Study on Analysis and Simulation of Novel Frequency Selective Surfaces

In this paper, a frequency selective surface (FSS) element has been presented based on substrate integrated waveguide (SIW) technology for improved EM performance. The SIW cavity results in the generation of additional resonance, which combines with the resonance of FSS shows a relatively wider bandwidth (BW). Furthermore, the FSS based on SIW exhibits a sharp roll-off performance with flat transmission characteristics. The FSS element is designed to operate in Ku-band near 15.0 GHz for satellite application. Two design examples have been reported for the dual band and broadband response. The estimated results have proven the superiority of the SIW cavity FSS over its conventional form.

This paper proposes a technique that uses the small-metal width of a frequency-selective surface (FSS) element to suppress the change in beamwidth due to the undesired reflection from other FSSs. FSSs reflect low-level electromagnetic waves that are expected to pass through essentially the FSSs outside of the desired reflection bands, and generate these low level reflections from other FSSs as undesired reflections. Electromagnetic field analysis based on a dual-band antenna structure shows the relationship between the metal width and the reflection coefficient of the FSS element, and the relationship between the metal width and the beamwidth in the desired band and the other band. This paper clarifies that the small-metal width of the FSS element can be used to reduce the change in beamwidth outside the desired band.

This paper presents a design of dualband frequency selective surface (FSS) element design based on SIW cavity (SIWC) technology and its performance analysis. The proposed dualband FSS is modelled using a combination of two FSS elements. A cross-slot element has been enclosed by a square slot to design the proposed shape. The structure shows dualband response at two different frequency bands C- and Ku-bands with sharp roll-off performance characteristics. The performance of the structure has been estimated using commercial CST Microwave studio. The simulation results show the higher selectively, very good isolation between the bands and stable performance characteristics compared with its equivalent conventional planar version.

This paper proposes a fractal square loop frequency selective surface (FSS) with dual-band stop behavior. The FSS elements are etched on FR-4 substrate to attenuate signals at GSM900, GSM1800 and IMT2000 frequency bands while transmitting other microwave signals. The unit cell geometry is a modification of the conventional square loop which shows an improvement in stability for oblique incidence up to 45° for both TE and TM polarizations. The proposed FSS shifts the onset of a grating lobe to the outside of the frequency of interest without compromising the target resonant frequencies. The measured results are shown to be in a very good agreement with the simulated results.

In this article, a via‐based 2.5‐dimensional (2.5D) frequency selective surface (FSS) is proposed to realize a quasi‐elliptical bandpass response with high frequency selectivity. Each FSS element is composed of two parts. Part A is a double‐layer metallic circular patches, which are etched on both sides of a thick substrate and connected by a central big metallic via and several small vias. Part B is a single layer metallic circular patch etched on a thin substrate. The proposed FSS features several transmission/reflection zeros, exhibiting a flat transmission in the passband and fast roll‐off out of band. By investigating the electric field distributions, two paths of electromagnetic wave (EMW) propagation are observed, and the physical mechanism of the transmission/reflection zeros of the FSS is obtained. A prototype of the FSS is fabricated to verify the design, and the measured transmission responses agree with the simulated ones.

This paper presents a novel polarization-insensitive dual-band frequency-selective surface (FSS)-based electromagnetic shield. The miniaturized FSS unit cell consists of a modified Jerusalem crossed loop and a corner-modified square loop. These FSS elements are arranged in a co-planner configuration over a single-layer Rogers 5880 substrate and simultaneously offer effective shielding in the X- and Ku-bands. Moreover, the FSS manifests polarization-independent and angularly stable band-reject filter characteristics over various oblique angles of incidence for both the TE and TM polarizations with virtuous attenuation at both resonances. In addition, the FSS structure is modelled into an equivalent lumped circuit to better analyze the phenomenon of EM wave suppression. A finite prototype of FSS is fabricated and tested. The simulated and measured results are in good agreement, thus making it a potential candidate for RF shielding/isolation applications.

An entire domain current expansion set is found for the tripole frequency-selective surface (FSS) using the singularity expansion method (SEM). The SEM analysis is performed on a thin wire model of an isolated FSS element. The SEM natural current modes yield a highly efficient entire domain expansion set for use in a Floquet moment-method analysis of the FSS array. The SEM analysis yields an optimum set of expansions functions without any prior knowledge about the FSS element. >

Sandwich structures with frequency selective surfaces have been widely used to fabricate low-observable radomes. Traditional frequency selective surfaces were made of metals, such as copper and aluminum. There were problems when used the frequency selective surfaces with the sandwich structures, such as a bonding layer and thermal mismatch. Because of the thermal mismatch between the sandwich structures and the metals, mechanical properties of the sandwich structures usually decreased. To avoid these disadvantages, a new type of composite frequency selective surface was put forward in this study. A four-legged slot-array frequency selective surface and a square-aperture array frequency selective surface were fabricated by cutting carbon fiber/epoxy composites. Free-space method and finite-element method were carried out to evaluate the electromagnetic transmission characteristics of the frequency selective surface specimens, respectively. Results show that the composite frequency selective surface with four-legged slot array can realize the function of frequency selection, and its minimum transmission loss can be decreased by increasing the electrical conductivities of the composite material, adjusting the thickness, and increasing the aperture-to-cell ratio of it. For the composite frequency selective surface with square-aperture array, grating lobes come closely after its resonant frequency, although its minimum transmission loss is very close to zero.

