Antonio Luiz P. S. Campos

Scattering by FSS on anisotropic substrate for TE and TM excitation

The scattering of electromagnetic waves from frequency-selective surfaces (FSS) composed of rectangular conducting patches mounted on uniaxial dielectric anisotropic substrate is investigated by using a full-wave analysis. The moment method is used in combination with the spectral-domain immittance approach to determine reflection and transmission coefficients of the FSS structure as function of the geometry parameters and dielectric anisotropy. The analysis provides very accurate results compared to those presented by others and to those obtained by measurements.

Analysis of Simple FSS Cascading With Dual Band Response

Numerical and experimental investigations are presented for a dual-band frequency selective surface (FSS) with perfectly conducting rectangular patch elements. In the first step two single-band FSS screens were designed to obtain resonant frequencies at 9.5 GHz and 10.5 GHz, each one with about 1.5 GHz bandwidth at -3 dB. In the second step these single FSS screens were cascaded and separated by an air gap layer to achieve a dual-band response. The Moment Method is used to analyze the structures single band. After this, a numerical cascading technique is used to analyze the effect of the air gap between the cascading structures. Numerical and measured results were compared and a good agreement was obtained.

Wide stop-band cascaded frequency selective surfaces with Koch fractal elements

Numerical and experimental investigations are presented for a cascaded frequency selective surface (FSS) with Koch fractal conducting patch elements. The work is developed in two steps. In the first step two Koch fractal FSS screens are designed using the Ansoft Designer™ software. In the second step these FSS are cascaded and separated by an air gap layer to improve the bandwidth behavior. The structures are cascaded using Teflon spacers and screws to obtain the air gap. Thereafter, a numerical cascading technique is used to analyze the effect of the air gap between the cascading structures.

A design proposal for ultrawide band frequency selective surface

In this paper a three layer FSS is described which provides a ultrawide band (UWB) response. The layers use plain rectangular patches, and rectangular patches with one or two notches which provide multi-band responses; by cascading them an UWB response is obtained covering the band 4.05 - 14.12 GHz, for vertical polarization and the band 5.05 - 15.00 GHz, for horizontal polarization. Transmission properties of the proposed structure were simulated and measured.

Performance optimization of microstrip antenna array using frequency selective surfaces

This paper presents the application of frequency selective surfaces in antenna arrays as an alternative to improve radiation parameters of the array. A microstrip antenna array between two FSS was proposed for application in WLAN and LTE 4G systems. Several parameters have been significantly improved, in particular the bandwidth, gain and radiation efficiency, compared with a conventional array. Numerical and measured results are presented.

Scattering Parameters of FSS on Anisotropic Layers at Millimeter Wave Frequencies

The analysis of periodic structures on anisotropic substrates is presented for incident millimeter waves. Frequency selective surface structures composed by a periodic array of conducting crossed dipoles on anisotropic layers are analyzed. A full-wave analysis for the problem of scattering is performed. The formulation uses the moment method in combination with the immitance approach, in the Fourier domain, to determine the scattering parameters of the considered structures. A set of entire-domain type basis functions is used in the expansion for the unknown induced current. This analysis is computationally efficient, and its accuracy is verified by the agreement between results obtained in this work and those available in the literature, for particular cases.

A new compact koch fractal patch antenna on an EBG ground plane

A new antenna with Koch fractal patch elements of the first level (KR1) and electromagnetic bandgap in the ground plane (EBG-GP) is proposed in this paper. The design is based on Ansoft HFSSTM software and in order to validate the model several prototypes are built and measured. A better impedance matching for the device is obtained using the inset-fed technique. The measured return loss values for the proposed antennas at the resonant frequencies are lower than -20 dB. The KR1 EBG-GP antennas show corresponding resonant frequencies values lower than the rectangular patch antennas with inset-fed. That results in a size reduction factor around 28% for these structures resonating at 2.45 GHz.

Spectral domain analysis of double screen frequency selective surfaces

This paper presents a numerical investigation for a double screen frequency selective surface (FSS) with perfectly conducting rectangular patch elements. The analysis uses a full wave technique to obtain the scattering characteristics. The analysis combines the immitance approach and the method of moments to obtain the scattered fields and, consequently, the scattering characteristics of the structure. For validation of the analysis, numerical results are compared with measured and numerical results presented by another authors. A good agreement was obtained with experimental results.

A comparison between the equivalent circuit model and moment method to analyze FSS

A comparison between the equivalent circuit model and moment method was done. Numerical results were obtained with the equivalent circuit model using Matlab routines and with moment method using the Ansoft Design¿ software. Experimental results obtained from literature were compared with numerical results. A good agreement was observed. Two dual band geometries were considered: the Jerusalem cross and the double square loop. The parameters used to comparison were analytical complexity, accurate, and computational effort. For this last parameter and considering the worst case, the equivalent circuit method was run in 55 ms, while the method of moments took around 4 hours.

Improving stop-band properties of frequency selective surfaces with Koch fractal elements

Design and experimental investigations are presented for a cascaded frequency selective surface (FSS) with perfectly conducting Koch fractal patch elements. The work was developed in two steps. In the first step two Koch fractal FSS screens were designed using the software Ansoft Design¿ and several prototypes were built. In the second step these FSS screens were cascaded and separated by an air gap layer to improve the bandwidth behaviour. The structures are cascaded using Teflon spacers and screws to obtain the air gap. The FSSs were built on a RT-Duroid 3010 substrate. Good agreement was observed between simulated and measured results.