Reactive Impedance Research Articles

Kirchhoff and Ohm in action: solving electric currents in continuous extended media

In this paper we show a simple and versatile computational simulation method for determining electric currents and electric potential in 2D and 3D media with arbitrary distribution of resistivity. One of the highlights of the proposed method is that the simulation space containing the distribution of resistivity and the points of external applied voltage are introduced by means of digital images or bitmaps, which easily allows simulating any phenomena involving distributions of resistivity. The simulation is based on the Kirchhoff’s laws of electric currents and it is solved by means of an iterative procedure. The method is also generalised to account for media with distributions of reactive impedance. At the end of this work, we show an example of application of the simulation, consisting in reproducing the response obtained with the geophysical method of electric resistivity tomography in presence of soil cracks. This paper is aimed at undergraduate or graduated students interested in computational physics and electricity and also researchers involved in the area of continuous electric media, which could find a simple and powerful tool for investigation.

Dielectric relaxation behavior and impedance studies of Cu2+ ion doped Mg – Zn spinel nanoferrites

Cu2+ substituted Mg – Zn nanoferrites is synthesized by low temperature fired sol gel auto combustion method. The spinel nature of nanoferrites was confirmed by lab x-ray technique. Williamson – Hall (W-H) analysis estimate the average crystallite size (22.25–29.19 ± 3 nm) and micro strain induced Mg0.5Zn0.5-xCuxFe2O4 (0.0 ≤ x ≤ 0.5). Raman scattering measurements confirm presence of four active phonon modes. Red shift is observed with enhanced Cu concentration. Dielectric parameters exhibit a non – monotonous dispersion with Cu concentration and interpreted with the support of hopping mechanism and Maxwell-Wagner type of interfacial polarization. The ac conductivity of nanoferrites increases with raising the frequency. Complex electrical modulus reveals a non – Debye type of dielectric relaxation present in nanoferrites. Reactive impedance (Z″) detected an anomalous behavior and is related with resonance effect. Complex impedance demonstrates one semicircle corresponding to the intergrain (grain boundary) resistance and also explains conducting nature of nanoferrites. For x = 0.2, a large semicircle is observed revealing the ohmic nature (minimum potential drop at electrode surface). Dielectric properties were improved for nanoferrites with x = 0.2 and is due to high dielectric constant, conductivity and minimum loss value (∼0.009) at 1 MHz.

Wideband THz antenna using graphene based tunable circular reactive impedance substrate

This letter presents a graphene–based tunable circular reactive impedance substrate (G–CRIS) operating at THz frequency. The proposed RIS is composed of sectoral graphene patch elements, arranged in two concentric rings and printed over silicon dioxide layer which is backed by a thin gold layer. The reactive behavior of the CRIS is made tunable by applying different chemical potential on graphene patches. This tunable CRIS is employed further to improve the operational bandwidth of a THz antenna. The CRIS loaded antenna exhibits miniaturized resonance at the lower band and wideband characteristics at the upper band. Both gain and efficiency of the antenna have been studied throughout the operating band. It is found that at THz frequency this graphene–based RIS is more suitable than metallic RIS for controlling the operational bandwidth.

Direction-of-Arrival Estimation Enhancement for Closely Spaced Electrically Small Antenna Array

In this paper, compact direction finding systems using a scatterer of a high dielectric constant in between adjacent closely spaced electrically small antennas are examined. By adding a high-permittivity scatterer, the directional sensitivity can be enhanced. However, due to limited physical dimension, an electrically small antenna has highly reactive impedance. To enhance the received power level, a matching network is included. The highest directional sensitivity satisfying a given power constraint is compared for with and without scatterer cases. In addition, widely used matching approaches such as multiport-conjugate matching (MCM), self-conjugate matching (SCM), and eigenmode decoupling matching are investigated to increase the received power. The impact of these matching networks on the directional sensitivity is studied. The power and the directional-sensitivity bandwidth after matching are also analyzed. Finally, the two-monopole and a high-permittivity scatterer system with SCM and MCM circuits is fabricated and tested.

