Frequency Selective Rasorber Research Articles

Design of miniaturized and highly selective frequency selective rasorber based on compact spiral resonator

Design of miniaturized and highly selective frequency selective rasorber based on compact spiral resonator

Ionogels, Promising Exploration for Flexible Optically Transparent Tunable All‐Dielectric Electromagnetic Metamaterials

AbstractIonogels, as a novel class of environmentally friendly electronic materials, have received extensive attention. This study successfully prepared P(AM‐co‐AA) ionogel with optical transparency and flexibility via chemical polymerization. Experimental outcomes reveal that the dispersion of anions and cations within the ionogel is effectively controlled by the polymer network, resulting in distinct dispersive dielectric property, which is suitable for applications in electromagnetic metamaterials. Leveraging these properties, two distinct electromagnetic metamaterial devices are developed: An Ionogel‐based Broadband Absorber achieves over 90% absorption across 10.9–25.36 GHz, and An Ionogel‐based Frequency Selective Rasorber (FSR) transmits within 4.62–5.86 GHz, exhibiting minimal insertion loss −1.45 dB and achieves greater than 90% absorption from 13 to 17.8 GHz. High agreement between experimental results and simulations validates the feasibility of utilizing ionogel in electromagnetic metamaterial applications and introduces a novel paradigm and methodology for designing and fabricating flexible electromagnetic metamaterial devices.

Active Frequency-Selective Rasorber With Switchable Dual Operating Modes

Active Frequency-Selective Rasorber With Switchable Dual Operating Modes

Interdigitated resonator based frequency selective rasorber with high selectivity

Abstract This paper investigates a highly selective Frequency Selective Rasorber (FSR) utilizing interdigitated resonators, characterized by a passband exhibiting low insertion loss and the introduction of a second-order passband response in the lossless layer enhances selectivity on both sides of the passband. The lossy unit is implemented by inserting interdigitated resonators on an octagonal ring loaded with lumped resistors, while the lossless layer is constructed with a five-layer structure. Simulation results demonstrate a low Insertion Loss
(IL) value of 0.78 dB at 3.5 GHz. At vertical incidence, the S21>-3 dB bandwidth ranges from
3.41 to 3.67 GHz, and the S11<-10 dB range spans from 2.2 to 8.2 GHz, obtaining two absorption bands on either side of the passband, with absorption rates exceeding 80%. The operating frequency bands are 1.95-3.27 GHz and 3.8-8.4 GHz. The designed FSR exhibits polarization insensitive. To validate simulation results, a prototype FSR was fabricated and tested, with experimental data aligning with simulation results.

High-Selectivity Band-Absorptive Frequency-Selective Rasorber

High-Selectivity Band-Absorptive Frequency-Selective Rasorber

Flexible and transparent ultra-broadband low-profile frequency selective rasorber

An ultra-broadband, low-profile, flexible, and transparent frequency selective rasorber (FSR) is designed based on indium tin oxide (ITO) film. The -1 dB transmission band of the resistive sheet and the bandpass FSS are 0.10 - 8.61 GHz and 3.09 - 7.09 GHz, respectively. By integrating the resistive sheet and the bandpass FSS, a transmission band ranging 1.95 - 6.27 GHz with |S21| larger than -3 dB is achieved, alongside an absorption band ranging 7.34 - 10.83 GHz with absorptance larger than 0.8. Additionally, the FSR presented in this paper is designed by single-layer bandpass FSS and adopts coplanar coupling to realize an ultrabroad transmission band. Its ultra-broadband absorption and transmission performance are verified through experiments and the working principles are analyzed through an equivalent circuit model (ECM). The proposed FSR possesses unique advantages integrating ultrabroad band, optical transparency, flexibility, low profile, and light weight. The proposed FSR exhibits the potential to reduce the out-of-band radar cross-section (RCS), with its optical transparency showing promise for window applications.

Frequency Selective Rasorber with Broadband Absorption and High Selectivity based on Multilayer Graphene-Metal Metamaterials

Frequency Selective Rasorber with Broadband Absorption and High Selectivity based on Multilayer Graphene-Metal Metamaterials

Miniaturized Design of Dual Transmission Frequency Selective Rasorber With Wide Angular Stability

Miniaturized Design of Dual Transmission Frequency Selective Rasorber With Wide Angular Stability

Frequency-Selective Rasorber for Wideband Transmission Based on Hybrid Resistive Sheet With Harmonic Suppression

Frequency-Selective Rasorber for Wideband Transmission Based on Hybrid Resistive Sheet With Harmonic Suppression

A Miniaturized and Highly Stable Frequency-Selective Rasorber Incorporating an Embedded Transmission Window.

