Scattering Matrix Research Articles

Different Necking Models in Predicting the Measured Scattering Matrix of Soot Aggregates

Different Necking Models in Predicting the Measured Scattering Matrix of Soot Aggregates

Blocky Diagonalized Scattering Matrices in Chaotic Scattering with Direct Processes

Scattering matrices that can be diagonalized by a rotation through an angle θ in 2×2 blocks of independent scattering matrices of rank N, are considered. Assuming that the independent scattering matrices are chosen from one of the circular ensembles, or from the Poisson kernel, the 2N×2N scattering matrix may describe the scattering through chaotic cavities with reduced symmetry in the absence, or presence, of direct processes, respectively. To illustrate the effect of such symmetry, the statistical distribution of the dimensionless conductance through a ballistic chaotic cavity in the presence of direct processes is analyzed for N=1 using analytical calculations. We make a conjecture for N=2 in the absence of direct processes, which is verified by numerical random-matrix theory simulations, and the first two moments are calculated analytically for arbitrary N.

Design of a simple radio frequency circuit for implementing the open-ended coaxial probe method for permittivity measurement.

The development of electromagnetic (EM)-based therapeutic and diagnostic tools, as well as safety assessment of EM interactions with the human body, requires adequate measurement of the complex permittivity of different biological tissues. Such measurement techniques must be low-cost, readily available, and easy to implement. In this study, a simple circuit with basic radio frequency electronics was used to implement the open-ended coaxial probe method for permittivity measurement, as opposed to the widely used vector network analyzers. The non-ideal behavior of the circuit due to spurious reflections and ohmic losses was accounted for by a scattering matrix (SM) that relates the measured reflection coefficient to the true reflection coefficient at the probe tip. Parameters of SM were obtained using three calibration standards, and the circuit was used to measure the complex permittivity of a standard, tissue-equivalent, American Society of Testing Materials (ASTM) polymer gel. A more intuitive approach to circuit analysis is also introduced. For both methods, the dielectric constant and electrical conductivity of the gel were found to agree with the recommended uncertainties of the ASTM standard and validate the utility of the circuit at the test frequency.

Scan-Angle-Independent FEM Analysis of Infinite Arrays Based on Spherical Harmonic Lattice Sums and the Generalized Scattering Matrix of an Isolated Antenna

Infinite periodic arrays of antennas that can be individually described by means of spherical modes are analyzed starting from the generalized scattering matrix (GSM) of an isolated element. After computing the GSM of an isolated element with the finite-element method (FEM), a fast postprocessing can be carried out to calculate the response of the element in an infinite array environment by using addition theorems for spherical modes. For this purpose, an efficient computation of lattice sums of spherical harmonics is used. The main advantage of this method is that the antenna is analyzed only once whatever the array lattice or scan angle. In addition, fast frequency analysis can be performed since the starting point is the computation of the isolated antenna with the FEM, which is suitable for fast frequency sweep. The active reflection coefficient and the embedded radiation pattern of the infinite periodic array are calculated for several examples to show the capabilities of the proposed method.

Correlation between Scattering Matrix, Return Loss and Interface Reflection Loss in Nicolson Rose Wear Approximation

The phenomenon behind the absorption of electromagnetic waves by absorbingmaterials is resonance phenomenon. When there is a similarity between the value of theimpedance of electromagnetic waves in the air and the impedance of the material, theabsorption of energy by the material is maximized. The phenomenon is measured using anauxiliary instrument, namely the Vector Network Analyzer. This instrument is very effective forcalculating the absorption value of electromagnetic waves. However, the Vector NetworkAnalyzer instrument which is mostly available in Indonesian research institutions cannot directlydisplay the reflection loss of the electromagnetic wave absorbing material. An effective methodthat is effective for calculating the absorption in electromagnetic wave absorbing material isNicolson Rose Wear method. In this article, we design a computational tool based on NicolsonRose Wear approximation to calculate the reflection loss values from scattering matrix andcomparing it with return loss, which is often mistook as reflection loss.

