Bandpass Frequency Selective Surface Research Articles

Transmission-Type Frequency Selective Surface with Polarization Modulation

Abstract In this work, a transmission-type frequency selective surface (FSS) with polarization modulation is proposed. This design achieves cross-polarized transmission under both x- and y-polarized normal incidences, while supporting co-polarized transmission at a 45° incidence polarization angle. Consequently, the structure can serve as a polarization rotating FSS (PR-FSS) or a conventional bandpass FSS. The design consists of two fundamental units, corresponding to x- and y-polarized PR-FSS, arranged according to a specific group array paradigm. This arrangement preserves the cross-polarization transmission functionality of each unit. In addition, at a 45° polarization angle, the symmetry of the paradigm with respect to the electric field enables it to support co-polarized transmission. A prototype containing a 12 × 12 element array is constructed and tested. The measured results demonstrate good agreement with the simulation results.

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.

A broadband second-order bandpass frequency selective surface for microwave and millimeter wave application.

This paper presents a frequency selective surface (FSS) with a wideband second-order bandpass response in the dual-band of microwave and millimeter wave. The overall structure consists of three layers of metal pattern and two layers of thin dielectric substrate. The top and bottom metal layers have capacitive patches with integrated curled Jerusalem cross slot resonators, while the intermediate metal layer has an inductive grid structure with cross-shaped slot resonators. The incorporated slot resonators play a pivotal role in achieving the desired transmission poles or zeros, which enable a wideband second-order filtering response in the dual-band and a quick roll-off at the passband edges, increasing the efficacy of electromagnetic shielding. To fully investigate the structure's frequency response, an equivalent circuit model of the structure is created, spanning the complete frequency range of 5-50 GHz. Physical samples are created and measured to confirm the suggested approach's efficacy. The passband center frequencies of the FSS are found at f1 = 19.42 GHz and f2 = 42.78 GHz, and the - 3dB bandwidth is 4.34 GHz (17.25-21.59 GHz) and 8.54 GHz (38.51-47.05 GHz), respectively. The simulation results align well with the experimental data. The transmission response rapidly transitions from the passband to the stopband at the passband boundaries.

Bandpass frequency selective surfaces with fast roll-off characteristics

We propose a bandpass frequency selective surface (FSS) with fast cut-off characteristics and low insertion loss. It consists of a compact high-frequency hybrid compression board with five metal layers, two Rogers RO4003C layers, and two F4B layers. The hierarchical fitting of equivalent circuits is utilized to analyze the FSS, which maintains angular stability for dual-polarized electromagnetic waves at incidence angles of less than 20 degrees. Under normal incidence, transmission amplitudes in the K-band exceed −0.87 dB. Furthermore, the proposed FSS achieves a roll-off rate of 87.6 dB GHz−1, which can be applied in dual-frequency observing systems for millimeter astronomy.

A miniaturized dual band pass frequency selective surface insensitive to oblique angles and polarizations of wave

Abstract A Dualband Pass Frequency Selective Structure (DPSFSS) with miniaturized elements is proposed in this article. The miniaturized elements induce high inductance and capacitance values. The meandered line concept is used which extensively increases inductance of the dipole element. Very large capacitance is obtained between two meandered elements which have wide common area perpendicular to electric field for wave propagating in Z-direction. Two pass band poles and two zeros are obtained by perpendicular arrangement of meandered patterns on two sides of the substrate. Orthogonal arrangement of patterns ensure polarization symmetry (polarization insensitive) for Transverse Electric (TE) and Transverse Magnetic (TM) modes of exciting wave. Two pass band pole frequencies are positioned at 1.84 GHz and 4.53 GHz with low Insertion Losses (IL) of 0.67 dB and 1 dB, respectively. The lower and higher frequency bands have factional bandwidths of 41 % and 46 %, respectively. The transmission nulls occupy 2.8 GHz and 6.58 GHz frequencies. The structure is miniaturized to 0.032λ 0 × 0.032λ 0 dimensions with respect to lowest resonance residing at 1.83 GHz. The low IL at both pass bands is realized despite of using a lossy FR-4 material that can be improved to less than 0.5 dB at both the bands using less lossy materials such as F4BME or RO4003C. The proposed DPSFSS design is elaborated using Equivalent Circuit Model (ECM) and Surface Current Distribution (SCD). Measurements are performed on fabricated DPSFSS prototype and it is observed that the measured results coincide well with the simulated response. Angle stability of the DPSFSS is excellent and no unwanted resonances are observed at oblique angles upto 80° for dual polarizations of wave.