A Zero Index Based Meta-Lens Loaded Wideband Directive Antenna Combined With Reactive Impedance Surface

In this paper, an aperture efficient wideband high-gain patch antenna is designed using a novel multilayer-based metamaterial structure combined with a reactive impedance surface (RIS)-backed patch antenna. The metamaterial unit cell is a two-layer structure which is stacked one after other to form the overall unit cell. The microscopic behavior of the proposed unit cell has been investigated. This unit cell gives low refractive index over a wide bandwidth with a negligible loss. An RIS-backed patch antenna has been designed in the required frequency band to feed the multilayer zero-index metamaterial medium. The introduction of this surface is to provide unidirectional radiation over a wideband in the zero refractive index region. The proposed antenna gives a 14% fractional bandwidth over the $C$ - and $X$ -bands. The proposed antenna enhances the peak gain of the conventional patch antenna by an amount of 8.5 dB at 8 GHz. Finally, the antenna has been fabricated and its performance is verified experimentally.

Technique of increasing the impedance measuring transducers accuracy at inharmoniousness signals

Introduction. Nowadays, one of the most relevant classes of sensor electronics for the Internet of Things is based on the methods of impedance spectroscopy. In general, the informative signals of impedance spectroscopy, namely, an active component or resistance which forms the real part and a reactive component or reactance which forms the imaginary part of complex impedance of the investigated two-terminal network, are formed by specialized analog front-end or measuring transducers. The defining requirements for measuring converters of sensor devices of the Internet Things are their versatility, minimal power consumption, the ability to work at low supply voltages, stability of operation with changing external factors and so on. In this paper, the problem of improving the accuracy of electrical impedance measuring transducers is considered, taking into account the non-harmonic of the driving signals. SPICE model and research technique. The implementation of impedance spectroscopy assumes a transition from frequency plots to plots on the complex plane, called as Nyquist plots. In a number of modern versions of circuit simulation programs the method of impedance analysis is already provided with the use of mathematical functions of Real (Re) and Imagine (Im) components of the signal. Using these functions, it is possible to calculate the corresponding values of the active (Re Z) and the reactive (Im Z) impedance of the object under investigation. As a result of his usage a Nyquist plot is plotted. However, this approach is not universal, and in particular, imposes significant restrictions taking into account the parameters of real signals, namely, their amplitude, shape, non-harmonics, etc. The results obtained in this paper are based on the new SPICE (Simulation Program with Integrated Circuit Emphasis) model studding methodology, which compares small signal Alternative Current Analysis with large signal Transient Analysis. During the Alternative Current Analysis, Nyquist impedance plot are obtained in the idealized case, and during the Transient Analysis the active Re Z value and reactive Im Z impedance components are calculated for the actual parameters of the measuring transducers and the form of the activating signals. The implementation of the above mentioned methodology involves the use of synchronous quadrature detection of the output signals of the measuring circuit. Analysis and correction of results. In accordance with the task of increasing the impedance measuring transducers accuracy at inharmoniousness signals we consider the method of calculating the coefficients KRE and KIM, allowing correcting the measurement results of the active Re Z and the reactive Im Z impedance components. A few analysis and correction results are presented. The obtained regularities can be widely used in correcting the results of impedance spectroscopy upon activation by pulse signals for the vast majority of research options. Conclusion. A new approach is proposed, according to which three arrays of informative signals of active Re Z and reactive Im Z impedance are formed and compared. The first M(AC) array is obtained using small signal Alternative Current Analysis, which corresponds to an idealized version of the measurement transformation and is subsequently used as a reference. The next two arrays M(H1) and M(HN) are obtained by the method of large signal Transient Analysis using the results of integrating the quadrature detector output voltages of the impedance transducer. The array M(H1) is formed when the input source triggers a harmonic oscillation (the first H1 harmonic), and the M(HN) array when activated by a functionally controlled source synthesizes a non-harmonic signal in the form of harmonics HN. The increase in the accuracy of the measurement conversion is provided by coefficients $K_{RE}$ and $K_{IM}$, which allow the correction of the measurement results of the active and reactive components of the impedance. A method for calculating such coefficients and examples of their use are presented.

