit-receive system that are used to replicate a bi-static radar configuration. Various criteria that are typical of a hostile signal environment such as multipath propagation and fading, atmospheric effects, slow fading due to target motion, and also a self-screening jammer are considered for evaluation of performance of PAM4. It is observed that PAM4 performs much better than conventional radar signals in the presence of a jammer signal, thereby indicating its potential as an effective counter-measure in hostile signal environments.

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.

Impact of orbital perturbations on LEO solar power satellite formation in a wireless broadband over power system

Increasing power requirements lead the way for the development of new innovative ideas to generate electricity like the introduction of solar power satellites. This system consists of a number of satellites such that the maximum solar energy is collected. This energy is then converted to electromagnetic beams and transmitted to Earth wirelessly. Simultaneous wireless power and data transmission is performed for better efficiency. There are some external forces which act on the satellite formation, as a result of which they are deviated from their orbit. The orbital elements of the formation and the perturbing forces which they are acted upon are determined. A periodic variation on the orbital elements is observed. The receiver on the Earth station, called the rectenna, is designed to collect both wireless power and data simultaneously. A novel design for the solar power satellite formation in a low earth orbit has been proposed.