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Pathology is an important branch of science in the diagnosis and treatment of several diseases. In cancer diseases, serious investigations have been made about the course of the diseases. A report that is essential for both the patient and the doctor is prepared by the pathologists as a result of a detailed cellular examination. These reports contain information about the disease. Access duration to these reports, which affects the form and duration of the treatment, is extremely important today. It is possible to shorten this period with systems using antenna technologies. The pathological breast tissue samples have been examined by using horn antenna structures with high gain in this study. Dual identical horn antennas have been placed opposite each other as receivers and transmitters in the measurement setup at 24 GHz. Measurements of normal and cancerous breast tissues have been made, and the normalization process has been applied to the measured scattering parameters. The different values between normal and cancerous breast tissues have been shown with this process. The normalized values are compared with other analyzed values. According to the results obtained, the percentage of normalized values for transmission is much more effective and meaningful than other results. [ABSTRACT FROM AUTHOR]

This article introduces an innovative methodology for measuring the impedance of RFID (Radio Frequency Identification) chips. The primary objective is to develop a technique that enables impedance measurement across a range of frequencies, centered around the critical operational frequency of RFID systems, specifically 13.56 MHz. Unlike conventional methods, which typically focus solely on the impedance at 13.56 MHz, this approach utilizes the reflection coefficient of the device under test (DUT) to measure impedance over a broader frequency spectrum. This spectrum encompasses the frequencies within the ISO14443 communication bandwidth. The excitation signal is carefully selected to closely mimic an actual RFID communication frame. The experimental results demonstrate the feasibility of this method by comparing the impedance measurements of passive component pairs against those obtained using a vector network analyzer (VNA). Subsequently, the technique is applied to an RFID chip, underscoring its practical applicability and accuracy. [ABSTRACT FROM AUTHOR]

New SPICE-compatible circuit models of a multiport are presented here that are suitable for the frequency-domain and time-domain analyses of hybrid systems containing linear distributed elements and possibly non-linear lumped elements. Distributed elements models are based on scattering parameters with potentially complex reference impedances, which are not necessarily equal for all ports. Both exact and approximated (lumped) models are proposed. The scattering parameters are directly taken as the model element values in the former case. In the latter case, the model element values are equal to the real and imaginary parts of the poles and residues of the rational approximation. The models comprise a multiport (with an admittance matrix numerically equal to the modeled scattering matrix or approximating it) equipped with a pair of coupled impedances at each port. A few examples validate the proposed approach and prove its efficiency in terms of matrix size and analysis time compared to some selected commercial counterparts. [ABSTRACT FROM AUTHOR]

Two-particle correlations are presented for KS0, Image 1, and Image 2 strange hadrons as a function of relative momentum in lead-lead collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The dataset corresponds to an integrated luminosity of 0.607nb−1 and was collected using the CMS detector at the CERN LHC. These correlations are sensitive to quantum statistics and to final-state interactions between the particles. The source size extracted from the KS0KS0 correlations is found to decrease from 4.6 to 1.6fm in going from central to peripheral collisions. Strong interaction scattering parameters (i.e., scattering length and effective range) are determined from the Image 3 and Image 4 (including their charge conjugates) correlations using the Lednický–Lyuboshitz model and are compared to theoretical and other experimental results.

In this paper, a method is presented to design and implement ultra-wideband phase shifters, in frequency ranges higher than 10 GHz, with fractional bandwidth near a hundred percent. The phase shifter is constructed from microstrip transmission lines and short circuit stubs. In comparison with conventional phase shifters which are composed of microstrip coupled lines and multilayer structures, the proposed phase shifter has advantages from the implementation and fabrication viewpoint. The design and optimization method is in such a way that arbitrary phase shift, source and load impedances may be considered in the design. To optimize the circuit dimension, a computer code is written, and two design examples are considered. The computer code is based on closed form equations for microstrip transmission lines and available circuit models for it and utilizes microwave network equations. Its results are then improved with electromagnetic full-wave packages to consider the parasitic effects of microstrip T-junctions. Two design cases are included, in the first design, the case of a 45 degrees phase shifter with a standard 50 ohms source and load impedances is investigated. In the second design case, the case of a 90 degrees phase shifter with 50 ohms input impedances and 75 ohm non-standard output impedances is considered. By observing the full-wave simulation results as well as the fabrication and measurement results in these examples, it is clear that the design goals are highly satisfied by this method.

