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This letter presents an ultrathin planar bi-layered chiral metasurface which exhibits direction dependent reflection and direction dependent transmission of incident circularly polarized waves within five frequency bands. The five operational frequency bands lie within 5.55-5.78GHz, 6.1-6.23GHz, 10.42-10.68GHz, 11.06-11.17GHz and 12.03-12.18GHz respectively. The metasurface can therefore be used for C, X and Ku microwave band applications. Within the five asymmetric reflection bands, the metasurface acts as a meta-mirror where the handedness of the incident and reflected circularly polarized waves remain unchanged with respect to an observer. The response of the metasurface is stable for incident angles up to 45 degrees for the first four bands and 30 degrees for the final band. This makes it useful even for oblique incidence.

Objective: Hepatic Steatosis is a disorder with high prevalence among obese people. Traditional imaging modalities are more common in hepatic steatosis diagnosis, but they are not suitable for monitoring or treatment evaluation. This study aims at developing a new technique suitable for electromagnetic (EM) tool in the microwave band to differentiate steatotic from non-steatotic liver. Methods: A differential permittivity estimation method for hepatic steatosis detection is proposed. First, the effective permittivity of the right side of the torso is estimated based on the phase difference of electromagnetic waves traveling along symmetric paths within the torso. Then, permittivity modeling and statistical frequency selection are performed to model the estimated values and to extract reliable frequency samples. Finally, the percentage of the difference between the permittivity of the left and right sides of the torso is calculated over the selected samples. Results: The effectiveness of the proposed method is validated using simulated signals and phantom measurements. The analyzed results reveal higher contrast between the average permittivity of the left and right sides of the torso for cases with hepatic steatosis (average contrast of 29.2.

This paper presents the results of modeling attenuators with an attenuation of 1,2 dB and 1,8 dB, based on a harmonic filter with resistive inserts. Resistive inserts were introduced into the low-resistance sections of the harmonic filter, and resistive loops were connected to the high-resistance sections of the filter. An implementation of a 10 dB attenuator based on a quasi-polynomial bandpass filter with losses is proposed. The working frequency band of such attenuators reaches 4 GHz.

In this article, the authors have made an attempt to capture the recent developments taking place in the design of band pass filters (BPF) as a tutorial article. The article deals with the design o...

In this paper, single-layer ultra-Wide Band (UWB) microstrip patch antennas loaded with asymmetrical U-shaped slot in both microwave and millimeter wave applications are presented. These novel antennas cover a fractional bandwidth around 40% in both microwave and millimeter applications. The applications cover the C-band (4–8) GHz, V-band (40–75) GHz, and W-band (75–110) GHz. In addition to that, it is the sole article that cover the bands (5.15–5.825) GHz and (8.025–8.4) GHZ for WiMaX and ITU band applications, respectively. Moreover, it covers three bands for Automotive radar applications within (71–76) GHz, (81–86) GHz, and (92–95) GHz, in addition to further 5G/mm-wave applications at 60 GHz. Each antenna is coaxial fed and implemented on a Roger 5880 substrate with relative dielectric constant of 2.2, thickness of $1.575~mm$ and loss tangent of 0.0009. They operate over the frequency band (5.5–9.5) GHz for microwave band and (55–95) GHz for mm-wave band. To achieve either a notch in other bands or develop a multi-band structure, the conventional ground is replaced by two different structures. The first ground is an array of patches and the other is a mushroom ground. The first ground results in a notch within the band (73–79) GHz while the second one achieves a multi-band within (55–68) GHz and (81–95) GHz. Both antennas are simulated and verified using Finite Difference Time-Domain analysis (FDTD); CST Microwave Studio and Finite Element Method (FEM); Ansoft HFSS. For microwave band, the antenna is fabricated and measured for verification. Concerning the mm-wave version, three different types of ground planes are presented; traditional, periodic structure of patches and mushroom. The structure with periodic patches conducts the same band as the traditional ground plane does. This is a prestep for the design of the notches. The mushroom ground is carried out for multi-band applications. The average gain of the antennas is 7 dB.The measured two dimensional cuts of the radiation pattern, radiation efficiency, and reflection coefficient of the microwave version are presented and are in good agreement with the simulated results while for the mm-wave antenna the same parameters are simulated with two different methods and are in good agreement.

