Dual-band Frequency Selective Surface Research Articles

Low-Profile, Highly-Selective, Dual-Band Frequency Selective Surfaces With Closely Spaced Bands of Operation

We present a new design of a dual-band frequency selective surface (FSS) with closely spaced bands of operation and a highly-selective frequency response at each band. A multi-stage design procedure is also proposed for the design and synthesis of this class of frequency selective surfaces. The design procedure is based on synthesizing the desired device from its equivalent circuit parameter values. An approximate analytical technique is provided, which can be used to determine the values of the equivalent circuit parameters of this dual-band device from the basic system level characteristics of its transfer function including the center frequencies of operations of its two bands of operation and the bandwidth at each of these bands. The use of this design procedure is described in detail by a design example which follows the proposed design procedure step by step; the validity of the procedure is verified using full-wave EM simulations and experimental characterization of a fabricated prototype of the proposed device. Experimental characterizations of this device show that it has a stable frequency response as a function of angle of incidence for both the transverse electric (TE) and the transverse magnetic (TM) polarizations. This stability is attributed to the extremely small overall thickness of the structure as well as its small unit cell dimensions.

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.

Double Screen FSSs with Multi-Resonant Elements for Multiband, Broadband Applications

Design investigations are presented for double screen frequency selective surfaces (DSFSSs) with multi-resonant elements. The DSFSS is composed of two identical single layer frequency selective surfaces (FSSs) separated by a foam layer. By tuning the thickness of the foam, a four-band FSS with improved S-band performance and a dual-band band-stop FSS with broad bandwidths and rapid rolloffs are designed. Both designs are angle and polarization insensitive. The Fabry-Perot interferometer (FPI) theory demonstrates that DSFSSs with a large distance between the metallic arrays are not suitable for broadband band-stop applications due to the interruptions of undesired transmission peaks, which are the results of array interference. An equivalent circuit model is developed to give an insight into the response of the DSFSS. Experimental verifications are carried out. The calculated results agree well with the measured ones.

A Miniaturized Dual-Band Frequency Selective Surface (FSS) With Closed Loop and Its Complementary Pattern

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.

Dual-Band Capacitive Loaded Frequency Selective Surfaces With Close Band Spacing

In this letter, a novel miniaturized dual-band capacitive loaded frequency selective surface (FSS) is presented, in which each periodic cell consist of two neighboring capacitive loaded ring slot resonator with the same dimension. To eliminate the undesired coupling between unit cells, the unit cell is placed in a Faraday cage structure created by arrays of metallic substrate vias. An S-band dual-band FSS with such structures is designed and fabricated, both simulated and measured results show that the proposed FSS provides high transmission with close band spacing at 2.5 and 3.5 GHz, and there is no other resonance frequency up to 15 GHz. Furthermore, the FSS dimension is miniaturized to 0.082 lambda (lambda refer to the resonant wavelength of 2.5 GHz). Also, it is not sensitive to the angle of oblique incidence wave. The design and discussion about dual-band FSS loading with lumped elements is presented for the first time.

A Second-Order Dual X-/Ka-Band Frequency Selective Surface

In this letter, a new technique for designing dual-band frequency selective surfaces with arbitrary bands of operation, with second-order band-pass responses at each band of operation, is presented and experimentally verified. The technique is based on utilizing a particular topology of a second-order band-pass microwave filter and synthesizing its constituting elements using periodic structures with inductive, capacitive, or resonant type surface impedances. The result is a low-profile planar structure composed of three metal and two dielectric layers that acts as a spatial version of the dual-band microwave filter.

Dualband frequency-selective surfaces using substrate-integrated waveguide technology

This paper proposes a dualband frequency-selective surface (FSS) based on substrate-integrated waveguide (SIW) technology. This novel dualband FSS is constructed using double square loop slots (DSLSs) and an SIW cavity. Its frequency performance is investigated by numerical simulation using the finite difference frequency domain (FDFD) method. Another dualband FSS, constructed using convoluted double square loop slots (CDSLSs) and an SIW cavity is also investigated in order to get close passband spacing. Simulation results show that these dualband FSSs have the advantages of higher selectivity and passband insensitivity to the incident angles and polarisations, compared with conventional multiband FSSs. Experiments are carried out to verify the simulated results, and the measured results show a promising performance of the proposed FSS.

Automatic design of inductive FSSs using the genetic algorithm and the MoM/BI-RME analysis

This paper describes an automatic procedure for the design of frequency selective surfaces (FSSs), consisting of thick metal screens periodically perforated with apertures. The optimization tool is based on the genetic algorithm and embeds a recently developed analysis method, named the MoM/BI-RME method. The optimization code selects the most suitable shape and dimensions of the aperture elements in order to satisfy the design specifications. An example reports the synthesis of a dual-band dual-polarization FSS.

Fractal FSS: a novel dual-band frequency selective surface

The multiband properties of self-similar fractals can be advantageously exploited to design multiband frequency selective surfaces (FSS). A Sierpinski dipole FSS has been analyzed and measured and the results show an interesting dual-band behavior. Furthermore a near-field measurement technique is applied to characterize the FSS response to different angles of incidence. Finally, it is shown that it is possible to tune the FSS response by properly perturbating the geometry of the Sierpinski dipole.

Dual band FSS with fractal elements

Experimental and computed results of a frequency selective surface (FSS) based on a certain type of fractal element are presented. The fractal element is a two iteration Sierpinski gasket dipole. Owing to the dual band behaviour of the two iteration Sierpinski gasket dipole, two stopbands are exhibited within the operating frequency band. This behaviour is obtained by arraying one simple element in a single layer frequency selective surface (FSS).

The effect of perturbating a frequency-selective surface and its relation to the design of a dual-band surface

A single-layer dual-band frequency selective surface (FSS) created by the perturbation of a single-band dipole array is studied. A simple algebraic formulation is derived to analyze both element and spacing perturbations. Guidelines are then proposed to allow dual-band FSSs to be designed with no anomalous behavior occurring in the two desired bandstop responses. Examples of unsuccessful and successful dual-band FSSs are calculated.