InGaAs detection systems have been increasingly used in the aerospace field, and due to the high signal-to-noise ratio requirements of short-wave infrared quantitative payloads, there is an urgent need for methods for the rapid and precise evaluation and the optimal design of these systems. The rigid-flex printed circuit board (PCB) is a vital component of InGaAs detectors, as its grid ground plane design parameters impact parasitic capacitance and thus affect weak infrared analog signals. To address the time-intensive and costly nature of design optimization achieved with simulations and experimental measurements, we propose an innovative method based on a neural network to predict the scattering parameters of rigid-flex boards for InGaAs detection links. This is the first study in which the effects of rigid-flex boards on weak infrared detection signals have been considered. We first obtained sufficient samples with software simulation. A backpropagation (BP) neural network prediction model was trained on existing sample sets and then verified on a rigid-flex board used in a crucial aerospace short-wave infrared quantitative mission. The model efficiently and accurately predicted high-speed interconnect scattering parameters under various rigid-flex board grid plane parameter conditions. The prediction error was less than 1% compared with a 3D field solver, indicating an overcoming of the iterative optimization inefficiency and showing improved design quality for InGaAs detection circuits. [ABSTRACT FROM AUTHOR]

Context. Microwave stub filters are widely used in radio engineering and telecommunication systems, as well as in technical information protection systems due to simplicity of design, possibility of realization in microstrip design and manufacturability in mass production. For synthesis of stub filters nowadays traditional methods based on transformation of low-frequency prototype filters on LC-elements into filtering structures on elements with distributed parameters are used. The transformations used are approximate and provide satisfactory results for narrowband stub filters. In this connection there is a necessity in development of direct synthesis methods for stub filters, excluding various approximations and providing obtaining of amplitude-frequency characteristics with optimal shape for any bandwidths. Objective. The purpose of the study is to develop a method for direct synthesis of stub band-pass filters and low-pass filters with Chebyshev amplitude-frequency response in the passband. Method. The procedure of direct synthesis includes the formulation of relations for filter functions of plume structures, selection of approximating functions of Chebyshev type for filter functions and formation of a system of nonlinear equations for calculation of parameters of filter elements. Results. A method for the direct synthesis of stub bandpass and lowpass filters with Chebyshev response is developed. Conclusions. Scientific novelty of the work consists in the development of a new method of direct synthesis of l stub filters. The method, in contrast to approximate traditional methods of synthesis of microwave filters, is exact, and the obtained solutions of synthesis problems are optimal. The experiments confirmed the performance of the proposed method and the optimality of the obtained solutions. Prospects for further research suggest adapting the method to the synthesis of filter structures with more complex resonators compared to stubs. [ABSTRACT FROM AUTHOR]

The heuristic homogenization approach is intensively employed to characterize electromagnetic metamaterials (MMs). The effective parameters are extracted within this framework using the Nicolson–Ross–Weir (NRW) method. Special attention must be devoted to handling this procedure because of the branch ambiguity issue affecting it, i.e., the lack of uniqueness in the evaluation of the effective refractive index n e f f rooted in the use of the multivalued complex logarithm to invert the Airy–Fresnel relation. Over the years, several techniques based on the phase-unwrapping approach have been introduced, but without any theoretical justification. In this paper, we aim to clarify the theoretical connection between the phase unwrapping method and the analytic continuation theory framework. Furthermore, three-phase-unwrapping approaches, which descend directly from the theory we discussed, are compared to identify which approach is best suited to reconstruct the complex refractive index of metamaterials when the NRW method is applicable. [ABSTRACT FROM AUTHOR]

In microwave electronics, the power gains of a linear two-port are customarily defined as the ratio of an output port and input port power, where such powers are intended either as operational or as available. Two input and two output powers are thus introduced, with four possible combinations of output/input power ratios, but only three are practically exploited, the well-known operational power gain, available power gain, and transducer power gain. In the present paper, we provide a comprehensive review of gain definitions (including the less commonly exploited added-power gains) and finally consider the missing fourth element (defined as the ratio of the output available power and of the input operational power), derive a few mathematical properties of it, both in the general and in the unilateral case, and ultimately justify the reason why this fourth gain G 4 which, following the suggestion of an anonymous reviewer, we will call apparent power gain, G app , has little interest in the optimization of the power transfer between the generator and the load. Nevertheless, the definition and analysis of G app , besides being formally useful to complete the gain family, may yield a deeper insight into the very nature of power transfer optimization in a loaded two-port. [ABSTRACT FROM AUTHOR]

Carbon-based materials, such as graphene, exhibit interesting physical properties and have been recently investigated in sensing applications. In this paper, a novel technique for glucose concentration correlation with the resonant frequency of a microwave resonator is performed. The resonator exploits the variation of the electrical properties of graphene at radio frequency (RF). The described approach is based on the variation in transmission coefficient resonating frequency of a microstrip ring resonator modified with a graphene film. The graphene film is doctor-bladed on the ring resonator and functionalised in order to detect glucose. When a drop with a given concentration is deposited on the graphene film, the resonance peak is shifted. The graphene film is modelled with a lumped element analysis. Several prototypes are realised on Rogers Kappa substrate and their transmission coefficient measured for different concentrations of glucose. Results show a good correlation between the frequency shift and the concentration applied on the film. [ABSTRACT FROM AUTHOR]