In this article, a miniaturized and highly stable frequency-selective rasorber (FSR) incorporating an embedded transmission window is designed. This FSR consists of a lossy layer loaded with resistors, an air layer, and a bandpass layer. The lossy layer is provided with a rectangular, square ring structure loaded with four 180 Ω resistors and four quadrilateral metal plates. The four metal plates are connected to the four corners of the inner ring around the square ring and are radially distributed along the diagonal. The bandpass layer is a square metal patch that a cross-ring slot structure is loaded inside of, and the cross points lie in the direction along the diagonal of the unit. The inner boundary of the cross-ring is composed of two mutually perpendicular and long rectangular elements. This FSR shows an embedded transmission window from 3.63 GHz to 3.80 GHz and has a transmission rate of 93% at 3.72 GHz. Moreover, both sides of the transmission band, namely, 1.86-3.35 GHz and 3.99-8.28 GHz, have an absorption rate of more than 80% and bilateral relative bandwidth of more than 50%. In addition, this structure exhibits excellent miniaturization performance, polarization insensitivity, and angular stability. Finally, a prototype of the designed FSR is processed and measured. The measured results are basically consistent with the simulation results.

An Ultra-Wideband Frequency Selective Rasorber with Low Infrared Emissivity.

The paper proposes an ultra-wideband frequency selective rasorber (FSR) with low infrared emissivity for the composite detection threat of both radars and infrared sensors. Firstly, the equivalent circuit (EC) method based on transmission line (TL) theory is utilized to analyze the absorption/transmission conditions. Then, based on the analysis above, sinusoidal microstrip lines with non-frequency-varying characteristics are adopted in the design, which significantly enhances the transmission bandwidth of FSR. The FSR demonstrates an absorption band ranging from 2.65 GHz to 8.80 GHz and a transmission band ranging from 9.15 GHz to 17.71 GHz. Furthermore, an infrared shielding layer (IRSL) exhibiting low emissivity in the infrared band and high transmittance in the microwave band is applied to the FSR. The simulation and experiment results verify that the IRSL-FSR demonstrates an ultra-wide transmission band ranging from 9.16 GHz to 17.94 GHz and an ultra-wide absorption band ranging from 2.66 GHz to 8.01 GHz. Additionally, it exhibits a low emissivity value (0.23) in 8-14 μm, providing a viable solution to the formidable challenge of radar-infrared bistealth for satellites and other communication-enabled flying platforms.

Optimum design of a novel Ku-band rasorber for RADAR warfare systems using ML neural network

The design, fabrication, and testing of a conformal Frequency Selective Rasorber (FSR) operating at A-T-A mode is designed for RADAR warfare systems. In the design of a miniaturized single-layer FSR element, multiple parameters influencing the absorption and transmission characteristics need to be optimized. This simulation using conventional methods consumes more simulation time. Thus, the geometrical parameters are optimized and predicted using supervised machine learning (ML) techniques to expedite the process. The multiple output regression neural network (MORNN) is used to generate multiple input and output features from the dataset. The ML algorithm is trained using the datasets generated from the electromagnetic solver using which a scalable FSR is synthesized. The reflection coefficient, (|S11|), and transmission coefficient (|S21|) are used as input data, and the dimension of the FSR unit cell for the user input frequency requirements are derived as output data. The extracted dimensions of the FSR offered a small mean square error (MSE) of 0.02 between the desired and observed results. The designed FSR offers absorption at 11.5 GHz and 18.9 GHz while the transmission window extends from 15.02 GHz to 16.09 GHz. The neural network results are endorsed using the EM simulation tool and validated by experimental measurements.

Frequency selective rasorber based on cross bend resonators for wideband transmission and absorption

The wideband absorption and transmission of frequency-selective rasorber (FSR) remain a persistent challenge in the application of radar devices. In this article, a novel high performance wideband FSR design based on cross bend resonators was proposed. The FSR consists of an upper absorption lossy layer, which offers broad absorption and transmission bands, and a lower bandpass frequency-selective surface that enables a highly selective transmission of incident electromagnetic wave. Full wave simulation results showed that this novel design achieves an absorption bandwidth of 83.7% with more than 90% absorptivity in the frequency range of 5.2–12.7 GHz. Furthermore, the passband’s fractional bandwidth for the insertion loss (IL) less than −3 dB is 33.9%, ranging from 14.9 to 21 GHz, with the minimum IL recorded at 0.69 dB at 17.7 GHz. To further verify the proposed method, a prototype FSR with 10 × 10 units of 120 mm × 120 mm was fabricated and the performance of the FSR was tested. The experiment results were in good agreement with the simulated results, and it showed a significant monostatic radar cross-section reduction in the frequency range of 5.3 GHz to 18.3 GHz compared with a metallic plane of the same size.