Design and analysis of a complementary structure-based high selectivity tri-band frequency selective surface

This work presents a novel tri-band bandpass frequency selective surface (FSS) that achieves high-order filtering responses in different frequency bands by means of a complementary structure. The proposed FSS is composed of three metal periodic arrays, which are separated by multilayer dielectric substrates. The gridded-double convoluted loop (G-DCL) structure, which is the middle layer structure, is a hybrid resonator that generates different resonant frequencies. The top and bottom layer structures are designed as complementary structures to the middle layer. To accurately describe the frequency responses, an equivalent circuit model (ECM) has been constructed over the entire band from 0 to 16 GHz. The results of the simulation indicate that the developed FSS can generate three pass-bands operating at 3.79 GHz, 8.34 GHz, and 12.52 GHz, respectively, and − 3 dB fractional bandwidths are 52.8%, 13.7%, and 19.7%. The transmission responses at the edges of each passband show a quick roll-off from the passband to the stopband, and there is significant out-of-band suppression between adjacent passbands. Moreover, the FSS maintains excellent angular and polarization stability within a 50° range. For verification, the tri-band FSS has been fabricated and tested. The experimental results match the simulation results, validating the accuracy of the FSS design.

Wideband low-RCS and gain-enhanced antenna using frequency selective absorber based on patterned graphene

In this paper, a double-layer patterned graphene-based frequency-selective absorber (DGFSA) is proposed as a means of reducing an antenna’s radar cross-section (RCS) while simultaneously increasing its gain. The antenna consists of a patch antenna with Multi-Graphene Frequency Selective Absorber (MGFSA) mounted on top. The DGFSA consists of double-layer patterned graphene and a band-pass frequency selective surface (FSS). Two patterned graphene lossy layers with different square resistances are used, which broaden the electromagnetic (EM) wave absorption bandwidth of the DGFSA, thus greatly reducing the out-band monostatic RCSs of the patch antenna. Meanwhile, due to the quasi-Fabry-Perot (F-P) effect, the gain of the proposed antenna is enhanced by 2.4 dB. Additionally, the low-RCS antenna reduces the monostatic RCS from 1.32 to 17 GHz under y-polarization and from 1.4 to 16.8 GHz under x-polarization, respectively. Furthermore, a decrease in the bistatic RCS is accomplished. Results from simulations and measurements match up nicely, which means the antenna we proposed has a good application on the stealth platform.

Novel Polyimide-Based Conformal Bandpass FSS for X-band RADAR Communications

A linearly polarized wide bandpass frequency selective surface (FSS) for RADAR communication application has been presented. The proposed FSS is constructed in a single layer with a size of 0.25 λ0. This FSS utilizes a rhombus slot comprised of a head slot and a meander line to provide a single-wideband resonance. The proposed FSS operates in the X-band communication frequency range from 7.98 to 12.1 GHz (4.12 GHz) and achieves a minimum insertion loss of 0.1 dB, respectively. The designed FSS is developed on a flexible substrate with a low profile of 0.05 mm. The FSS exhibits stable angular performance in the scope of incidence angle of 60º for both TE and TM modes. An equivalent circuit model is designed to depict the desired frequency response. Furthermore, a bending analysis has been carried out to verify the conformal nature of the proposed unit cell. The prototype is fabricated and the performances are validated with experimental results.

Dual-Notched UWB Orthogonal MIMO Antenna with Improved Gain Characteristics Using Frequency Selective Surfaces for Wireless Communication Applications

In this paper, a complementary split ring resonator (CSRR) loaded compact CPW-fed circular shaped monopole UWB antenna with dual band notch characteristics is designed on an FR-4 substrate. The propounded band-notched UWB antenna is integrated with two frequency selective surface layers referred as bandpass frequency selective surface (FSS-1) and reflector (FSS-2) to offer enhanced radiation performance. Bandpass FSS-1 enhances the gain of the antenna by improving directivity and reflector FSS-2 reflects back the backside radiation of the proposed antenna towards the forward direction thereby increasing gain and directivity of the proposed antenna. Furthermore, a two-element orthogonal MIMO antenna is proposed with improved gain using two FSS layers. The complete configuration of the proposed two-element MIMO antenna consists of CSRR-based radiating patches, monopole ground planes and two integrated FSS layers. The proposed MIMO antenna operates in UWB range from 3.46[Formula: see text]GHz to 16.02[Formula: see text]GHz with dual notches at 3.9[Formula: see text]GHz and 7.2[Formula: see text]GHz. Isolation between MIMO elements is greater than 23 dB. Both antennas are fabricated and investigated at 5.9[Formula: see text]GHz for vehicular communications. Maximum gain improvements of 8 dB and 6.4 dB are observed in case of the presented single element and MIMO antenna within the entire operating band due to the integration of dual FSS layers. The diversity performance of the suggested MIMO antenna is investigated by analyzing mean effective gain, envelope correlation coefficient, channel capacity loss and diversity gain parameters. The proposed MIMO antenna is a suitable candidate for vehicular and UWB wireless communication applications.