Recent advances in embedded antenna and sensor technologies for 5G communications have galvanized a response toward the investigation of their electromagnetic performance for urban contexts and civil engineering applications. This article quantitatively investigates the effects of material loading on an evolved antecedent hexagonal complementary split-ring resonator (CSRR)-loaded antenna design through simulation and experimentation. Optimization of the narrowband antenna system was first performed in a simulation environment to achieve resonance at 3.50 GHz, featuring an impedance bandwidth of 1.57% with maximum return loss and theoretical gain values of 20.0 dB and 1.80 dBi, respectively. As a proof-of-concept, a physical prototype is fabricated on a printed circuit board followed by a simulation-based parametric study involving antenna prototypes embedded into Ordinary Portland Cement pastes with varying weight percentages of iron(III) oxide inclusions. Simulation-derived and experimental results are mutually verified, achieving a systemic downward shift in resonant frequency and corresponding variations in impedance matching induced by changes in loading reactance. Finally, an inversion modeling procedure is employed using perturbation theory to extrapolate the relative permittivity of the dielectric loaded materials. Our proposed analysis contributes to optimizing concrete-embedded 5G antenna sensor designs and establishes a foundational framework for estimating unknown dielectric parameters of cementitious composites. [ABSTRACT FROM AUTHOR]

This paper focused on propagation characteristics of a single mode supporting waveguide enclosed by metallic sidewalls periodically loaded with lossless single negative (SNG) metamaterial slabs along axial direction. The gap between two successive SNG slabs is filled with a double positive (DPS) material. For the analysis, the periodic structure is assumed having symmetric unit cell (UC) and simplified as a two-port network which is one-half of the symmetric UC. Scattering parameters (S-parameters) are defined by even/odd mode analysis of the symmetric UC, and then the total S-parameters are calculated by solving the cascade connection of N unit cells. Eigenvalue equations are also obtained to explicit the solutions of band edge and pass/stopband diagrams in the microwave regime. Since a SNG can be either epsilon-negative (ENG) or mu-negative (MNG), S-parameters and dispersion behavior are illustrated with numerical examples and discussed for each periodic structure constructed with ENG or MNG slabs. [ABSTRACT FROM AUTHOR]

Interconnects have become a major obstacle in chip scaling. Spoof surface plasmon polariton (SSPP) modes have gained attention for their ability to manipulate light beyond diffraction limits at a given frequency, leading to SSPP interconnects. This article investigates the transmission characteristics of SSPP interconnect pairs placed side by side in the terahertz frequency range with comprehensive performance analysis. The proposed SSPP waveguide pair exhibits a maximum transmission coefficient of around −0.05 dB in the −3 dB band in the terahertz frequency range. Due to field confinement near the metal–dielectric interface, energy remains confined for the designed SSPP interconnect pair system. The proposed SSPP structure shows several bands in the terahertz frequency range, whereas conventional interconnects shows almost zero transmission at such frequencies. Additionally, the effect of geometric parameters on transmission coefficients (S 21 ) and coupling coefficients (S 41 ) has been investigated. Moreover, it has been shown that the bandwidth, as well as the upper cutoff frequency, can be tuned by varying the geometric parameters such as groove height, groove width and groove density. Since global interconnects undergo bending in actual circuits during distant data transmission on chips, geometric mismatches may occur between adjacent pairs of SSPP interconnects. Hence, it has also been examined how bending and mismatches affect transmission and coupling coefficients. Several SSPP schemes have been simulated, among which the best performance is obtained with 2 μ m mismatch in groove height. For this optimized design, two corrugated metal interconnects are considered with groove heights of 20 μ m and 22 μ m, respectively, a groove width of 3 μ m, a period of 20 μ m, and the number of grooves at 50. For this particular configuration, an ultra-wide passband is found having a bandwidth of almost 400 GHz, with a signal reflection of below −12 dB and little insertion loss of ∼−1.43 dB. [ABSTRACT FROM AUTHOR]

This paper presents a radio-frequency (RF) antenna as a sensor to detect Horseradish peroxidase (HRP). At the core of the proposed approach is a graphene film deposited on a stub connected to an RF antenna. The graphene film is doctor bladed on the stub. The film is then properly chemically functionalized in order to detect the presence of Horseradish peroxidase (HRP). We validate the proof-of-concept operation of HRP concentration detection by measuring the frequency shift of the reflection coefficient of the antenna using very small concentration of HRP ( 0.03 mM to 0.6 mM). [ABSTRACT FROM AUTHOR]

InGaAs detection systems have been increasingly used in the aerospace field, and due to the high signal-to-noise ratio requirements of short-wave infrared quantitative payloads, there is an urgent need for methods for the rapid and precise evaluation and the optimal design of these systems. The rigid-flex printed circuit board (PCB) is a vital component of InGaAs detectors, as its grid ground plane design parameters impact parasitic capacitance and thus affect weak infrared analog signals. To address the time-intensive and costly nature of design optimization achieved with simulations and experimental measurements, we propose an innovative method based on a neural network to predict the scattering parameters of rigid-flex boards for InGaAs detection links. This is the first study in which the effects of rigid-flex boards on weak infrared detection signals have been considered. We first obtained sufficient samples with software simulation. A backpropagation (BP) neural network prediction model was trained on existing sample sets and then verified on a rigid-flex board used in a crucial aerospace short-wave infrared quantitative mission. The model efficiently and accurately predicted high-speed interconnect scattering parameters under various rigid-flex board grid plane parameter conditions. The prediction error was less than 1% compared with a 3D field solver, indicating an overcoming of the iterative optimization inefficiency and showing improved design quality for InGaAs detection circuits.