New theoretical and experimental results of microwave acoustic wave propagation in diamond-based multilayer piezoelectric structures (MPS) as “Me1/(Al,Sc)N/Me2/(100) diamond/Me3” and “Me1/AlN/Me2/(100) diamond/Me3” under three metal film depositions, including the change in the quality factor Q as a result of Me3 impact, were obtained. Further development of our earlier studies was motivated by the necessity of creating a sensor model based on the above fifth layered MPS and its in-depth study using the finite element method (FEM). Experimental results on the change in operational checkpoint frequencies and quality factors under the effect of film deposition are in satisfactory accordance with FEM data. The relatively small decrease in the quality factor of diamond-based high overtone bulk acoustic resonator (HBAR) under the metal layer effect observed in a wide microwave band could be qualified as an important result. Changes in operational resonant frequencies vs. film thickness were found to have sufficient distinctions. This fact can be quite explained in terms of the difference between acoustic impedances of diamond and deposited metal films.

New theoretical and experimental results of microwave acoustic wave propagation in diamond-based multilayer piezoelectric structures (MPS) as “Me1/(Al,Sc)N/Me2/(100) diamond/Me3” and “Me1/AlN/Me2/(100) diamond/Me3” under three metal film depositions, including the change in the quality factor Q as a result of Me3 impact, were obtained. Further development of our earlier studies was motivated by the necessity of creating a sensor model based on the above fifth layered MPS and its in-depth study using the finite element method (FEM). Experimental results on the change in operational checkpoint frequencies and quality factors under the effect of film deposition are in satisfactory accordance with FEM data. The relatively small decrease in the quality factor of diamond-based high overtone bulk acoustic resonator (HBAR) under the metal layer effect observed in a wide microwave band could be qualified as an important result. Changes in operational resonant frequencies vs. film thickness were found to have sufficient distinctions. This fact can be quite explained in terms of the difference between acoustic impedances of diamond and deposited metal films.

A simple and universal design principle to realize the generalized Brewster effect (GBE) is proposed. Based on the generalized Kerker effect (GKE), we can realize the GBE for arbitrary polarizations, any incident angles, and any frequencies on the traditional dielectric interface by the destructive interference of various of multipoles. An adjustable metallic meta-surface has been designed to achieve this effect experimentally in the microwave band. By adjusting the suspension height of meta-surfaces above the interface, the incident angles and frequency corresponding to the GBE can be modulated easily. For the two different polarized incident waves, the GBE can be realized at the same frequency and same incident angle, which shows the validity of the GKE. This design principle opens the door for realizing tunable GBE devices that can be applied in many scenarios.

Nowadays, more and more metamaterial absorbers (MMAs) are explored not only in the microwave band but also in terahertz band, but few studies concentrate on metamaterial absorbers which can work in cross-band, that to say, absorb gigahertz (GHz) and terahertz (THz) electromagnetic (EM) waves simultaneously. This paper proposed a design concept of MMA which can realize the absorption in GHz-band and THz-band simultaneously, and designed a cross-band metamaterial absorber (CMMA). The proposed CMMA can achieve three absorption peaks in GHz-band and two absorption peaks in THz-band. The characteristic of simultaneous absorption to GHz and THz waves render the CMMA widely used in multi-band electromagnetic stealth and electronic countermeasures, and the superposition design concept provides a novel idea for designing cross-band absorber.

There is a compelling need for a new form of head scanner to diagnose whether a patient is experiencing a stroke. Crucially, the scanner must be quickly and safely deployable at the site of the emergency to reduce the time between a diagnosis and treatment being commenced. That will help to improve the long-term outlook for many patients, which in turn will help to reduce the high cost of stroke to national economies. This paper describes a novel scanning method that utilises low-intensity electromagnetic waves in the radio frequency/microwave band to detect a stroke-affected region in the brain. This method has the potential to be low cost, portable, and widely deployable, and it is intrinsically safe for the patient and operator. It requires no specialist shielding or power supplies and, hence, can be rapidly deployed at the site of the emergency. That could be at the patient’s bedside within a hospital, at the patient’s home or place of work, or in a community setting such as a GP surgery or a nursing home. Results are presented from an extensive programme of scans of inanimate test subjects that are materially valid representations of a human head. These results confirm that the scanning method is indeed capable of detecting a stroke-affected region in these subjects. The significance of these results is discussed, as well as ways in which the efficacy of the scanning methodology could be further improved.