Rigorous Analysis of a 26-GHz hybrid SIW coupler with Mode Matching Technique

In this paper, rigorous Mode-Matching Technique (MMT) with Generalized Scattering Matrix Method (GSMM) is used to analyze novel hybrid SIW coupler operating at 26 GHz for 5G applications. The introduced coupler has an equal-amplitude of about -3 dB besides 90-degree at its forward and coupled output ports with more than 4 GHz bandwidth. In addition to rigorous analysis, full-wave CST simulator is used to optimize coupler structure and the results from MMT and CST are compared and discussed. The coupler structure divided into two symmetrical cascaded parts with each part having multi-port bifurcated sections. Due to symmetrical structure, analyzing one half of the coupler with MMT has been sufficient for full analysis.

Research on Stability of Time-delay Force Feedback Teleoperation System Based on Scattering Matrix

Abstract The successful implementation of the robot teleoperation system has greatly improved the ability of remote robots. The force feedback technology is applied to the teleoperation system. On the one hand, the main operator manipulates the operator’s related movement information to the target robot; on the other hand, the main hand feeds back the force situation of the target robot in the remote control to the operator. From the robot under the control of the system can more accurately complete the task, with a higher work efficiency. Teleoperation system with force feedback function generally adopts bilateral control, the master and slave end of the system have a certain delay in the transmission process, it makes the stability of the system destroyed. This paper uses a two-port network to simulate the communications link of the teleoperation system as a lossless transmission line, solves the stability problem of teleoperation systems with force feedback in the presence of time delay effectively. Experimental simulation results show that this method can guarantee a higher stability of the system..

Application of Reciprocity to Calculating the Scattering Matrix of a Complex Muffler Without and With Nonuniform Meanflow

Application of Reciprocity to Calculating the Scattering Matrix of a Complex Muffler Without and With Nonuniform Meanflow

Analysis of SIW Crossover for 5G Beamforming Network Applications

A Mode-Matching Technique (MMT) with Generalized Scattering Matrix Method (GSMM) are deployed to design and analyze H-plane SIW crossover operating at 26 GHz for 5G beamforming networks applications. The introduced crossover has an 0 dB transmission over more than 4 GHz bandwidth. During the MMT formulation, the crossover structure is divided into two symmetrical cascaded parts with each part having multi-port bifurcated sections. Due to the symmetrical structure, analyzing one half of the coupler with MMT has been sufficient for full analysis. The obtained S-parameter results from MMT are compared with full-wave CST simulator results.

Bistatic Analysis Using the Real Representation Scattering Matrix Eigen-Classification

Exploring polarimetric diversity of Synthetic Aperture Radar (SAR) data is directly applicable to conventional monostatic cases. For this, the mostly used convention is the Backscatter Alignment. While establishing important advantages for the monostatic case (possibility to have equal values on the cross-polarimetric channels), it has been proven to introduce some difficulties for the bistatic case. This appears in relation to the so-called conjugate similarity operation, when (mathematically) asymmetric scattering matrices occur. In this paper, we propose the detailed algorithm which provides a solution to the conjugate similarity operation, in the case of general scattering matrices. The proposed algorithm is based on the real representation matrix transformation. Further, we investigate the characterization of canonical bistatic scatterers (three elementary targets). Raw bistatic polarimetric signals are obtained by using simulations with a computationally electromagnetic (EM) software, capable of complete EM analysis. The eigenvalue classification illustrates the potential of additional information brought using the proposed Real Representation Scattering Matrix (RRSM). The presence of complex eigenvalues is investigated in relation to the bistatic angle and one nonreciprocity parameter.