Perfect reflection control for impenetrable surfaces using surface waves of orthogonal polarization

For impenetrable electromagnetic surfaces, a metasurface design approach for perfect control of the reflection phenomena using gradient anisotropic tensor surface impedance is presented. It utilizes a set of orthogonally polarized auxiliary surface waves to create pointwise reactive impedance characteristics by channeling power along the tangential direction of the surface in the near zone in a carefully designed manner. The propagating incident and reflected fields do not interfere with the surface waves due to the polarization orthogonality. Design examples of an anomalous reflector and a power splitter for an incident plane wave are presented and numerically verified. Realization possibilities using an array of rotated metallic resonators on a thin grounded dielectric substrate are discussed.

Miniaturization of a patch antenna using circular reactive impedance substrate

In this article, to construct a reactive impedance substrate, unit ring is designed and proposed with radial and concentric mode analysis. A cylindrical substrate backed with a PEC plane and circular metallic elements on the top is used for achieving reactive surface impedance behavior. In this aspect, three unit rings structure with different ring elements are designed and simulated to realize the reflection phase characteristics. Afterwards, a probe-fed circular patch antenna is miniaturized by stacking the three-ring circular reactive impedance surface. The fundamental resonance frequency of the proposed antenna is reduced by about 30% with an improvement in impedance bandwidth by 121.6%. An improved front-to-back ratio as well as an acceptable co-pol and cross-pol isolation is exhibited in both E-plane and H-plane at the resonance frequency. In addition of miniaturization, dual band behavior has also been observed in the proposed design. Both resonance phenomena have been explained by circuit model representation and surface current distribution analysis. Improved radiation efficiency at 81.5% has been measured for the proposed antenna configuration.

Over Second Octave Power Amplifier Design Based on Resistive–Resistive Series of Continuous Class-F/F−1 Modes

This letter presents a novel methodology for resistive–resistive series of continuous class-F/ $\text{F}^{{\mathbf {-1}}}$ modes (Res.–Res. SCF/ $\text{F}^{{\mathbf {-1}}}$ Ms) power amplifier (PA) design. The bandwidth is expanded by designing the lower band with resistive second- and third-harmonic impedances and the upper band with resistive second-harmonic impedance and reactive third-harmonic impedance using a waveform engineering method. Mathematical derivation of the methodology is described in detail. The proposed design is experimentally verified using a Res.–Res. SCF/ $\text{F}^{{\mathbf {-1}}}$ Ms PA operating across 0.4–2.3 GHz with 62.3%–80.5% drain efficiency and 39–42 dBm output power.

Meander line‐based low profile RIS with defected ground and its use in patch antenna miniaturization for wireless applications

ABSTRACTA reactive impedance surface (RIS) comprising of 4 × 4 array of grounded unit cells having meander line structure is designed. A detailed impedance analysis of the RIS is presented and validated with simulation results. A triangular patch antenna with metallic ground plane is designed to resonate at 3.78 GHz. The metallic ground is substituted by the RIS which results in shifting of resonant frequency from 3.78 GHz to 2.90 GHz thus exhibiting 23.28% miniaturization. The metallic ground of RIS is made defected by etching a rectangular slotted loop which leads to 50.8% miniaturization as the resonant frequency of the structure shifts to 1.86 GHz which resembles to GSM communication frequency. A tuning parameter has been identified in the slotted loop to control the resonant frequency of the structure. Satisfactory gain, efficiency and stable radiation pattern with low cross polarization level in both E and H planes qualify the proposed structure as a promising candidate for practical wireless applications. A comparison of the proposed structure with previous works in literature is provided to demonstrate the superiority of the proposed technique in terms of the profile of RIS and its miniaturization capability. Experimental verification of the proposed structure is provided. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:732–738, 2017

Design and analysis of annular ring-based RIS and its use in dual-band patch antenna miniaturization for wireless applications

This paper proposes the design of a Reactive Impedance Surface (RIS) which comprises a 5 × 5 array of grounded unit cells. The unit cells have annular ring structures on their top surfaces. A detailed analysis of the unit cell leading to its impedance characteristic is presented and validated with simulated results. The RIS exhibits inductive impedance below 4.92 GHz. Next, the RIS is used as the ground of a dual-band patch antenna instead of a metallic ground for the purpose of miniaturization. As a result, the lower resonant frequency of the antenna is lowered from 3.36 to 2.4 GHz exhibiting 28.6% miniaturization. The higher resonant frequency is decreased from 4.77 to 3.43 GHz exhibiting 28.1% miniaturization. The theory of antenna miniaturization using RIS is also discussed. The lower and higher resonant frequencies of the miniaturized antenna correspond to the WiFi and WiMAX frequencies, respectively. The gain and efficiency at these two frequencies are significant and radiation patterns are stable with low cross- polarization level. Hence, the proposed structure can be used for practical wireless applications.