An MLP-ELM-based modeling method for GaN HEMT small-signal properties is proposed. First, a hybrid parameter extraction method is developed based on the GWO to solve the problem of in-accurate extraction of 20-element equivalent circuit parameters; then the S-parameters obtained from the model are combined with MLP-ELM to establish an accurate empirical model, which effectively solves the problem that the equivalent circuit model cannot represent the small signal properties in the multi-bias range; finally, an empirical-based small signal model is developed with MLP-ELM, The simulation results show that the proposed model has high precision, is effective in the whole bias range and has the generalization ability that the equivalent circuit model lacks. [ABSTRACT FROM AUTHOR]

We present the broadband transmission-reflection meniscus-removal method for liquid characterization in a semi-open rectangular waveguide. The algorithm utilizes 2-port scattering parameters measured with a calibrated vector network analyzer for three states of the measurement cell: empty and filled with two liquid levels. The method enables the mathematical de-embedding of a symmetrical sample of a liquid, not distorted with a meniscus, and provision of its permittivity and permeability, as well as its height. We validate the method for propan-2-ol (IPA), a 50% aqueous solution of IPA, and distilled water in the Q-band (33–50 GHz). We investigate typical problems for in-waveguide measurements, such as phase ambiguity. [ABSTRACT FROM AUTHOR]

The advancement of high-power microwave technology has indeed brought about the possibility of E-bombs, also known as electromagnetic pulse (EMP) bombs. These weapons emit an electromagnetic pulse that can disable electrical circuitry within a specific radius. As the frequency spectrum becomes more congested with various technologies operating in similar frequency bands, the need for shielding against interference becomes crucial. One promising solution is the use of conductive concrete, which is created by incorporating conductive components into a traditional concrete mixture. This conductive concrete has shown excellent shielding properties and improved electrical characteristics. To assess and quantify its effectiveness, the relative complex permittivity of the concrete mixture needs to be estimated. In this paper, the authors propose a method for estimating the relative complex permittivity of the concrete mixture. This was achieved by measuring the scattering parameters of concrete samples using a rectangular waveguide within the C-band frequency range. The scattering parameters provide valuable information about how electromagnetic waves interact with the concrete. A dielectric mixing model was developed to determine the relative complex permittivity. This model takes into account the volume percentage and the dielectric properties of the individual constituents present in the concrete mixture. By applying this model and obtaining the complex permittivity of the mixture, it becomes possible to calculate the required thickness of the conductive concrete mix needed to achieve the desired levels of electromagnetic attenuation and shielding.

As one of the important components of internet of things (IOT) systems, radio frequency identification (RFID) tags need to be improved in terms of power consumption, size reduction and coding capacity. In conventional methods, designers focus on optimizing resonators, but by focusing on the use of phase coding, a new method can be presented that results in a tag with smaller dimensions and more coding capacity. Hybrid encoding for RFID is based on the phase coding by changing the position of the resonator in the chipless RFID tag. In this paper a C-shaped resonator is proposed to design a chipless tag on the Rogers RT/duroid 5880 laminates. This method proposes different phase values in the resonance frequency as separate codes. The difference between the phases ( $\Phi$ ) of the scattering parameters S11 and S22 is measured to show the effect of position varying of the proposed C-shaped resonator. With the three different values of $\Phi $ at the resonance frequency, the proposed RFID tag creates codes 0, 1 and 2, in comparison with the conventional structures that create codes 0 and 1 only, based on the presence or absence of a transition zero at the resonance frequency. The proposed structure was designed, fabricated and measured and measurement results validate this method. Accordingly, an RFID tag with five C-shaped resonators is proposed, where the simulation results of its $3^{5}=243$ different states are presented in this paper.

In the design of amplifier stages based on unconditionally stable linear active two-ports, the amplifier gain can be maximized through simultaneous conjugate matching with passive loads at the input and output ports. Conversely, the optimization of linear amplifiers based on conditionally stable active devices requires a trade-off between gain, stability margin, input/output port mismatch and (for low-noise amplifiers) noise figure. Exploiting potentially in-band unstable devices can be advantageous in the design of open-loop low-noise amplifiers, since the in-band stabilization with input resistors is well known to negatively affect the amplifier minimum noise figure. Within this framework, the article derives a lower bound to the input and output mismatch of non unconditionally stable linear two-ports. The minumum mismatch is shown to only depend, in a simple way, on the stability factor $K$ and on the assumed mismatch ratio between the two ports. The minimum mismatch condition can be implemented by cascading the active, potentially in-band unstable two-port with two (input and output) reactive matching sections. The application of the theory to the design of low-noise amplifier open-loop stages based on conditionally stable active devices is discussed through CAD examples.