Teaching Scattering Matrix in Electrical Engineering—Misconceptions and Clarifications

This paper presents a new approach to introducing scattering parameters for dispelling doubts and misconceptions. Normalization of voltage and current is first introduced for the subsequent descriptions of normalized matrices. The analogy with lossless transmission lines is used to define voltage waves in terms of circuit voltages and currents. Scattering parameters are interpreted as reflection and transmission coefficients for real normalizing impedance. Power considerations are made to interpret scattering parameters as power ratios. The condition for the lossless circuit is derived, and it is shown that the definitions of the voltage waves satisfy maximum power transfer conditions for real input impedance. Reciprocity conditions are derived to show that the normalized, not the unnormalized scattering matrix, is symmetric. The application of losslessness and reciprocity in filter design is clarified. Next, it is shown why definitions of forward and reverse voltage have to be changed for complex normalizing impedances. The relationships of matrices for complex normalizing impedance are shown to reduce to those for real normalizing impedance. The procedure for changing normalizing impedance is given, and its application for amplifier design is briefly described. The difference between circuit symmetry and physical symmetry is pointed out. Finally, it is shown how odd and even mode analysis arises from a mathematical consideration of symmetrical two-port networks. A straightforward discussion of Wilkinson power divider is given to illustrate the application of these modes.

Influence of Nonhorizontal Orientation on Measurement of Insect Biological Parameters With Entomological Radar

Up till now, measurement of the biological parameters of insects traversing the beam of an entomological radar has been based on the assumption that the insects maintain a horizontal flight attitude. However, recent studies have revealed that some migrating insects fly with their bodies pitched upwards. This paper analyzes the influence of non-horizontal orientation (i.e. pitch and roll angles) on measurements of insect biological parameters with an entomological radar. The scattering matrices (SMs) of 15 insect specimens have been measured at different pitch and roll angles with a purpose-designed multi-aspect fully polarimetric laboratory rig. It is found that pitch angle has little influence on the discrimination of ‘parallel” and “perpendicular” insects, but it affects the measurement accuracy of orientation and estimation of mass and body length. The roll angle has little influence on the insect class discrimination, and the measurement of orientation and body length, and slightly affects the accuracy of the mass estimation. The influence of a general combination of pitch and roll angles is approximate the linear superposition of the influence of pitch angle and roll angle.

Mode Analysis of the Passive and Active Slab Waveguides Using Scattering Matrix

Mode Analysis of the Passive and Active Slab Waveguides Using Scattering Matrix

Current-Voltage Characterization of Multi-Port Graphene Based Geometric Diodes for High-Frequency Electromagnetic Harvesting

In this contribution, geometric diodes based on graphene patterned with spatial asymmetry have been studied, starting from tight-binding numerical approximation in a self-consistent framework, to verify their potential for electromagnetic (e. m.) harvesting. We report a detailed analysis of coherent charge transport and provide some figures of merit with respect to e. m. rectification, such as, for instance, the asymmetry of the dark current-voltage characteristics. The most important achievement of this work is given by the accurate analysis of the main key physical/geometric parameters that affect the nonlinear response of the diodes, for different configurations and geometries. Owing to the Scattering Matrix approach, introduced elsewhere for coherent transport calculation, it was possible to cascade asymmetric discontinuities and simulate large structures (more than 100K atoms) in a modular fashion. In this way, simulation at the atomistic level can be brought up to the device level to provide guidelines for design and fabrication, in view of practical applications related to clean-energy harvesting/rectification up to infrared and solar-light frequencies.

Universal Behavior of the Scattering Matrix Near Thresholds in Photonics.

Scattering thresholds and their associated spectral square root branch points are ubiquitous in photonics. In this Letter, we show that the scattering matrix has a simple universal behavior near scattering thresholds. We use unitarity, reciprocity, and time-reversal symmetry to construct a two-parameter model for a two-port scattering matrix near a threshold. We demonstrate this universal behavior in three different optical systems, namely, a photonic crystal slab, a planar dielectric interface, and a junction between metallic waveguides of different widths.

Ultrasonic Defect Characterization Using the Scattering Matrix: A Performance Comparison Study of Bayesian Inversion and Machine Learning Schemas.