Active frequency-selective rasorber with wide range passband continuous tunability

In this paper, an active frequency-selective rasorber (AFSR) with a wide tunable range of passband windows is proposed. The proposed AFSR includes an absorption layer, a frequency selective layer, and an air spacer between them. The absorption layer is embedded with resistors to aid in the absorption of out-of-band unprofitable signals, and the frequency selective layer is designed to provide tunable transmission passbands through in-band beneficial signals. A design method for the AFSR embedded with varactors based on equivalent circuit model is proposed. Driven by an applied voltage, the transmission passband of the proposed AFSR can be shifted from 3.4 to 6.9 GHz. The absorption bandwidth covers from 6.4 to 14.1 GHz. In addition, the proposed AFSR exhibits stable performances up to 45° angle of incidence wave. The measurement results of the fabricated prototype are in good agreement with the simulation results. This work provides a feasible solution for flexible simultaneous regulation of radiation and scattering.

Conformal frequency selective rasorber in S, C, X-band with low backward-scattering

In this paper, a polarization-insensitive high transmittance bandpass filter with low radar cross section (RCS) in both S- and X-band is proposed. This is the first study to use the partition layout loading approach for conformal structures with transmissive windows, reducing the operating band RCS. Curved structures have stronger radiation at a smaller angle to the incident wave, and that is how their scattering differs from uniform scattering from flat structures. The structure is divided by analyzing the radiative contribution of different regions. The surface was discussed in regions according to surface angles, and a new partition layout loading method was used to suppress the side currents and decreased backward scattering, achieving a backward RCS reduction of more than 10 dB at 4-8 GHz (66.7%). The bandpass layer operating at 6.9 GHz is designed through equivalent circuit theory. In combination with the lossy layer, absorption above 0.8 at 3.7-5.6 GHz and 9.1-12.5 GHz was achieved. Further, the structure was fashioned into a curved surface with varying curvature, demonstrating its effective absorption and transmission properties across different curvatures. A 15 × 15 cell structure was designed and fabricated, and there was good agreement between the test results and simulation results. The proposed structure has important applications in radomes, conformal structures, and electromagnetic shielding.

Design of Miniaturized Frequency Selective Rasorber Based on Complementary Bandpass FSS for 5G Applications

Design of Miniaturized Frequency Selective Rasorber Based on Complementary Bandpass FSS for 5G Applications

A broadband reconfigurable rasorber radome based on AFSR for RCS reduction

AbstractIn this paper, a broadband reconfigurable active frequency selective rasorber is proposed, which can be used as a radome for antenna radar cross section (RCS) reduction. By tuning the active components, the radome can achieve in‐band RCS reduction and reconfigurable absorptive/transmissive states. In the absorptive state, the max bandwidth with an absorption rate greater than 90% spanning from 1.62 to 5.37 GHz; in the absorptive/transmissive state, 2.2 GHz is the transmissive frequency with the insertion loss of 93% while absorbing in 0.94–2.06 GHz and 2.63–6.5 GHz, which demonstrate impressive characteristics of broadband and a high absorption rate. Additionally, the radome can maintain performance at ±35° angular incidence and is insensitive to incident wave polarization. Furthermore, it features a lightweight and low‐profile design, with a cell electrical size of just 0.078λ × 0.078λ × 0.066λ. The prototype test shows a noteworthy correlation with simulation. This study has wider applications in the electromagnetic stealth of communication antennas and aircraft, as well as in the control of electromagnetic pollution signals in space.

A multifunctional frequency selective rasorber based on hybrid microfluidic-electronic control

In this paper, a multifunctional frequency selective rasorber (FSR) based on hybrid microfluidic-electronic control is presented. The proposed FSR consists of a photosensitive resin-based microfluidic channel and an active frequency selective surface. The lossy layer utilizes the special properties of water (dispersion characteristics, fluidity), and has great advantages in low profile, multifunction, and low costs. Four different responses are realized by the combination of two independent control systems, which provide more degrees of freedom for manipulating electromagnetic waves. In addition, the distribution of electric fields and power loss densities are thoroughly analyzed to derive the physical properties of the proposed structure. Finally, a multifunctional FSR is fabricated and measured, and the simulated and tested results are in good agreement. The proposed structure performs under different polarizations and incident angles (up to 30°), which ensures the stability and security of the communication system in complex environments.

Dual-Polarized Band-Absorptive Frequency-Selective Rasorber With Narrow Transition Band Based on a Multilayer Open Circular Cavity Truncated Cone

Dual-Polarized Band-Absorptive Frequency-Selective Rasorber With Narrow Transition Band Based on a Multilayer Open Circular Cavity Truncated Cone

A Frequency Selective Rasorber with Absorption Bands on Both Sides of Passband Based on Screen Printed Resistive Film

A Frequency Selective Rasorber with Absorption Bands on Both Sides of Passband Based on Screen Printed Resistive Film