The simplest Micro-Ring Resonator consists of an input–output directional coupler connected into itself through a feedback loop. We show that a magneto-optical coupler exhibiting a nonreciprocal phase shift is enough to render the whole structure nonreciprocal, even with an otherwise reciprocal loop. We illustrate this effect by considering a planar (slab) coupler made of bigyrotropic waveguides submitted to a suitable external magnetization; its scattering parameters are derived analytically in the frame of Coupled Mode Theory. Including the modal dispersion, it is possible to adjust the dimensions and/or the operating wavelength in order to design very specific regimes, either in absorption, amplification or emission, from a rather trivial unidirectional behavior to the subtler case of well-balanced interdigitated frequency combs—circulating both ways, but separated by exactly one half of a Free Spectral Range. [ABSTRACT FROM AUTHOR]

This paper presents a new methodology for detecting bare rough soil in non-urban areas using synthetic aperture radar data. Our approach involves matching the covariance/coherence matrix to the extended Bragg (xBragg) model. Our method uses automatic OTSU's thresholding based on roughness angles histogram to determine output classes and avoid complex calculations, making it suitable for onboard computing. The procedure is suitable for a range of soil roughness but not for highly specular surfaces. The performance of the suggested methodology was evaluated using simulated data and real L- and P-band SAR datasets from two different sites with various features. Our results demonstrate the effectiveness of the method for rough agricultural and natural surfaces, with good performance and a success rate of up to about 95 % across a wide range of roughness values from 0 ∘ to 65 ∘ . [ABSTRACT FROM AUTHOR]

In this paper, we propose a machine-based classification technique using the scattering parameters obtained using a wearable wideband textile antenna to diagnose breast tumors. The breast phantom is formed following the dielectric properties of the human breast tissues and characterized to ensure the resemblance with a actual tissue model for the range of frequencies from 3 to 10 GHz. A biocompatible textile antenna is fabricated and embedded on an artificial breast phantom model to capture the variation of the reflection coefficient S 11 and the transmission coefficient S 21 for frequencies 3–10 GHz for different locations and sizes of tumors within the phantom model. Support vector machine is used to classify the healthy tissues from the malignant tumors based on the variation of the scattering parameters owing to the variation of the dielectric characteristics of the breast phantom model. The proposed method offers 84% and 89% accuracy while using S 11 and S 21 parameters alone for the analysis. However, the results further improve up to 93% as a combination of S 11 and S 21 signals is considered. [ABSTRACT FROM AUTHOR]

The threat of chip-level tampering and its detection has been widely researched. Hardware Trojan insertions are prominent examples of such tamper events. Altering the placement and routing of a design or removing a part of a circuit for side-channel leakage/fault sensitivity amplification are other instances of such attacks. While semi- and fully-invasive physical verification methods can confidently detect such stealthy tamper events, they are costly, time-consuming, and destructive. On the other hand, virtually all proposed non-invasive side-channel methods suffer from noise and, therefore, have low confidence. Moreover, they require activating the tampered part of the circuit (e.g., the Trojan trigger) to compare and detect the modifications. In this work, we introduce a non-invasive post-silicon tamper detection technique applicable to different classes of tamper events at the chip level without requiring the activation of the malicious circuit. Our method relies on the fact that physical modifications (regardless of their physical, activation, or action characteristics) alter the impedance of the chip. Hence, characterizing the impedance can lead to the detection of the tamper events. To sense the changes in the impedance, we deploy known RF tools, namely, scattering parameters, in which we inject sine wave signals with high frequencies to the power distribution network (PDN) of the system and measure the “echo” of the signal. The reflected signals in various frequency bands reveal different tamper events based on their impact size on the die. To validate our claims, we performed measurements on several proof-ofconcept tampered hardware implementations realized on FPGAs manufactured with a 28 nm technology. We further show that deploying the Dynamic Time Warping (DTW) distance can distinguish between tamper events and noise resulting from manufacturing process variation of different chips/boards. Based on the acquired results, we demonstrate that stealthy hardware Trojans, as well as sophisticated modifications of P&R, can be detected.

The heuristic homogenization approach is intensively employed to characterize electromagnetic metamaterials (MMs). The effective parameters are extracted within this framework using the Nicolson–Ross–Weir (NRW) method. Special attention must be devoted to handling this procedure because of the branch ambiguity issue affecting it, i.e., the lack of uniqueness in the evaluation of the effective refractive index neff rooted in the use of the multivalued complex logarithm to invert the Airy–Fresnel relation. Over the years, several techniques based on the phase-unwrapping approach have been introduced, but without any theoretical justification. In this paper, we aim to clarify the theoretical connection between the phase unwrapping method and the analytic continuation theory framework. Furthermore, three-phase-unwrapping approaches, which descend directly from the theory we discussed, are compared to identify which approach is best suited to reconstruct the complex refractive index of metamaterials when the NRW method is applicable.