Compact circularly polarized conical‐beam antenna based on the reactive impedance substrate

ABSTRACTA compact circularly polarized (CP) conical‐beam antenna based on the reactive impedance substrate (RIS) is proposed in this work. This single‐fed antenna utilizes a small circular patch and six curved branches as primary radiators. For the miniaturization purpose, the RIS structure is used, and an overall volume of only 0.66λ × 0.66λ × 0.066λ with respect to 5 GHz is achieved. For experimental demonstration, the proposed antenna is fabricated and tested. Acceptable agreements are obtained between the measured and simulated results. The antenna peak gain at the center frequency is 3.3 dBic and occurs at θ = 48°. Moreover, good omnidirectional CP feature is obtained. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:240–243, 2017

Analogs and characteristics of compensated asynchronous machines with different numbers of phases

The disadvantages of three-phase asynchronous motors with short-circuited rotors, which are widely used in practice, are discussed. It is determined that the most significant disadvantage is consumption of two types of electric energy from a network: active energy for conversion into mechanical energy accompanied by inevitable heat losses and reactive energy that is not converted into other types of energy, but is expended on generation of the magnetic field required for electromechanical conversion of energy in an electrical machine. It is suggested to use internal capacitive compensation of reactive power to improve the technical and economic indices of asynchronous machines of both motors and generators. In addition, each phase winding of the asynchronous machine stator is divided into two parts equal in number of turns spatially shifted between each other in the core slots by an angle of 30°. These parts are connected according to the scheme of the rotary autotransformer to the electrical capacity at its output. The change of the spatial position of the stator windings leads to a change in time of the action of the phase angles of their electromotive force and, therefore, of currents and voltages without changing the introduced reactive impedances. Thus, the spatial coordinate of the electrical value is converted into the time coordinate in the electromagnetic circuit with a rotating magnetic field. The combination of this property of the stator windings in accordance with the rotary autotransformer with the action of the electrical capacity at its output creates the effect of internal capacitive compensation of reactive power in an asynchronous machine. The ability to use internal capacitive compensation of reactive power in single-phase asynchronous machines is considered. A method of calculation of the characteristics of compensated asynchronous machines taking into account the change of the magnetizing contour resistance is presented. The advantages of compensated asynchronous motors and compensated asynchronous generators are determined. Recommendations as to their effective practical use are given.

The use and mis-use of reactive systems in the design of performance halls

While the “surface of infinite impedance” or “totally absorptive material” makes our acoustic theories understandable and our analytical calculation methods useful, more often than not such conditions are not met in built performance facilities. Since the materiality of a performance hall strongly influences the quality of sound within a space, the physical reality of the reactive impedance of building elements must be managed to achieve quality sound. This paper discusses the practical application of various room acoustic design options, including wall and ceiling material choices, and offers comment on how various reactive systems within performance halls can detract from a room and/or reintroduce sound energy into a space. Discussion will occur regarding how such conditions can be either favorable or detrimental to the aural environment. Examples will be offered which suggest a reactive room surface can offer favorable room acoustic results for impulsive sound events, and unfavorable results with sustained sound events. Observations and subsequent testing suggest that the ability to discern the impact of reactive systems within a hall depends upon the test methods implemented during acoustic measurement sessions.

Reactive impedance surface based multisystem satellite navigation antenna

ABSTRACTA reactive impedance surface (RIS) based novel antenna that covers operating bands of multiple global navigation satellite systems (GNSSs) is presented. By using the metamaterial covering layer, that is, the RIS, the antenna achieves wideband performance in terms of both reflection coefficient and axial ratio (AR). For reflection coefficient lower than −10 dB, the operating band is 1.26–1.73 GHz. The AR bandwidth of the antenna that is lower than 3 dB is 1.33 GHz–1.71 GHz, enabling it compatible with several GNSSs including GPS, GLONASS, Beidou, and Galileo. In addition, the antenna radiates an axial beam with a peak gain of 6.0 dBic in the form of the right‐handed circular polarization. The antenna has a favorable peak radiation efficiency of 93.3% in the operating band while keeping a compact size of 0.38 λ0 × 0.38 λ0 × 0.097 λ0 at 1.33 GHz.© 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2764–2769, 2016

