Alfredo Gomes Neto

Analysis of quasi-square open ring frequency selective surface using the Wave Concept Iterative Procedure

This work presents the analysis of quasi-square open ring frequency selective surface, FSS, using the Wave Concept Iterative Procedure, WCIP. As this structure presents a strongly dependence of the electric field polarization, different frequency bands can be selected. Furthermore, there is a coupled strips region and its length can be used for frequency adjustment. The behavior of the electric fields and how it can affect the resonant frequency is discussed. Numerical and measured results for the frequency of resonance are compared and a good agreement is observed.

Study of the geometric complexity reduction of a quasi-fractal FSS using WCIP

This work presents a design procedure for a simplified geometric quasi-fractal FSS, that starts with the analysis of the effect of several geometry details (small gaps) on the frequency behavior. Firstly FSS structures are numerically analyzed, using the Wave Concept Iterative Procedure (WCIP). Secondly they are experimentally characterized. Thereafter a comparison between simulated and measured results is performed, as well as an investigation of the effect of the FSS geometry on the resonant frequency using the electric and magnetic field distributions, the latter through the electrical current density vector.

Frequency selective surfaces with non fractal geometry

The use of FSS with non fractal geometry is proposed in this work. When non fractal details are applied to rectangular patch, the FSS frequency response can be drastically affected. The frequency of resonance can be reduced and new resonance can be obtained. Furthermore, the bandwidth between resonances can be modified. Then, these characteristics can be utilized to design FSS with multiband operations or to reduce the FSS dimensions. In this work, numerical results, obtained using the WCIP method, are presented and discussed to different FSS with non fractal geometry. Two FSS with non fractal geometry are characterized experimentally and the obtained results compared to numerical ones. The results indicate the potential of the non fractal geometry in the FSS design, which instigate the research for new applications.

Analysis of FSS with Koch Island patch elements using the wave concept iterative procedure

Computer programs for simulation of microwave structures are becoming accessible. However, to understand electromagnetic fields behavior and to comprehend the numerical model limitations, a solid theoretical basis and computational expertise to enable the implementation of the own programs remains indispensable. The wave concept iterative procedure, WCIP, is a numerical technique easy to understand, that can be implemented without great efforts. In this work the WCIP is applied to analysis of frequency selective surface, FSS, with Koch Island patch elements. Obtained numerical results are compared to others obtained by the use of Ansoft Designer™ software and to experimental ones.

Analysis of tapered micostrip patch antenna by the Wave Concept Iterative Procedure

This work presents the analysis of the tapered microstrip patch antenna by the Wave Concept Iterative Procedure, WCIP. The resonant frequencies variation with the patch dimensions and how to include it as project flexibility is discussed. The behavior of the electric fields is presented and analyzed for the first two resonant frequencies. Numerical and measured results are compared and a good agreement is observed.

Analysis of U-slot rectangular patch FSS

This paper reports the analysis of U-slot rectangular patch FSS. The numerical results were obtained using the Wave Concept Iterative Procedure, WCIP. Initially, a conventional rectangular patch is considered and after a single slot is inserted. Then, the U-slot arms are increased and the frequency behavior discussed. In order to validate the numerical results, three FSS were selected, fabricated and experimentally characterized. When compared to simulations, the experimental results present a very good agreement. Considering conventional rectangular patch, the reduction of first frequency of resonance achieve up 63.2%. The proposed FSS frequency behavior may be suitable in the design of multiband structures. In addition, the reduction of the first frequency of resonance also implies miniaturization advantages. These characteristics instigates other research groups to pursuit this investigation.

Four arms star: An useful geometry for switchable FSS

In this paper, the four arms star geometry is proposed as a basic FSS element. The design of the proposed geometry is described and simulated results obtained using the Method of Moments are presented. When compared to the conventional rectangular patch, the four arms star FSS presented a considerable reduction of the first frequency of resonance and values about 50% can be achieve without further optimizations. In addition, the proposed geometry is useful to switchable FSS, because the switch point is limited to a small area, which can avoid undesirable effects, such as parasitic capacitances. The ON-OFF switch states were ideally simulated and the well-defined ON-OFF switch states were observed. In order to validate the numerical results, three FSS were selected, fabricated and experimentally characterized. For each one, the ON-OFF switch state was considered. The obtained experimental results present a very good agreement when compared to simulated ones and confirm the expected frequency behavior. The four arms star FSS performance become very attractive to many applications in modern communications systems, especially smart antennas.

Some experimental results for the head/hand effects in personal communications

In this work, some experimental results for the head/hand effects in personal communications are presented, for the real situation of a person during a call in the AMPS system. The hand-held unit has a monopole antenna. A simple measurement procedure is described and experimental results are discussed including biological effect aspects and wireless communication system performance. The experimental procedure and obtained results instigate other researchers to persue a better characterization of the head/hand-handset interaction in personal communication systems.

Analysis of the resonant behavior of FSS using matryoshka geometry

In this paper the resonant behavior of frequency selective surfaces, FSS, using matryoshka geometry is analyzed considering polarizations x and y. The basics of the FSS using matryoshka geometry are described for usual and open cases, including an expression to estimate the first resonant frequency. Initially, the FSS with two concentric square rings is considered and its resonant behavior analyzed. Then, the resonant behavior of FSS with two rings matryoshka geometry is examined. The analysis is based on the electric current distribution obtained using the commercial software ANSYS-Designer. With a better understanding of the resonance nature in matryoshka geometry the design parameters can be better adjusted and desired frequency responses properly achieved.

Characterization of dual band and double polarized notched metallic ring FSS and their equivalent parallel metallic strip structures

ABSTRACT In this work three rejecting band filters for multi band and dual polarization applications are proposed. The first proposed structure is an open quasi square FSS with a centered notch. The variation of the notch position to the left leads to the tenability of frequencies in both directions of polarization. The addition of a second notch has resulted in a third frequency in the y direction maintaining two resonant frequencies in the x direction. The structures are simulated by the Wave concept Iterative Method and the Comsol Multiphysics software 4.3b. In the second part of this paper a new approach is proposed to obtain an equivalent FSS structures based on non-coupled parallel metallic strips. The new equivalent FSS structures allow the frequency adjustment by the variation of the corresponding strip lengths. The results obtained by the WCIP method and measurements are compared and a good agreement is obtained.