A novel quasi-Cassegrain metasurfaces (MS) antenna with wide bandwidth operating in 8 GHz band is proposed. Initially, the article demonstrates a complete set of working principles and design approach for the proposed antenna. Then, this antenna is optimised, manufactured, and measured. The profile of the antenna is further reduced by using the reflect-array based on MS, and the gain is improved by loading shielded vias. Note that the second resonant frequency generated from sub-reflector is utilised to extend the bandwidth. The measured results indicate that the antenna achieves the peak gain of 15.9 dBi, impedance bandwidth of 1.07 GHz, and half power beam width of 26° in E plane and 21.5° in H plane. It has a low profile of 26.5 mm (0.71 λ 0 ) and occupies an area of 120 mm × 120 mm (3.20 λ 0 × 3.20 λ 0 ). The article not only completes the antenna operating in 8 GHz band but also provides a reference for the design of the proposed quasi-Cassegrain antenna in microwave band.

In this paper, a systematic study on the growth process of CVD graphene was conducted. Then the optimized growth parameters of CVD graphene were obtained through orthogonal experiment. And the direct corresponding relationship between growth parameters and the sheet resistance of graphene band was given by parametric comparison experiment and formula fitting. The result in this paper established a bridge between basic research and application of graphene in microwave band.

Spoof LSP (Localized Surface Plasmon) is a great advance in metamaterials, expanding the LSP resonance from optical band into microwave band. It will yield amazing outcomes by integration with flexible electronics, wearable electronics and nanophotonics. Here, an ultrathin and flexible spoof LSP prepeared by layer-by-layer (LBL) assembly of gold nanoparticles was demonstrated. The LSPR effects in microwave band was assembly-induced and the electric resonance component disappeared, which is significantly different from that of the spoof LSPs by bulk metal. It was thought and proved by simulation to be relative with the special micro-structure of the gold nanoparticle assemblies. Furthermore, the spoof LSP by gold nanoparticles was flexible and showed a strong relationship between the resonance frequency and the curvature degree of the spoof LSP, meaning that the LSP resonance can be modulated by the deformation of the spoof LSP. We believed that these results could deepen understanding about the spoof LSPs and widen the application in multiple areas.

The circular dichroism resonator (CDR) can produce spin selective absorption for left-handed circularly polarized (LCP) and right-handed circularly polarized (RCP) waves. However, in the microwave band, the previously proposed CDRs only absorb designated CP waves and lack versatility in practical applications. Here, we propose a switchable CDR based on a pair of PIN diodes. It switches between the left-hand and right-hand CDR modes through the alternate ON-OFF of two PIN diodes. The left-hand CDR absorbs LCP waves and converts RCP waves into LCP waves. The opposite is true for the right-hand CDR. The thickness of the switchable CDR is one-tenth of the working wavelength, which is suitable for integrated manufacturing.

In this paper, a nested square-shape dielectric resonator (NSDR) has been designed and investigated for antenna applications in the microwave band. A solid square dielectric resonator (SSDR) was modified systematically by introducing air-gap in the azimuth (ϕ-direction). By retaining the square shape of the dielectric resonator (DR), the well-known analysis tools can be applied to evaluate the performance of the NSDR. To validate the performance of the proposed NSDR in antenna applications, theoretical, simulation, and experimental analysis of the subject has been performed. A simple microstrip-line feeding source printed on the top of Rogers RO4003 grounded substrate was utilized without any external matching network. Unlike solid square DR, the proposed NSDR considerably improves the impedance bandwidth. The proposed antenna has been prototyped and experimentally validated. The antenna operates in the range of 12.34GHz to 21.7GHz which corresponds to 56% percentage bandwidth with peak realized gain 6.5dB. The antenna has stable radiation characteristics in the broadside direction. A close agreement between simulation and experimental results confirms the improved performance of NSDR in antenna applications.

