Sachendra N. Sinha

A Self-Affine Fractal Multiband Antenna

The design of a new fractal multiband antenna based on the self-affinity property is presented in this letter. Experimental return loss has been compared with that obtained using the method of moments and the fractal antenna is found to possess predictable multiband characteristics

Radiation from a waveguide-backed aperture in an infinite ground plane in the presence of a thin conducting plate

Coupled integrodifferential equations are formulated for the general problem of radiation from a waveguide-backed aperture in an infinite conducting plane when a thin, finite, and arbitrarily oriented conducting plate is located in its proximity. The general equations are particularized for the special case of a rectangular aperture and a rectangular plate and solved numerically using the method of moments. Detailed data are presented and discussed for various quantities of interest.

Null steering in failed antenna arrays

Antenna array pattern nulling is desirable in order to suppress the interfering signals. But in large antenna arrays, there is always a possibility of failure of some elements, which may degrade the radiation pattern with an increase in side lobe level (SLL) and removal of the nulls from desired position. In this paper a correction procedure is introduced based on Particle Swarm Optimization (PSO) which maintains the nulling performance of the failed antenna array. Considering the faulty elements as nonradiating elements, PSO reoptimizes the weights of the remaining radiating elements to reshape the pattern. Simulation results for a Chebyshev array with imposed single, multiple, and broad nulls with failed antenna array are presented.

Design of custom-made stacked patch antennas: a machine learning approach

Machine learning approaches, viz. particle swarm optimization in conjunction with neural networks have been used to develop a user friendly tool to design custom-made stacked patch antennas in the entire X-Ku band for satellite communication application. The role of the neural network is to develop a black-box model to relate the frequencies of operation of the antenna with its dimensional parameters. This trained neural network was embedded in the loop of a particle swarm optimizer to decide the design dimensions required for specific user defined frequencies. The effectiveness and accuracy of the developed model are verified by simulations and experimental measurements.

Electromagnetic Transmission through Fractal Apertures in Infinite Conducting Screen

Fractals contain an infinite number of scaled copies of a starting geometry. Due to this fundamental property, they offer multiband characteristics and can be used for miniaturization of antenna structures. In this paper, electromagnetic transmission through fractal shaped apertures in an infinite conducting screen has been investigated for a number of fractal geometries like Sierpinski gasket, Sierpinski carpet, Koch curve, Hilbert Curve and Minkowski fractal. Equivalence principle and image theory are applied to obtain an operator equation in terms of equivalent surface magnetic current over the aperture surface. The operator equation is then solved using method of moments (MoM) with the aperture surface modeled using triangular patches. Numerical results are presented in terms of transmission coefficient and transmission cross-section for both parallel and perpendicular polarizations of incident plane wave which show the existence of multiple transmission bands.

Analysis of coaxial fed dual patch multilayer x/ku band antenna using artificial neural networks

This paper deals with the analysis of stacked patch antenna using neural network techniques. A trained neural network was developed to locate the operational frequency bands of stacked microstrip antenna with two radiating patches, operating in the x/ku band for satellite communication application. The network takes the different design parameters of the antenna as inputs and delivers the upper and lower resonant frequencies. The validity of the network is tested with the simulations from IE3D.

Analysis of Multiple-Strip Discontinuity in a Rectangular Waveguide

The paper considers the problem of an arbitrary number of thin, transverse, and metallic strips Iocated in the cross section of a rectangular waveguide. The strips can either be inductive or capacitive and are arbitrarily located. Equivalence theorem is utilized, in conjunction with appropriate boundary conditions, to set up an integral equation which is then solved using the method of moments. The method is applied to a number of test problems and the numerical results show good agreement with the available data.

A Patch-Loaded Ring-Slot Antenna for Wide Band Circular Polarization

In this paper, a patch-loaded ring-slot antenna is proposed for wide band circular polarization operation. The design methodology is presented. As an example, an antenna operating at 2.4 GHz is designed and optimized according to the established procedure. The performance of the fabricated prototype is in close agreement with the simulated results. The measured impedance bandwidth is around 31% with a peak gain of 7.5 dBic. A 3 dB axial ratio bandwidth of about 22.5% has been achieved.

RADIATION FROM CAVITY-BACKED FRACTAL APERTURE ANTENNAS

This paper investigates the properties of probe fed cavity- backed fractal aperture antennas. The problem is formulated using the flnite element-boundary integral (FE-BI) method in which the fleld inside the cavity is formulated using the flnite element method, and the mesh is truncated at cavity aperture surface using the boundary integral method. Several dual-band cavity-backed fractal aperture antennas based on Sierpinski gasket, Sierpinski carpet, plus shape fractal and Minkowski fractal are investigated. The numerical results obtained from the FE-BI code have been validated with simulations on HFSS.

UWB fractal slot antenna designs

The allocation of 3.1–10.6 GHz spectrum by Federal Communications Commission (FCC) for Ultra Wideband (UWB) radio applications has presented a myriad of exciting opportunities and challenges for design in the communications arena, including antenna design. The challenge of designing compact antennas with operating bandwidths of more than 100% can be met by using wide slot antennas with fractal boundaries. In this paper, two fractal slot antenna designs based upon Koch Snowflake geometry and Sierpinski gasket are presented which have good radiation efficiency over the UWB frequency range. Coplanar waveguide feeds with tuning U-stubs have been used to achieve the desired bandwidth. Optimization of antenna geometries has been carried out with HFSS simulations. The resulting geometry is compact and the measured results compare well with the simulation data.