Accurate defect characterization is desirable in the ultrasonic nondestructive evaluation as it can provide quantitative information about the defect type and geometry. For defect characterization using ultrasonic arrays, high-resolution images can provide the size and type information if a defect is relatively large. However, the performance of image-based characterization becomes poor for small defects that are comparable to the wavelength. An alternative approach is to extract the far-field scattering coefficient matrix from the array data and use it for characterization. Defect characterization can be performed based on a scattering matrix database that consists of the scattering matrices of idealized defects with varying parameters. In this article, the problem of characterizing small surface-breaking notches is studied using two different approaches. The first approach is based on the introduction of a general coherent noise model, and it performs characterization within the Bayesian framework. The second approach relies on a supervised machine learning (ML) schema based on a scattering matrix database, which is used as the training set to fit the ML model exploited for the characterization task. It is shown that convolutional neural networks (CNNs) can achieve the best characterization accuracy among the considered ML approaches, and they give similar characterization uncertainty to that of the Bayesian approach if a notch is favorably oriented. The performance of both approaches varied for unfavorably oriented notches, and the ML approach tends to give results with higher variance and lower biases.

Detection of band edge frequencies in symmetric/asymmetric dielectric loaded helix slow‐wave structures

AbstractThe significant contribution of this paper is to present a comprehensive analysis and design of π‐point and band edge frequencies of reported helix SWSs including not only a microwave but also millimeter‐wave operation frequencies considering the methods in available literature which are the Coupled Mode Analysis (CMA), the Exact Floquet Approach (EFA), and the Auxiliary Functions of Generalized Scattering Matrix (AFGSM) as a comparative study. A different approach called as effective rod model is applied to circular/T‐shaped dielectric support rod helix SWSs in order to obtain ladder circuit representation of one turn of related helix SWSs for the first time. Scattering matrices of equivalent circuit representation of interested helix SWSs are obtained by using microstrip line model of helix SWS which slits helical tape at the effective helix radius along the direction normal to the helix winding direction and flattens it out for the EFA, the AFGSM, and the CMA methods. Additionally, comparisons are given for investigated methods together with the results of Computer Simulation Technology (CST) design environment, and good agreement has been observed among numerical results of different helix SWSs in a broad frequency range.

Alternative Formulation of Antenna Arrays for DF Systems Considering Active-Element Patterns and Scattering Matrices.

Direction finding (DF) systems are used to determine the direction-of-arrival (DoA) of electromagnetic waves, thus allowing for the tracking of RF sources. In this paper, we present an alternative formulation of antenna arrays for modeling DF systems. To improve the accuracy of the data provided by the DF systems, the effects of mutual coupling in the array, polarization of the received waves, and impedance mismatches in the RF front-end receiver are all taken into account in the steering vectors of the DoA algorithms. A closed-form expression, which uses scattering parameter data and active-element patterns, is derived to compute the receiver output voltages. Special attention is given to the analysis of wave polarization relative to the DF system orientation. Applying the formulation introduced here, a complete characterization of the received waves is accomplished without the need for system calibration techniques. The validation of the proposed model is carried out by measurements of a 2.2 GHz DF system running a MUSIC algorithm. Tests are performed with a linear array of printed monopoles and with a planar microstrip antenna array having polarization diversity. The experimental results show DoA estimation errors below 6° and correct classification of the polarization of incoming waves, confirming the good performance of the developed formulation.

An Overview of the Compton Scattering Calculation

The Compton scattering process plays significant roles in atomic and molecular physics, condensed matter physics, nuclear physics and material science. It could provide useful information on the electromagnetic interaction between light and matter. Several aspects of many-body physics, such us electronic structures, electron momentum distributions, many-body interactions of bound electrons, etc., can be revealed by Compton scattering experiments. In this work, we give a review of ab initio calculation of Compton scattering process. Several approaches, including the free electron approximation (FEA), impulse approximation (IA), incoherent scattering function/incoherent scattering factor (ISF) and scattering matrix (SM) are focused on in this work. The main features and available ranges for these approaches are discussed. Furthermore, we also briefly introduce the databases and applications for Compton scattering.

Application of the Scattering Matrix Method for Calculation of Impurity States in Semiconductor Structures

Application of the Scattering Matrix Method for Calculation of Impurity States in Semiconductor Structures