Debalina Ghosh

DESIGN OF A WIDE-ANGLE BICONICAL ANTENNA FOR WIDEBAND COMMUNICATIONS

The wide-angle bicone antenna terminated by a spherical cap is investigated. The antenna radiation patterns have been observed for various values of ka where k represents the phase constant and a represents the conical length. It is seen that for large values of ka the radiation pattern is limited within an angular sector bounded by the cones of the antenna. Next the antenna is optimized for ultra- wideband (UWB) operation through the use of loading techniques. The transient wideband radiated and received responses of the antenna have been observed and the relationship between the wave shapes of the transient fleld and the input pulse have been determined.

Extraction of the signature of a buried object using GPR

This paper deals with the possibility of remotely detecting buried objects using impulse radiating GPR. Most GPR systems involve the B-scan or the C-scan of the ground requiring the usage of advanced imaging techniques. Identification of a buried target is done using only a single snapshot of the ground. An electromagnetic pulse is sent into the ground from a transmitting antenna. The target reflects the pulse and the reflection is received by a receiving antenna. A single temporal scan of the ground is utilized for identification of the target characteristics. The antenna responses are deconvolved out from the receiver response. The deconvolution is carried out by using the conjugate gradient method. Finally, the target response is identified by extracting the natural resonance frequencies by applying the matrix pencil method on the transient waveform. Successful identification of buried targets is achieved through this methodology.

Large array synthesis using Invasive Weed Optimization

This paper discusses the application of nature-inspired optimization techniques for the synthesis of large arrays of antennas. Here the technique of Invasive Weed Optimization (IWO) is chosen for the optimization of the amplitude and/or phase of the excitation at the individual elements of the array. The result of such optimization is performance improvement of the array in terms of minimization of sidelobe levels (SLL) and positioning of nulls at desired locations as compared to the uniformly excited linear array. It is seen that even large arrays of 100 elements can be effectively synthesized using this proposed algorithm.

Constraint-Based Synthesis of Linear Antenna Array Using Modified Invasive Weed Optimization

This paper presents a novel technique for the synthesis of unequally spaced linear antenna array. The modifled Invasive Weed Optimization (IWO) algorithm is applied to optimize the antenna element positions for suppressing peak side lobe level (PSLL) and for achieving nulls in specifled directions. The novelty of the proposed approach is in the application of a constraint-based static penalty function during optimization of the array. The static penalty function is able to put selective pressure on the PSLL, the flrst null beam width (FNBW) or the accurate null positioning as desired by the application at hand lending a high degree of ∞exibility to the synthesis process. Various design examples are considered and the obtained results are validated by comparing with the results obtained using Particle Swarm Optimization (PSO), Ant Colony Optimization (ACO) and Cat Swarm Optimization (CSO). Results demonstrate that the proposed method outperforms the previously published methods in terms of a signiflcant reduction in peak side lobe level while maintaining strong nulls in desired directions. The ∞exibility and ease of implementation of the modifled IWO algorithm in handling the constraints using static penalty function is evident from this analysis, showing the usefulness of the constraint based method in electromagnetic optimization problems.

Design of through-the-earth mine communication system using helical antennas

The helical antenna can be used in through-the-earth mine communications systems. Properly designed the field reaching the receiver above the ground is sufficient for maintaining communication with the underground transmitter.

Synthesis of Thinned Planar Antenna Array Using Multiobjective Normal Mutated Binary Cat Swarm Optimization

The process of thinned antenna array synthesis involves the optimization of a number of mutually conflicting parameters, such as peak sidelobe level, first null beam width, and number of active elements. This necessitates the development of a multiobjective optimization approach which will provide the best compromised solution based on the application at hand. In this paper, a novel multiobjective normal mutated binary cat swarm optimization MO-NMBCSO is developed and proposed for the synthesis of thinned planar antenna arrays. Through this method, a high degree of flexibility is introduced to the realm of thinned array design. A Pareto-optimal front containing all the probable designs is obtained in this process. Targeted solutions may be chosen from the Pareto front to satisfy the different requirements demonstrating the superiority of the proposed approach over multiobjective binary particle swarm optimization method MO-BPSO. A comparative study is carried out to quantify the performance of the two algorithms using two performance metrics.

Adaptation of a novel technique to increase the band width and gain of a Bow-Tie antenna by using frequency selective surface

A microstrip-fed planar Bow-Tie antenna placed above a frequency selective surface with bandwidth and gain enhancement by means of 2×2 array of unit cells acting as AMC is presented here. The electrical characteristics of the integrated design are figured out by using CST MWS. The simulated results in terms of impedance bandwidth and radiation pattern of the Bow-Tie antenna with and without AMC are shown for comparison. The impedance bandwidth and gain of the new antenna are seen to be increased up to 31% and 8dBi respectively.

Comparison of different EBG structures for RCS reduction of patch antenna arrays

This paper describes a novel method for radar cross section (RCS) reduction of patch antenna arrays. Such RCS reduction may be achieved either at in-band or at out-band frequencies depending on the parameters of the EBG unit cell. EBG unit cells are used to cover various proportions of the array substrate and a comparison study is shown for four different models obtained thereby. It is concluded that a model with half the open substrate area covered by the EBG cells gives the best RCS reduction.

A non-dispersive spiral antenna for UWB applications

Broadband antennas are very useful in many applications as they operate over a wide range of frequencies. The objective of this paper is to study the transient response of the spiral antenna over broad frequency ranges. As such, the phase response of the antenna as a function of frequency is of great interest. In the ensuing analysis, the antenna is excited by a monocycle pulse. The antenna has a dispersed output response. This paper deals with ways of converting the resonating spiral antenna to a non-dispersed antenna by using resistive loading. Appropriate loading increases the bandwidth of operation of the antenna. But the drawback is the additional loss in the load applied to the antenna structure, leading to loss of efficiency to around fifty percent.

Cat Swarm Optimization with Normal Mutation for Fast Convergence of Multimodal Functions

Abstract A normal mutation strategy based cat swarm optimization (NMCSO) that features effective global search capabilities with accelerating convergence speed is presented. The classical CSO suffers from the premature convergence and gets easily trapped in the local optima because of the random mutation process. This frailty has restricted wider range of applications of the classical CSO. To overcome the drawbacks, the normal mutation is adopted in the mutation process of this paper. It enables the cats to seek the positions in better directions by avoiding the problem of premature convergence and local optima. Experiments are conducted on several benchmark unimodal, rotated, unrotated and shifted multimodal problems to demonstrate the effectiveness of the proposed method. Furthermore, NMCSO is also applied to solve the large parameter optimization problems. The experimental results illustrate that the proposed method is quite superior to classical CSO, particle swarm optimization (PSO) and some of the state of the art evolutionary algorithms in terms of convergence speed, global optimality, solution accuracy and algorithm reliability.