Shaowei Bie

Design of a Tunable Low-Frequency and Broadband Radar Absorber Based on Active Frequency Selective Surface

In this letter, we report on the design, fabrication, measurement, and analysis of a tunable low-frequency and broadband radar absorber applied in the frequency range of 1-12 GHz. Numerical simulations indicate that absorbers based on the resistor-loaded frequency selective surface (FSS) can be resistively tuned to give a broadband absorption of exceeding -10 dB between 1 and 12 GHz. Moreover, superior absorbing performance can be achieved by introducing capacitance paralleled with resistance. Measurement results show that the radar absorber, by way of configuration with active FSS (AFSS) controlled by p-i-n diodes, can be tuned to provide a continuously variable reflectivity level of less than -10 dB from 2 to 11.3 GHz with varied bias voltages. Furthermore, experimental results have good agreement with simulations.

Thin and broadband electromagnetic absorber design using resistors and capacitors loaded frequency selective surface

A new method using resistors and capacitors loaded frequency selective surface (FSS) to design thin and broadband electromagnetic absorber is proposed. The effect of the loaded lumped elements on the absorptivity of the absorber is investigated through transmission-line equivalent circuit model. The simulations show that this multiple components loaded FSS (CLFSS) absorber has double changeable abilities of adjusting the real and imaginary parts of its input impedance, which leads to improvement of the absorber’s impedance matching condition and enhancing of the absorber’s absorptivity. Based on the above analysis, two types of CLFSS absorbers were fabricated to confirm the superiority of the multiple components loaded method. One was singly loaded with resistors and the other alternately loaded with resistors and capacitors. Our further measurements show that the alternately loaded FSS absorber has a better absorptivity than only resistors loaded FSS absorber. The alternately loaded FSS absorber with a total thickness of 3.7 mm exhibits a broadband reflectivity response with 98.7% bandwidth over the frequency range from 5.9 to 17.4 GHz below −8 dB.

An ultra-thin broadband active frequency selective surface absorber for ultrahigh-frequency applications

At frequencies below 2 GHz, conventional microwave absorbers are limited in application by their thickness or narrow absorption bandwidth. In this paper, we propose and fabricate an ultra-thin broadband active frequency selective surface (AFSS) absorber with a stretching transformation (ST) pattern for use in the ultrahigh-frequency (UHF) band. This absorber is loaded with resistors and varactors to produce its tunability. To expand the tunable bandwidth, we applied the ST with various coefficients x and y to the unit cell pattern. With ST coefficients of x = y = 1, the tunability and strong absorption are concisely demonstrated, based on a discussion of impedance matching. On analyzing the patterns with various ST coefficients, we found that a small x/y effectively expands the tunable bandwidth. After this analysis, we fabricated an AFSS absorber with ST coefficients of x = 0.7 and y = 1. Its measured reflectivity covered a broad band of 0.7–1.9 GHz below −10 dB at bias voltages of 10–48 V. The total thickness of this absorber, 7.8 mm, was only ∼λ/54 of the lower limit frequency, ∼λ/29 of the center frequency, and ∼λ/20 of the higher limit frequency. Our measurements and simulated results indicate that this AFSS absorber can be thin and achieve a broad bandwidth simultaneously.

Realization of Thin and Broadband Magnetic Radar Absorption Materials With the Help of Resistor FSS

In this letter, a kind of composite radar absorption material consisting of gradient and spiral square resistor frequency selective surface (FSS) and magnetic sheets is designed by HFSS. The use of resistor FSS makes a significant increase of operating bandwidth compared to single magnetic radar absorption materials (mRAMs). Under the condition of normal incident electromagnetic wave, it has remarkable absorptive performance with the reflectivity below -10 dB with a thin thickness of 2 mm in the range of 6-18 GHz. In addition, the composite mRAMs exhibits high angular stability when the incident angle ranges from 0 ° to 30 °. In order to illustrate the importance of resistors, a comparative experiment of structure with nonresistor FSS is made. Experimental results are compared to numerical simulations. They are in agreement with each other.

Optimal Design Of Electromagnetic Absorbers Using Visualization Method For Wideband Potential Applications

Abstract This paper presents a design of broadband electromagnetic absorbers using a square loop shaped frequency selective surface (FSS) loaded with resistors printed on a dielectric substrate. A straightforward visual graphic representation analysis which extends the microwave impedance matching theory into wideband electromagnetic absorbing structure modifying design is carried out on the parametric analysis of the absorbers. Samples of the absorbers with different layers are fabricated. Measured results are in good agreement with the predicted ones, and both show that the novel absorber can reduce reflectivity greatly over a wide frequency range. The study shows that visual graphic representation analysis is simple and practicable to introduce the working principles of the wideband electromagnetic absorbing structure and to derive the best-suited element for wideband absorption.

Design of an adjustable polarization-independent and wideband electromagnetic absorber

An adjustable polarization-independent electromagnetic absorber based on a frequency-selective surface is proposed for both C and X microwave-band applications. The design using a symmetric fan-shaped pattern significantly reduces the sensitivity to different polarizations of normal incident microwaves. To achieve adjustability, PIN diodes are connected between patterned unit cells. By incorporating inductors into the metal patterns, an S-shaped series bias provides the bias voltage to PIN diodes. By tuning the working states of the diodes, an adjustable absorption performance from 4.6 to 13 GHz is achieved for both transverse electric and transverse magnetic polarizations in normal incidence.

A thin and broadband tunable radar absorber using active frequency selective surface

We present a thin and broadband tunable radar absorber using active frequency selective surface (AFSS). The AFSS is composed of a patch type frequency selective surface (FSS) and a PIN diode array. We investigate the impacts of the applied voltage of the PIN diode array and the size of the absorber. Our measurements show that the reflectivity of the absorber can be dynamically adjusted by changing the bias voltages. A good absorption property is observed at the bias voltage of 5 V, with the reflectivity below -10 dB over a frequency band of 5.3-13 GHz, and the thickness is only 5.3 mm.

Broadband Microwave Absorption Properties of Ultrathin Composites Containing Edge-Split Square-Loop FSS Embedded in Magnetic Sheets

A convenient fabrication process about the ultrathin broadband composite microwave absorption material (MAM), which involves a frequency selective surface (FSS) sandwiched between two different magnetic sheets, is presented in this letter. The FSS consists of an array of elements with the geometry of square-loop having a split in each edge (denoted as edge-split square-loop FSS). The top and bottom magnetic sheets were prepared based on silicon rubber filled with sphere-shaped and flake-shaped carbonyl iron powders, respectively. It is revealed by measurement and simulation results that the composite MAM with the FSS that induces multiple resonances has a broad operating bandwidth compared to the traditional magnetic MAM without FSS. The low-frequency resonance can be manipulated by adjusting the size of the split

Low frequency absorption properties of a thin metamaterial absorber with cross-array on the surface of a magnetic substrate

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Broadband microwave absorption property of a thin metamaterial containing patterned magnetic sheet

, while the high-frequency resonance is generally invariable. The composite MAM with the thickness of 2.2 mm has an operating bandwidth with the reflectivity below −10 dB in the frequency range of 4–18 GHz, which is nearly 2.7 times the bandwidth of the traditional magnetic MAM.