Analysis of Miniature Metamaterial and Magnetodielectric Arbitrary-Shaped Patch Antennas Using Characteristic Modes: Evaluation of the <inline-formula> <tex-math notation="LaTeX">$Q$ </tex-math> </inline-formula> Factor

Evaluating the $Q$ factor of antennas using metamaterial substrates is a challenge and requires new analysis techniques. This challenge is even more important for arbitrary-shaped antennas. In this paper, we address the problem of analysis and evaluation of metamaterial-based antennas through the use of characteristic modes. We propose a new expression for the total $Q$ factor, which is independent of the excitation and based on the eigenvalues of the structure. The proposed expression is used to compute the $Q$ factor of an arbitrary-shaped resonant antenna and shows excellent agreement with other expressions in the literature such as the ones proposed by Yaghjian, Best, and Gustafsson. The approach is then used to analyze small patch antennas over metamaterial and magnetodielectric substrates. It is shown using the defined $Q$ factor expression that a magnetic substrate offers a significant bandwidth enlargement for the first active modes, and a dielectric substrate presents the opposite effect. This agrees with other works based on analytical approaches. Furthermore, we demonstrate that a reactive impedance metamaterial substrate presents identical modal significances that are identical to a conventional magnetodielectric substrate when associated with a patch antenna. This analysis is suitable for structures presenting noncanonical geometries and arbitrary shapes such as metamaterial inclusions.

Simulation of an interturn fault in a stator winding of a synchronous condenser

A method of simulation of interturn faults in a stator winding in steady state operating conditions of synchronous condenser is proposed. The method is based on a mathematical model with the equations of the mesh current method for phase-to-phase voltages. Expressions for active and reactive impedances of the windings are presented. The initial data for calculation of resistance and reactance of stator and rotor windings are obtained experimentally. Experiments proved that the proposed method simulates interturn faults in a stator winding with a maximum error of 5–10%.

H-RIS inspired Koch fractal antenna for S- and C-band SAR applications

A compact dual band H-shape reactive impedance surface (H-RIS) metamaterial loaded Koch fractal antenna is presented in this paper. The array of H-shape unit cell resonators is used to form reactive impedance surface. Resonance occurred at 3.4 and 5.35 GHz frequency bands. These frequency bands are feasible to use at C- and S-bands synthetic aperture radar (SAR) applications. The geometry of proposed antenna is designed with low-cost substrate FR-4. Radiation patterns are measured and compared with the simulation results for testing the overall performance of the newly designed antenna. The measured results are well matched with simulation one. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1311–1314, 2016

Control of Active and Reactive Power Ripple to Mitigate Unbalanced Grid Voltages

Managing power delivery from distributed generation systems is challenging when the grid voltages are unbalanced, since the negative sequence voltage causes power oscillations at twice the fundamental grid frequency. Current regulation using sequence components can be used to manage these real and reactive power oscillations, and thus help mitigate the unbalanced network voltages. This paper presents a consolidated control scheme using double sequence frame current regulators that can readily adjust between eliminating real or reactive power oscillations created by unbalanced grid voltages, or alternatively can simply balance the three-phase currents. The mitigation influence of these alternative control strategies on unbalanced grid voltages is then experimentally examined for a distribution feeder with a resistive and/or reactive series impedance.

Finite Volume Time Domain Room Acoustics Simulation under General Impedance Boundary Conditions

In room acoustics simulation and virtualization applications, accurate wall termination is a perceptually crucial feature. It is particularly important in the setting of wave-based modeling of 3D spaces, using methods such as the finite difference time domain method or finite volume time domain method. In this paper, general locally reactive impedance boundary conditions are incorporated into a 3D finite volume time domain formulation, which may be specialized to the various types of finite difference time domain method under fitted boundary termination. Energy methods are used to determine stability conditions for general room geometries, under a large family of nontrivial wall impedances, for finite volume methods over unstructured grids. Simulation results are presented, highlighting in particular the need for unstructured or fitted cells at the room boundary in the case of the accurate simulation of frequency-dependent room mode decay times.