In this paper, a series of broadband absorbers with different surface resonance structures fabricated by EHD-printed silver meshes on flexible and transparent substrates are introduced. By designing different resonance structures, we can obtain flexible and transparent broadband absorbers in different wavebands. In the microwave band, simulation results have shown that the absorber designed by printing the double-ring frequency selective surface (FSS) on the polyethyleneterephthalate (PET) substrate can achieve >80% absorption in (11.8-41.2) GHz, completely covering Ku, K and Ka bands. The millimeter-wave absorber fabricated by printing a single layer silver mesh structure on the PET substrate shows >80% absorption in the range of (62.5-110.6) GHz, completely covering the W-band. In the Terahertz band, the flexible transparent absorber with sliver grid structure showed >90% absorption in (98–353) GHz range.

We reported an analog of electromagnetically induced transparency (A-EIT) featured by double transparent peaks in the spectrum. The A-EIT is realized by double-layered metasurface which consists of spoof localized surface plasmons (S-LSP) and cut-wire (CW)-square rings (SR) hybrid. Electric and magnetic S-LSP are excited as bright and dark modes respectively then couple with resonant modes of CW and SR simultaneously to achieve multiple A-EIT. Two bright modes of the electric S-LSP and SR are excited by external electric field directly that produce a bright-bright mode A-EIT. Moreover, the magnetic S-LSP, which cannot be excited by external field directly, is excited through near field coupling from CW, inducing another bright-dark mode A-EIT. Theoretical analysis with corresponding experiment in microwave band are introduced for better insights into physical essence of the double-peaks A-EIT.

Application of multi-frequency radiolocation allows to expand essentially received signals spectrum that increases amount of a target (object) classification identifiers including thermal portraits for radiometric measurements. In this paper it is represented a prototype of measuring radiometric unit allowing to carry out simultaneously contactless radiometric research of liquids in two wavelength ranges: 8-mm and 3-mm. It is developed the method of definition of parameters of capacity (container) where liquids are placed. It is estimated an influence of caustics appearing in case of waves reflections from internal wall of container and also on quality factor, attenuation coefficient and relative factor of container which are distantly measured. In two frequency ranges there are carried out researches of two water solutions and oil processing products (gasoline, dissolvents, diesel fuel). It is shown the liquids with close thermal portraits in identical frequency band due to close physical-chemical parameters, can have different thermal portraits obtained in different frequency bands reflecting dispersion properties of the liquids and they can be used for liquids identification visually or in case of received data processing.

The information content of the coupled impedance of linear antenna arrays in the microwave band as a function of the sounding conditions and electrophysical properties of the monitored horizontally-stratified media is analyzed. The applicability of the method of wideband sounding for diagnostics of stratified media from the measured impedance of linear antenna arrays is estimated. The arrangement geometry of the transceiver linear antennas is optimized; new algorithms for remote control and detection of localized inhomogeneities of dielectric and poorly conducting media are proposed.

In this study, Co0,7Zn1,3W powders were synthesized and investigated at the microwave region. The solid-state reaction method and self-propagating high-temperature synthesis were used to production of the two kinds of hexaferrite powders. The high-frequency magnetic properties under temperature effect have been studied. It is show, that there is a nonlinear dependence on temperature within the 0 – +40 °C temperature range.

In this letter, a high-gain and low-profile quasi-Cassegrain antenna based on metasurfaces (MS) is proposed. Thanks to the structure of the dual reflectors and the phase compensation technology achieved by MS, the proposed antenna presents a balance between high gain and low profile. This antenna achieves the peak gain of 13.7 dBi, sidelobe level less than −19 dB, and half-power beamwidth of 38° ( H -plane) and 28° ( E -plane). At the same time, it has a low profile of 12.6 mm (0.244 λ 0) and occupies an area of 132 mm × 132 mm (2.55 λ 0 × 2.55 λ 0). The proposed quasi-Cassegrain antenna in this letter provides an alternative for the high-gain and low-profile antenna and also enriches the applications of MS in the microwave band.

In this paper, we investigate the possibility of adopting millimeter-wave technology with passive radio-frequency identification based on backscattered signals to perform tag localization with a single reader equipped with high-directivity beamsteering antennas. The numerical results concerning the considered architecture show that, despite the high path-loss at 60 GHz, it is possible to attain reliable tag identification and localization. This is allowed by the less stringent requirements in terms of transmitted energy with respect to its counterpart using the ultrawide bandwidth technology in the microwave band and the available higher antenna gain.