This work presents an analysis of frequency selective surfaces (FSSs) with Dürer's pentagon pre-fractals patch elements. The proposed FSSs are composed by a 2-D periodic array of metal pre-fractals elements printed on a dielectric substrate. A parametric analysis is performed using Ansoft Designer commercial software in terms of the FSS periodicity and of the fractal iteration number used in the FSS elements. The structures are proposed to behave like stop-band spatial filters and exhibit interesting features to be used in the design of compact FSSs with broadband or dual band responses.

In this paper, a high gain ultra wideband (UWB) antenna by employing a single layer frequency selective surface (FSS) as a reflector is presented. The impedance bandwidth of the proposed antenna is 155% (1.9 to 15.2 GHz) with peak gain 5.9 dBi. Further the gain of the proposed UWB antenna has been improved by placing a frequency selective surface (FSS) array reflector underneath the UWB antenna. The unit element of FSS is a circular loop structure and further modified in to 5X5 element array. The UWB antenna with FSS reflector showed the enhancement in gain from 5.9 dBi average peak gain to 9.2 dBi and it's almost stable in the higher band. The comparative analysis of gain and radiation patterns of antenna with and without FSS has been discussed to observe the effect of FSS on the antenna performance. The full wave EM simulation has been carried out by using CST MWS.

In this study, the frequency selective surface (FSS), absorbance and sensing applications of new unit cells comprised of single, double and quad U‐shaped metallic elements are numerically and experimentally investigated. The numerical results are realised by using finite integration technique‐based electromagnetic simulation software, CST Microwave Studio. Experimental results are obtained by means of Agilent N5234A PNA‐L vector network analyser. The simulated and measured results of U‐shaped FSSs are carried out by using two different ways; periodic unit cell and waveguide boundary conditions. The single and quad U‐shaped FSS elements show a single band‐stop filter property, whereas the double U‐shaped FSS shows a dual‐frequency band‐stop filter behaviour. Absorber and sensor applications of the proposed U‐shaped FSSs are illustrated both numerically and experimentally. The three types of U‐shaped FSS structures show a narrowband absorbance which has potential in biomedical and sensing applications. Single and dual absorber characteristics are observed with a 90% absorbance. For the sensor configuration, 800 MHz bandwidth is obtained for sensing different materials showing that it is possible to realise different microwave sensor studies in industries of food and agriculture. Simulated and measured results are compared for FSS, absorber and sensor configurations, and the results show a good agreement with each other.

A single-layer substrate frequency selective surface (FSS) made of miniaturized elements is proposed, with two controllable passbands obtained. Each FSS element consists of a loop wire on the top metal layer and its complementary pattern etched at the bottom one, which provides two transmission poles separated by a transmission zero. An equivalent circuit model is given for predicting the characteristics of the designed FSS, and a good agreement between the simulated and measured transmission coefficients is obtained. Furthermore, the cases of oblique wave incidence and cascading FSSs are also measured and examined.

Frequency selective surfaces (FSS) are proposed for the design of a broadband resonator antenna. Conducting element FSS presents negative reflection phase, this property of the surface allows obtaining subwavelength cavities. Once such a cavity is inserted in the traditional half wavelength resonator, bandwidth of the last one can be improved. (4 pages)

Results of modeling, design, simulation and fabrication are presented for a high-gain cavity resonance antenna (CRA), employing highly-reflective patch-type superstrates. In order to determine the resonant conditions, the antenna is first analyzed using the transverse equivalent network (TEN) model, as well as the well known simple ray-tracing method. Prior to that, a highly-reflective patch-type frequency selective surface (FSS) is designed in order to be employed as the superstrate layer of the CRA. Next, a 2.5-D full-wave analysis software package, based on the method of moments (ANSOFT Designer v4.0), is utilized to analyze the antenna structure. Using this full-wave analyzer, the input impedance properties of an actual antenna are investigated as well. Then, a 3-D full-wave analyzer, based on the finite element method (ANSOFT HFSS), is used to extract the directivity and radiation patterns of the CRA, taking into account the finiteness of the substrate, superstrate and ground plane. Some previously unaddressed issues, such as the effects of the FSS superstrate on the input impedance characteristics of the probe-fed microstrip patch antenna, acting as the excitation source of the CRA are also studied. The effects of the highly-reflective FSS superstrate size on the CRA directivity, and explicitly its aperture efficiency, are investigated as well. A comparative study is also performed between CRAs with patch-type FSS and high permittivity dielectric superstrates. Measurement results are provided to support the modelings and simulations.

Absorbing properties of frequency selective surface absorbers with cross-shaped resistive patches