This paper examines the effect of finger fat pad thickness on the accuracy performance of complementary split-ring resonator (CSRR)-based microwave sensors for non-invasive blood glucose level detection. For this purpose, a simplified four-layer Cole–Cole model along with a CSRR-based microwave sensor have been comprehensively analyzed and validated through experimentation. Computed scattering parameter (S-parameter) responses to different fat layer thicknesses are employed to verify the concordance of the studied model with the measurement results. In this respect, a figure of merit (FM) based on the normalized squared difference is introduced to assess the accuracy of the considered Cole–Cole model. We have demonstrated that the analyzed model agrees closely with the experimental validation. In fact, the maximum error difference for all five fingertips does not exceed 1.73 dB over the entire frequency range of interest, from 1 GHz to 4 GHz. [ABSTRACT FROM AUTHOR]

This research discusses about the effect of adding high content cashew shell biochar (CSB) nanoparticle onto the carbon fibre–reinforced epoxy resin composite in electromagnetic interference (EMI) shielding behaviour. The primary goal of this research was to study the EMI shielding behaviour of CSB particle addition in carbon-epoxy composite at elevated frequency ranges up to 18 GHz. The shielding epoxy composites were prepared via hand layup method followed by characterized in accordance to ASTM standards. It is noted that the addition of CSB particle increased the mechanical properties of carbon-epoxy composite up to 226 and 298 MPa in tensile and flexural properties of composite designation CS4. The scattering parameters of tested composites showed highest reflection, multi-reflection and absorption behaviour for high CSB content in composite. It is further noted that the shielding effect increased with the volume of CSB particle. A highest shielding of − 48.6 dB was observed for composite designation CS5 at 18 GHz. These EMI shielding behaviours improved biochar-epoxy composites which could be used in radar, telecommunication, defence and signal processing devices where the effect of interference needs to be reduced. [ABSTRACT FROM AUTHOR]

In this brief, we propose a dual-mode power divider (PD) based on slow-wave SIW structure. The slow-wave structure is integrated to the SIW for obtaining filtering feature and a multifunctional PD with both in-phase and out-of-phase responses is designed by adopting different feeding mechanism. Then, the presented PD is applied to build a monopulse antenna with simple structure. A tapered patch is inserted into the center of the PD and excited through coupling for endfire radiation. When the PD works in in-phase mode, the even-mode E-field can be obtained at the end of radiator, resulting in the difference beam. When the PD works in out-of-phase mode, the odd-mode E-field can be obtained at the end of radiator, leading to the sum beam. The proposed monopulse antenna was fabricated and measured for validating the feasibility of the design approach. Measured results indicate that the sum and difference beams of the antenna are both realized in the same frequency range. This approach provides a straightforward way to design monopulse antenna, which can be applied in radar detection and tracking. [ABSTRACT FROM AUTHOR]

This brief introduces a compact S-parameter model of the two-port 90° N-Path circuit within the vicinity of the clock frequency. Transfer and reflection coefficients, which manifest the circuit filtering properties and the non-reciprocal phase shifting, are derived for a circuit that utilizes ideal switches and then extended to account for transistor parasitics. New simplified equations for parasitic phase and frequency shifts, which are of interest in the design of circuits such as electronic circulators, are proposed. Good agreement is demonstrated between the analytic coefficients and simulation results of behavioral 4-path as well as 65-nm NMOS 8-path circuits, both excited by a 1 GHz clock. The proposed expressions are utilized to compare an electronic circulator that includes an analytic 8-path model versus one that employs an NMOS switched circuit. Agreement of better than 0.2dB is demonstrated for insertion losses whereas isolation results differ by less than 2 dB over an 80 MHz bandwidth centered at 980 MHz. [ABSTRACT FROM AUTHOR]

This brief offers a compact, tightly-coupled, self-decoupled vias-based multiple-input multiple-output (MIMO) antenna pair with a common ground for a 5G system. The projected design comprises modified T-shaped tightly-coupled antenna elements. It is effortlessly helping to achieve sound decoupling across the desired band without using any extra decoupling circuit between the elements. It is revealed that the structure of the self-decoupled MIMO antenna tunes the inductive and capacitive (hybrid) effect of elements, which helps to achieve the decoupling of antenna elements. A relevant equivalent circuit model for coupled and decoupled MIMO antenna is proposed to validate the insight operation of this proposed theory. The hybrid tuning among the MIMO antenna elements reduces the coupling effect mutually by modifying the antenna shapes. The proposed self-decoupled MIMO antenna pair demonstrates low mutual coupling across the 5G NR frequency bands: n48 and long-term evolution (LTE) band 42/52 (3.2–3.6 GHz) with good diversity characteristics. Moreover, the one proposed design structure can offer dual-band self-decoupling features. The proposed structure provides 3.2-3.6GHz and 3.95-4.115GHz frequency bands. This structure can be optimize further to achieve dual-band/ wideband resonance in the design. [ABSTRACT FROM AUTHOR]

This brief proposes a novel decoupling method based on metallic sheets to improve inter-port isolation in dual-port single-element multiple-input-multiple-output (MIMO) dielectric resonator antenna (DRA) systems. Two different structures, including an H-plane and an E-plane decoupled MIMO arrangement, have been investigated. The exploitation of metallic sheets can significantly impact the electromagnetic (EM) field distribution inside the dielectric resonator (DR) and restrict the strongest portion of the EM energy couple to the nearby slot. As a result, inter-port isolation can be improved significantly. As the single DR element is used and metallic sheets are embedded within the element, no additional footprint is required, making the MIMO antenna arrangements compact and simple. The outcomes convey a maximum enhancement in the inter-port isolation of the H-plane decoupled MIMO arrangement is about 23.45 dB, while that of the E-plane decoupled MIMO arrangement is about 17.08 dB across the operating frequency band. [ABSTRACT FROM AUTHOR]

