Shiv Narayan

A Novel EM Analysis of Double-Layered Thick FSS Based on MM-GSM Technique for Radome Applications

The EM analysis of double-layered thick FSS structure with low-loss dielectric medium between the FSS layers has been carried out using MM-GSM technique. In this analysis, both evanescent and propagating modes are included that enhances the accuracy of the computation. This method provides less computational complexity in the formulation of FSS structures as compared to other numerical techniques. The cascaded FSS structure shows bandpass response (> 95% transmission) over a frequency range from 8.84 GHz to 10.74 GHz. It is found that this FSS structure shows very good in-band transmission characteristics and excellent roll characteristics outside the band. Further, the dependence of transmission characteristics on the spacing between the FSS layers is also investigated. The optimum bandpass response is achieved for 0.3

Electromagnetic Techniques and Design Strategies for FSS Structure Applications [Antenna Applications Corner]

Frequency-selective surfaces (FSSs) have a wide spectrum of applications in airborne platforms, wireless communication systems, medical imaging instruments, and high-power microwave systems. To employ finite, electrically large, and conformal FSSs for such applications, the development of an efficient electromagnetic (EM) design and analysis technique is essential, which is a challenging task in terms of computational complexity and requirements of highend computing platforms. In view of assessing the efficacies of various EM techniques for the design and analysis of FSS structures employed for planar and conformal surfaces, a brief review is presented here. Furthermore, the design strategies of novel FSS structures including metamaterial (MTM)-element FSSs are discussed for specific applications such as highperformance radomes, radar absorbing structures (RASs), and antennas. The complex issues associated with the EM design and analysis of FSS structures are also outlined for radomes, RAS, and antennas.

RF leakage radiation from microwave oven for aircraft interior applications

The EM analysis of RF leakage radiation from microwave oven has been carried out using FDTD method in this paper. Here the microwave oven structure is modeled as rectangular cavity. The leakage through the gap between the door and the oven cavity, which is the most probable path of leakage of radiation, is determined using FDTD method. Further, the far-field radiation pattern of microwave oven is computed by the far-field transformation of Huygens equivalent sources using Greens function. It is found that the RF leakage from microwave oven has a characteristic interference far-field pattern.

EM performance analysis of novel double-layer MNG-ENG metamaterial FSS for radome applications

The EM performance analysis of double-layer MNG-ENG metamaterial FSS is presented in this paper using TLTM method. The transmittance and reflectance characteristics are studied for TE polarization at normal incidence. It is found that the proposed metamaterial structure exhibits superior bandpass characteristics over a wide frequency range 1.9-6.6 GHz and band rejection at 9.9 GHz. Further, the tuning of bandpass and band-reject responses are studied by varying the gap between the rings of SRR.

Frequency Selective Surfaces based High Performance Microstrip Antenna

In order to fulfill the growing demand high-performance low RCS antenna in stealth technology, FSS-based antenna is found to be the better candidate. In view of this, the design and analysis of microstrip patch antennas (MPA) loaded with (i) FSS-based HIS (high-impedance surface) ground plane and (ii) FSS-based superstrate are presented in this book with proper formulations and graphical presentations.

FDTD Modeling of EM Field Inside Microwave Cavities

In this book, analysis of electromagnetic (EM) field inside microwave cavities (e.g., oven, autoclave) is presented using finite difference time domain method (FDTD). In this regard, a domestic microwave oven is considered where EM field distribution inside its cavity is determined using FDTD method. Further, the leakage of RF field from the oven door is also estimated at different plane of the door.

Multi-objective bat algorithm tuned optimal FOPID controller for robust aircraft pitch control

Algorithms based on swarm intelligence, to resolve robustness issue for the optimisation problem of the real world applications, like pitch control of an aircraft system, is nowadays common amongst researchers. Bat algorithm is one of the voiced algorithms in todays context. This paper is an explanatory attempt to discuss tuning of fractional order PID and classical PID parameters using bat algorithm for the weighted multi-objective optimisation. The optimised values obtained from the techniques have been implemented for the pitch control of an aircraft system to obtain the desired robust response. In this paper, a mixed sensitivity H∞ problem has been designed and simulated using MATLAB programming. The efficacy of the results has been established compared with other tuning methods. It has been shown that the design of multi-objective bat algorithm tuned fractional order controller gives better results.

Design of airborne radome using Swastika-shaped metamaterial-element based FSS

This paper presents a novel Swastika-shaped metamaterial structure which exhibits metamaterial behavior (μ- and ε-negative) in distinct frequency ranges. The EM analysis of metamaterial (MTM) structure is carried out using transmission line transfer matrix method and validated with full-wave method based software package. The proposed structure is observed to exhibit bandpass frequency selective characteristics with very good transmission efficiency in the frequency range of 8.5 GHz–10.3 GHz. Further, a planar multilayered radome wall configuration is designed which consists of a thick Arlon layer embedded with Swastika-shaped MTM FSS as the middle layer backed by two thin quartz-based laminations on each side. Further, the thickness of radome wall is optimized sector wise in view of airborne radome applications.

EM design of hybrid-element FSS structure for radome application

A monolithic radome wall embedded with novel hybrid-element FSS shows superior electromagnetic performance when compared to conventional monolithic radome. The proposed FSS structure presented in this paper consists of square loop configured with Jerusalem cross. The EM performance analysis of the proposed FSS structure is carried out based on the equivalent circuit model approach. The FSS structure exhibits bandpass response over the frequency range of 9.68–10.45 GHz with very good transmission efficiency at normal incidence. To show the superiority of FSS-radome over conventional radome, its transmission characteristic is compared with that of half wave monolithic radome at 0° and 50° incidence angle. It is observed that the FSS embedded radome exhibits more bandwidth (1.66 GHz) as compared to monolithic radome (0.5 GHz) and also the proposed FSS-radome shows sharp roll-off characteristics which helps in out-of-band RCS reduction. Further a prototype of FSS embedded planar radome is fabricated and measured for proof-of-the-concept.

Novel Swastika-shaped tightly coupled resonator based metamaterial-FSS for radome applications

A novel metamaterial-FSS (frequency selective surface) is designed in this paper based on the theory of tightly coupled resonators for radome applications. The proposed metamaterial unit cell consists of a Swastika-shaped conductor on each side of the substrate which is shorted at the edges by introducing shorting strips. The structure exhibits negative permittivity and permeability behavior at distinct frequency region. The EM analysis of metamaterial-FSS is carried out using transmission line transfer matrix method and validated with the full-wave method. The structure exhibits bandpass characteristic with very high transmission efficiency (>90%) over the frequency range of 10.43–11.43 and sharp roll-off characteristics outside the band as compared to conventional FSS. In view of radome applications, the EM characteristics are further studied at oblique incidence, which is found to show stable EM characteristics w.r.t. angle of incidence and polarizations.