A Conformal Miniaturized Bandpass Frequency-Selective Surface With Stable Frequency Response for Radome Applications

A Conformal Miniaturized Bandpass Frequency-Selective Surface With Stable Frequency Response for Radome Applications

A novel fast roll-off bandpass frequency selective surface for stealth applications

A novel frequency selective surface (FSS)-based spatial bandpass filter for TM-polarized waves is reported. The unit cell of the proposed FSS consists of a dielectric substrate with two conducting layers on opposite sides. One magnetic resonator is placed on the top conducting layer, while two pairs of electric resonators are positioned on the bottom conducting layer to provide a fast roll-off bandpass characteristic. The simulated values of the −3 dB to −10 dB roll-off factor (RF) for the proposed structure are 140 and 280 dB/GHz on the lower and upper sides of its passband, respectively. To validate the simulation results of the proposed structure, a prototype of the FSS-based filter was fabricated and tested experimentally. Furthermore, the present simulation results are benchmarked with the band-pass FSSs reported in the literature, demonstrating an advantage of the proposed filter over the filters mentioned in previous works.

22/43 GHz low-insertion-loss dual-polarized multi-layer bandpass frequency selective surfaces for millimeter astronomy

We design a frequency selective surface (FSS) capable of transmitting K-band and reflecting Q-band radio waves. The equivalent circuit approach assists the distribution of multi-layer FSS to achieve a third-order bandpass response with an incident angle of less than 30°. The unit structure consists of three metal layers embedded with two dielectric substrates. Especially, the FSS provides a 3 dB transmission bandwidth range from 18.6 to 26.7 GHz with a maximum measured insertion loss of 0.61 dB. Hence the proposed polarization-insensitive FSS with low insertion loss can be applied in the observation system of millimeter astronomy.

A Bandpass Frequency-Selective Surface Based on an Aramid-Paper Honeycomb Sandwich Structure

A Bandpass Frequency-Selective Surface Based on an Aramid-Paper Honeycomb Sandwich Structure

A Low RCS Waveguide Slot Antenna array with Metamaterial Absorber

We propose a novel design to reduce the radar cross section (RCS) of ridged waveguide slot antenna array with metamaterial absorber (MMA). The MMA consists of metallic pattern and solid metal on sides of a dielectric slab, of which the absorbing characteristics and mechanism are analyzed. The PEC ground plane of a ridged waveguide slot antenna array is covered by MMA. Both the simulated and measured results show that compared with the waveguide slot antenna array with a PEC ground plane, the RCS of proposed antenna array are reduced dramatically without degradation of antenna performance. Combining with the bandpass frequency selective surfaces technology, the guideline illustrated by the proposed examples will serve as a good candidate for the future design of low RCS antenna.

Design of Wideband Two-Sided Bandpass Frequency Selective Surface for X, Ka, and Ku Band Application

A novel wideband bandpass frequency-selective surface functioning at X, Ku, and Ka bands is proposed in this article. The designed FSS has a metallic square loop and a circular ring, and they are printed on both sides of the FR4 substrate. The proposed design FR4-based single-layer FSS is operating from 11.075 GHz to 22.075 GHz with a fractional bandwidth of 66.36%. The parameters of the square loop and circular ring regulate the characteristics of the passband. The optimum dimension of these parameters is obtained with parametric analysis. The proposed structure is measured and fabricated. However, the measured results strongly agree with the simulated results, which authenticate the proposed design performance.

A configuration to double the gain of pyramidal horn antenna using single layer frequency selective surface

AbstractA gain enhancement technique in pyramidal horn antenna using a slot type band pass frequency selective surface (FSS) is presented. The horn antenna without FSS has achieved a measured gain of 10.5 dBi at 10 GHz, while the antenna with the single layer slotted FSS yields an enhanced measured gain of 14.2 dBi (an improvement of 3.7 dB or 134%). Conventionally, such a gain enhancement would 5 times increase in its dimensions (flaring). However, the authors achieve the same with only 2 times increase in dimensions. Another interesting value addition of the proposed idea is that an FSS sheet can be added to the existing horn antenna to increase its gain without altering the antenna itself. Such a scheme is highly beneficial in strategic applications. The proposed gain enhanced horn antenna can be recommended to be utilised in several X‐band applications, such as radar systems (weather, surveillance, traffic control and military), satellite communications and point–point microwave links that require high gain and small form factor.