This letter proposes a miniaturized frequency selective rasorber (FSR) based on parallel-plate capacitors that can be applied in antenna systems to delay the appearance of grating lobes. Compared with traditional solutions, the lossy-layer unit-topology is rearranged to balance a more efficient capacitor C1, fewer resistive lumped elements, and a large inductance L1 in series. Furthermore, the lossless layer is constructed using a third-order frequency selective surface with parallel-plate capacitors. These approaches achieve a rasorber unit size of only 0.035λL, where λL is the wavelength of the lowest absorption frequency. Under normal incidence, the 1 dB transmission band with a bandwidth of 40.9% is obtained at 6 GHz, whereas an absorption rate of over 90% covers 1.5 to 4.05 GHz. Moreover, the FSR exhibits high stability for the dual-polarization and oblique incidence up to 30°. Prototypes were fabricated and measured, verifying the feasibility of the miniaturized design. [ABSTRACT FROM AUTHOR]

This letter presents a planar inverted-F antenna (PIFAs) system for Wireless Fidelity 6 (Wi-Fi 6) and Wi-Fi 6E applications with compact size and high isolation. To realize decoupling in a guided way, single-mode structure is proposed based on common mode and differential mode theory. For the demonstration, the mutual coupling between two back-to-back asymmetric PIFAs was reduced by etching two slots on the ground. The measured results show that the two PIFAs, respectively, achieve the impedance bandwidth of 5.14–6.03 GHz and 5.90–7.24 GHz, and the port isolation higher than 17.4 dB across 5.14–7.24 GHz frequency band. [ABSTRACT FROM AUTHOR]

In this letter, a broadband and low-profile frequency selective rasorber with an ultraminiaturized metal-graphene structure is proposed. The rasorber is composed of two cascaded layers separated by an air spacer, a top lossy layer and a bottom bandpass layer. By supplying four branches of multiple vias connected stubs across a circular graphene film in the lossy layer, extra inductance and capacitance effects are introduced while guaranteeing the impedance match with the free space at the low frequency range. As a result, a broad absorption bandwidth is ensured from 1.96 to 10.2 GHz with the thickness of only 0.076 λl at the lowest absorption frequency, and the passband is at 12.83 GHz with the insertion loss of 0.23 dB. Besides, a miniaturized unit is achieved with the period of 0.039 λl, and the oblique angle incidence response is up to 45° for TE and TM modes. To validate the design, a prototype is fabricated and measured, and the screen-printing process of graphene resistive film as omnidirectional resistance is adopted to further reduce the profile. The measured results agree well with the simulation. [ABSTRACT FROM AUTHOR]

In this letter, two compact, colocated, low-coupled, quad-polarized (QP) antennas are proposed based on two dual-mode radiation bodies to achieve compactness and high isolation. The first antenna obtains four polarizations by orthogonally placing two dual-mode loops; the second antenna includes a dual-mode loop and a miniaturized dual-polarized patch based on fractal structures inside the loop. To investigate the performance of QP multiple-input–multiple-output (MIMO) systems, channel parameters including correlation coefficients, degree of power balance, and channel capacities are analyzed based on the measured data. Results show that, high channel capacities can be achieved both in a realistic office room and a rich scattered reverberation chamber, which are very close to that of the 4 × 4 independently identically distributed (i.i.d.) Rayleigh channel. It is revealed that both correlation coefficient and degree of received power balance have strong influence on the performance of a MIMO system, which are related to the radiation properties of the antenna and the polarimetric characteristics of the propagation environment. [ABSTRACT FROM AUTHOR]

• The proposed work demonstrates a novel technique, high frequency transmission spectroscopy, for the characterization of bulk analyte in solution. • High frequency transmission spectroscopy is shown to be capable of measuring bulk electrolyte concentrations on the order of 10 µM, differentiate between monovalent and divalent anions/cations, and distinguish between ions with radii differences on the order of 40 pm. • High frequency transmission spectroscopy is shown to be capable of measuring concentration for nanoparticles of 3nm to microparticles on the order of 10 microns and differentiate between particles with radii differences on the order of 3 pm. This work illustrates a novel technique, high-frequency transmission spectroscopy (HFTS), for the characterization of analyte in aqueous solution. The application of this technique to material characterization is similar traditional impedance spectroscopy (IS) but differs primarily in that HFTS is a measure of transmitted potential through the material (voltage out versus voltage in) rather than its impedance (current out versus voltage in). The material properties explored by HFTS are not limited to effects occurring at the electrode/analyte interface which dominate IS measurements. Additionally, electric network analyzers (ENA), used for the characterization of frequency response, provide spectrum measurement capability over a much higher frequency range than typical impedance instrumentation. In this work, the capability of HFTS is demonstrated using three test cases: electrolyte solutions, carbon nanoparticles in solution, and sulfate latex microparticles in aqueous suspension. The experimental setup consists of a 3D printed liquid test cell, custom design patch antennae, and an off-the shelf ENA with a frequency range of 300 kHz to 500 MHz. The magnitude response of these analytes at various concentrations demonstrated a sensitivity of the measurement on the order of 10 µM. Furthermore, the system shows the ability to distinguish between monovalent and divalent ions and detect changes in radii on the order of 10 pm to 1 µm. Techniques demonstrated in this work have a wide range of potential applications including environmental monitoring, detection of polluting substances (e.g. PFAS) in water, and disease/infection screening. [ABSTRACT FROM AUTHOR]

