Anuj Y. Modi

Predicting the Performance of Pyramidal and Corrugated Horn Antennas Using ANFIS

This letter presents the development of an adaptive neuro fuzzy inference system (ANFIS)-based model for predicting the performance of a pyramidal and a conical corrugated horn antennas. Different ANFIS-based models were developed. Using these models, horn return-loss characteristics and radiation patterns (copolarization and cross-polarization) can be obtained with great accuracy for any combination of design parameters. The results obtained using ANFIS models were compared to that of the commercial horn antenna design software and found in close agreement. The advantage of the proposed method lies with the fact that, with less time and minimum computational resources, the return-loss and radiation characteristics of a horn antenna under test can be obtained with high degree of accuracy.

Novel Design of Ultrabroadband Radar Cross Section Reduction Surfaces Using Artificial Magnetic Conductors

A novel technique for designing ultrabroadband radar cross section (RCS) reduction surfaces using artificial magnetic conductors (AMCs) is proposed in this paper. This technique overcomes the fundamental limitation of the conventional checkerboard design where the reflection phase difference of (180±37)° is required to achieve 10-dB RCS reduction. Initially, a planar surface for broadband RCS reduction is designed with two properly selected AMCs in a blended checkerboard architecture. A 10-dB RCS reduction is observed for more than 83% of the bandwidth (3.9–9.45 GHz) with this blended checkerboard design. After modifying the blended checkerboard design using the proposed novel technique, the 10-dB RCS reduction bandwidth increased to 91% fractional bandwidth (3.75–10 GHz) as the criteria of (180 ± 37)° reflection phase difference is no longer required. Measured data show an excellent agreement between the predicted, simulated, and measured data. Bistatic performance of the surface at various frequencies is also presented. Key steps for designing ultrabroadband RCS reduction checkerboard surface are summarized.

Novel design of ultra wideband vertical slotted triangular (VST) sheet antenna

In this paper, a new design of Ultra Wide Band (UWB) antenna is proposed. The antenna parameters in frequency domain analysis have been investigated to show its capability as an effective radiating element. The voltage standing wave ratio is less than 2 (VSWR<; 2) and return loss (S11) is less than -10 dB along the operation bandwidth of 4 GHz to 17 GHz. The simulated return loss, VSWR, input impedance and radiation pattern are presented in this paper. The antenna is very useful for impulse and UWB communication systems (in radar communication, for military application (defense department), bio-medical technology, space communication through satellite) and as proposed antenna has end fire radiation pattern it is very useful in point to point communication with very high gain performance.

Novel technique for enhancing RCS reduction bandwidth of checkerboard surfaces

A new technique for enhancing the RCS reduction bandwidth of checkerboard surfaces is developed. In the conventional checkerboard surface the phase difference of (180 ± 37)° has to be obeyed. Using the proposed technique, this limitation of conventional checkerboard surface has been eliminated, allows extension in 10-dB RCS reduction bandwidth. This design has been implemented on one such conventional broad checkerboard surface. For a designed surface, using the pro technique, the 10-dB RCS reduction bandwidth is increased 83% to 91% (an +8%). Simulated results are included indicate excellent agreement with measurement.

A Novel Design of Directive Ultra Wide Band (UWB) Triangular Sheet Antenna

In this paper, a new design for an Ultra Wide Band (UWB) antenna is proposed. The frequency domain analysis of the projected antenna has been probed to show its capability as an operative element to be used for UWB purposes. The return loss (S11) is less than-10 dB along the operational bandwidth of 3 GHz to 20 GHz (147% fractional bandwidth). In this paper, The simulated return loss, input impedance and radiation pattern are presented and it has been shown that proposed antenna is very useful for impulse and UWB communication systems (in radar communication, for military application, bio-medical technology, space communication through satellite etc.). As the proposed antenna has an end fire radiation pattern it is very useful in point to point communication with very high gain performance.

A novel design of ultra wideband Slotted Vertical Semi Elliptical Sheet Antenna

The paper presents a new UWB antenna named as Slotted Vertical Semi Elliptical Sheet Antenna. The simulated return loss, VSWR, input impedance and radiation pattern are discussed in this paper. The results show that the voltage standing wave ratio is less than 2 (VSWR< 2) and return loss (S11) is less than −10 dB along the operation bandwidth of 4.1 GHz to 12.5 GHz. The asymmetry in the feed position results in increase of the band width but degrades the radiation pattern. However, the radiation pattern can be made directional using an appropriate reflector. The simulated radiation patterns after adding a reflector have also been discussed in the paper.

AMC cells for broadband RCS reduction checkerboard surfaces

A new design approach on selection of AMC structures for designing broadband checkerboard surface is proposed. Using the same approach for checkerboard surface, two basic but properly designed AMC structures are used to achieve broadband RCS reduction, where phase difference of (180 ± 37)° is maintained from 3.6 GHz to 9.4 GHz. The RCS is reduced by more than 10 dB over an 83% fractional bandwidth (3.85–9.3 GHz). A prototype of the finitely sized (2 × 2) checkerboard was simulated and measured. The results show excellent agreement with the predictions.

Cylindrically Curved Checkerboard Surfaces for Radar Cross-Section Reduction

Checkerboard surfaces, for radar cross-section (RCS) reduction, utilizing artificial magnetic conductor structures on flexible cylindrically curved ground planes are introduced. The RCSs of cylindrical checkerboard surfaces are examined for two different radii of curvature. Wideband curved checkerboard surfaces are evaluated under normal incidence for HH and VV polarizations. Simulated bistatic RCS patterns of the cylindrical checkerboard surfaces are presented, discussed, and justified, and the backscattering is compared with measurements. A very good agreement is observed.

PEC-PMC Baffle Inside Circular Cross Section Waveguide for Reduction of Cut-Off Frequency

A design and position of a baffle placed inside a circular waveguide is presented which leads to the lowest possible cutoff frequency. The reduction in the cutoff frequency is achieved by having one side of the baffle be PEC while the other is PMC. The introduction of PMC boundary conditions leads to unique eigenvalues for the dominant mode resulting in 66% reduction in the cutoff frequency compared to that of a circular waveguide with a baffle with PEC surfaces on both sides and 41.7% reduction in the cutoff frequency compared to that of an empty waveguide. An ejωt time convention is used.

Synthesis of Elliptical Patch Micro-strip Antenna using artificial neural network

This paper presents a Neural Network model for the design of an Elliptical Patch Micro-strip Antenna (EPMSA) for a desired frequency in L Band. The artificial neural network (ANN) has been trained in such a way that for any desired gain at any desired frequency in L-band it can generate design parameters of EPMSA with great accuracy. In most of the existing ANNs for the synthesis of EPMSA do not include gain at resonant frequency as it is very difficult to achieve accurate result for it. The main benefit of the proposed method lies with the fact that the various parameters required for the design of an EPMSA at a particular frequency and gain of interest can be easily extracted without going into the rigorous time consuming, iterative design procedures using a costly software package.