FSS-inspired transmitarray for dynamic beamforming and gain control.

In this paper, we propose a concept of combining the methodology of phase coding modulation with frequency selective surface (FSS) inspired transmitarray (TA) to achieve the ability of dynamical beamforming and gain control in microwave regime. The TA element composed of five-layer stacked bandpass FSS units separated by small air gaps. Each FSS unit comprises a metallic octagon slot with a pair of varactor diodes loaded along the polarization direction. The elaborately designed feeding network makes it possible to modulate the transmission phase of each element. Different phase coding sequences are performed through changing the bias voltage configurations, then the radiation far field of the proposed TA can be tailored in real time. Dynamic beamforming and gain control under different encoding arrangements are exhibited to demonstrate the physical mechanism of electromagnetic (EM) manipulation with this method. The proposed strategy is verified by numerical simulations and experiment. This work adds new function for TA and can reshape its application prospect, such as reconfigurable beam emitter for multilink data transmission, long range point-to-point (PTP) wireless links and radio frequency energy harvesting.

X-band frequency selective surface with low loss and angular stability

A bandpass frequency selective surface (FSS) with low loss and angular stability based on three metal layers is proposed in this paper. The top and bottom resonant layers are coupled through a metal ring layer to build the FSS structure. The equivalent circuit model is derived to explain the operation principle of the proposed FSS. In the design, two transmission zeros (TZs) are generated at both sides of the passband contributing to the high selectivity performance. Furthermore, current distributions are given to analyze the generation mechanism of the TZs. The performance of the proposed FSS is insensitive to the polarization and angle of the incident wave. To verify the performance, a prototype of the FSS is fabricated, whose measured results agree with the simulated ones. The FSS shows low-profile of about 0.07λ (λ is the free space wavelength at the center frequency).

Wideband low-scattering metasurface with an in-band reconfigurable transparent window

Active metasurfaces with dynamically reconfigurable functionalities are highly demanded in various practical applications. Here, we propose a wideband low-scattering metasurface that can realize an in-band reconfigurable transparent window by altering the operation states of the PIN diodes loaded on the structures. The metasurface is composed of a band-pass frequency selective surface (FSS) sandwiched between two polarization conversion metasurfaces (PCMs). PIN diodes are integrated into the FSS to switch the transparent window, while a checkerboard configuration is applied in PCMs for the diffusive-reflective function. A sample with 20×20 elements is designed, fabricated, and experimentally verified. Both simulated and measured results show that the in-band functions can be dynamically switched between beam-splitting scattering and high transmission by controlling the biasing states of the diodes, while low backscattering can be attained outside the passband. Furthermore, the resonant structures of FSS also play the role of feeding lines, thus significantly eliminating extra interference compared with conventional feeding networks. We envision that the proposed metasurface may provide new possibilities for the development of an intelligent stealth platform and its antenna applications.

Fully metallic frequency selective surface (FSS) circular polarizer based on cost‐effective chemical etching manufacturing technique

AbstractThis letter presents a fully metallic circular polarizer based on a bandpass frequency selective surface (FSS) that converts linear polarization (LP) to circular polarization (CP) in the Ka‐band. The proposed FSS circular polarizer consists of three cascaded identical perforated metal screens. The Jerusalem slot is used as the element of the FSS circular polarizer to produce an entirely metallic screen with a compact footprint. The Jerusalem slot allows the all‐metallic design to be realized without mechanical issues. A 35 × 35 elements prototype has been designed and manufactured using a cost‐effective chemical metallic etching technique, and performed measurements agree well with the numerical simulations. At broadside direction (), the proposed polarizer operates from 27.5–30.1 GHz, while at the oblique angle of incidence , the operating frequency is reduced to 27.7–29.4 GHz. The manufactured prototype has a low insertion loss (IL), i.e. dB and a good axial ratio performance, i.e. AR ⩽ 2 dB at the desired operating frequency band. Thus, based on a cost‐effective manufacturing technique, the proposed circular polarizer demonstrates an excellent approach to devising all‐metallic FSS polarizers with good IL.