Two-particle correlations are presented for K S 0 , ▪, and ▪ strange hadrons as a function of relative momentum in lead-lead collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The dataset corresponds to an integrated luminosity of 0.607 nb − 1 and was collected using the CMS detector at the CERN LHC. These correlations are sensitive to quantum statistics and to final-state interactions between the particles. The source size extracted from the K S 0 K S 0 correlations is found to decrease from 4.6 to 1.6 fm in going from central to peripheral collisions. Strong interaction scattering parameters (i.e., scattering length and effective range) are determined from the ▪ and ▪ (including their charge conjugates) correlations using the Lednický–Lyuboshitz model and are compared to theoretical and other experimental results. [ABSTRACT FROM AUTHOR]

Carbon-based materials, such as graphene, exhibit interesting physical properties and have been recently investigated in sensing applications. In this paper, a novel technique for glucose concentration correlation with the resonant frequency of a microwave resonator is performed. The resonator exploits the variation of the electrical properties of graphene at radio frequency (RF). The described approach is based on the variation in transmission coefficient resonating frequency of a microstrip ring resonator modified with a graphene film. The graphene film is doctor-bladed on the ring resonator and functionalised in order to detect glucose. When a drop with a given concentration is deposited on the graphene film, the resonance peak is shifted. The graphene film is modelled with a lumped element analysis. Several prototypes are realised on Rogers Kappa substrate and their transmission coefficient measured for different concentrations of glucose. Results show a good correlation between the frequency shift and the concentration applied on the film.

Recent advances in embedded antenna and sensor technologies for 5G communications have galvanized a response toward the investigation of their electromagnetic performance for urban contexts and civil engineering applications. This article quantitatively investigates the effects of material loading on an evolved antecedent hexagonal complementary split-ring resonator (CSRR)-loaded antenna design through simulation and experimentation. Optimization of the narrowband antenna system was first performed in a simulation environment to achieve resonance at 3.50 GHz, featuring an impedance bandwidth of 1.57% with maximum return loss and theoretical gain values of 20.0 dB and 1.80 dBi, respectively. As a proof-of-concept, a physical prototype is fabricated on a printed circuit board followed by a simulation-based parametric study involving antenna prototypes embedded into Ordinary Portland Cement pastes with varying weight percentages of iron(III) oxide inclusions. Simulation-derived and experimental results are mutually verified, achieving a systemic downward shift in resonant frequency and corresponding variations in impedance matching induced by changes in loading reactance. Finally, an inversion modeling procedure is employed using perturbation theory to extrapolate the relative permittivity of the dielectric loaded materials. Our proposed analysis contributes to optimizing concrete-embedded 5G antenna sensor designs and establishes a foundational framework for estimating unknown dielectric parameters of cementitious composites.

We propose a new residual model to analyze the uncertainty of scattering parameters (S-parameters) calibrated by an electronic calibration unit (ECU). Residual errors are usually estimated from the observed ripple after connecting a load or a short at the end of an airline. Therefore, this ripple method can only be used in a frequency range where the airline loss was not large. We, however, obtained the residual error from the uncertainty of the calibration kit using a simple numerical approach. As a result, we can determine the correlations between real/imaginary and magnitude/phase uncertainties. The proposed residual model showed the same results as a VNA error model. We also added a new error term to account for the effect of temperature-dependent drift of the ECU. In addition, we analytically derived the sensitivity coefficients for a 2-port DUT based on the proposed residual model. The proposed residual model will be helpful for the uncertainty analysis of S-parameters calibrated using the ECU.

In this paper the washability of a stitched transmission line is been studied. The aim is to determine the deterioration of the frequency dependence of the scattering parameters of the stitched transmission line after subjecting it to washing cycles using a domestic washing machine. The DC resistance of the stitched transmission line was measured before and after wash with results indicating an increase in the DC resistance from 16.9 Ω to 22.8 Ω after washing the stitched transmission line. The increase in DC resistance is due to the decrease in conductive path of the stitched transmission line as a result of the abrasion impacts in the washing machine leading to increased number of fissures and defects on the stitched transmission line. The propagation characteristics of the stitched transmission line were investigated using CST Microwave Studio Suite® and measurements on the stitched transmission line before and after wash was carried out using an Anritsu MS46524A 7GHz Network Analyser for a frequency range of 0.04 to 4 GHz, with results demonstrating that the stitched transmission line will make a good candidate for wearable applications.