Abstract-A novel microstrip antenna with wide bandwidth is presented. Two different radiating elements connected together through a matched section and are embedded on a single layer structure. This new structure offers a dual-band microstrip antenna. By controlling the two resonance frequencies of the two elements, a wide frequency bandwidth of approximately 9% has been achieved. A more bandwidth enhancement, up to 12%, has been achieved by adding two parasitic elements to one element of the proposed antenna. Fabrication and measurement of S 11 for the proposed antenna has been done. The measured results have been compared with the simulated results using commercial software HFSS version-8.0.
In this paper, an efficient lightweight double-layer microwave absorber with impedancematching structure at X-Ku bands was designed, optimized and implemented. First, genetic algorithm (GA) was considered to optimize the thicknesses and material properties for better absorption of the incident electromagnetic wave and reduction of radar cross section (RCS). Next, with the aid of the obtained dielectric and magnetic properties, the microwave absorber was fabricated from magnetodielectric composite materials besides a natural rubber. Finally, the analytical and numerical results were compared with the measurements to check the validity of the design. Experiments showed that the reflection coefficient for each layer backed with a metallic sheet was insufficient; however, for the double layer absorber, the reflectivity measurement values reached up to −28 dB in the case of normal incidence and −17 dB for oblique incidence.
Abstract-In the military applications, electro-optics and electromagnetics features of the cloths made of special textile structures and certain fibers play an important role in producing textile characterized with high ability of camouflage. This means not allowing enemy to precisely determine the moving and mute targets using available radar or any other electro-optics sensors. The aim of this paper is to determine the effect of the composite fabrics structure parameters on the fabrication of a resistive sheet used in many radar applications. The objective sheet can be used as a lossy sheet in absorbing mechanism. The radar absorbing mechanism has been studied with emphasis on the single layer structure mechanism with a resistive sheet. Fabric structure of the resistive sheet was accurately chosen and coated with lossy material. For coating, several formulas of fabrics using carbon black were tested to determine the best chemical treatment in accordance with their functional performance. Lab measurements have been done to get optimum formulas and optimum fabrics structures for high radar absorption performance.
Improving the performance of a microstrip antenna array has been considered based on the innovative use of an absorbing radar cover. Since the surface wave between antennas array elements plays a major role in mutual coupling and scattering behavior of array antenna. The main objective of this work is to reduce the effect of surface wave between array elements using radar absorbing cover. The absorbing cover has been designed with spatial configuration to get maximum performance at the resonant frequency of the fabricated microstrip antenna array. The measured results of the tested antenna array show a significant reduction of both mutual coupling between array patches and radar cross section of the tested antenna array with minimum side effects on the antenna parameters.
Abstract-The most common and simple structure to reduce the level of the reflected power from a metallic surface is the single layer structure known as Salisbury screen which is a sheet of porous material impregnated with graphite and spaced a quarter-wavelength off a metallic backing plate. The main disadvantage of this mechanism is the narrow frequency bandwidth. Many techniques have been reported to improve the working frequency bandwidth but with some degradation in the other technical properties of the overall structure. In this paper a novel technique has been introduced based on a spatial kind of material called circuit analog screen. Theoretical analysis shows that the bandwidth of the reflected power will be improved if the graphite sheet of Salisbury screen has been loaded by circuit analog screen with spatial geometry with spatial parameters.
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