Distributed-element Circuit Research Articles

Tomonaga–Luttinger-liquid nature of edge excitations in integer quantum Hall edge channels

Abstract In interacting one-dimensional (1D) systems, the quasi-particle picture in Fermi-liquid theory cannot successfully describe low-energy physics. Instead, electron dynamics in one dimension can be described as collective excitations, i.e., charge- and/or spin-density waves, which are elementary excitations in a Tomonaga-Luttinger (TL) liquid. Integer quantum Hall (QH) edge channels, which are chiral 1D electron states formed along the periphery of integer QH systems, provide a unique opportunity for studying TL-liquid physics. When edge channels lie parallel to each other, inter-channel interactions induce significant TL-liquid behaviors in coupled plasmons. One can prepare an arbitrary number of co- and/or counter-propagating channels of spin-up or -down electrons to form such a multiple edge-channel system. The plasmon dynamics can be experimentally investigated by using various functional devices such as charge injectors, detectors, and spin filters to select spin and bidirectional-momentum degrees of freedom. This article reviews electron dynamics in such QH TL liquids. We first introduce the chiral distributed-element circuit model for describing interactions in single and multiple integer-edge-channel systems. This simple model captures the TL-liquid nature of the 1D plasmon transport. We then review experimental studies on TL-liquid behaviors. These experiments show that plasmon velocity is significantly enhanced by the intra-channel interaction. In addition, they show that co-propagating channels with spin degrees of freedom exhibit TL-liquid behavior known as spin-charge separation, in which spin and charge excitations behave differently. This is demonstrated with a novel time- and spin-resolved charge detection technique. They also reveal that charge fractionalization occurs at the boundaries of counter-propagating channels with bidirectional-momentum degrees of freedom. A charge excitation even as small as an electron charge is fractionalized into smaller charges to form coupled plasmons in the interacting region. These experiments highlight the intriguing quantum many-body nature of QH TL liquids.

Visualization of the carrier transport dynamics in layered Organic Light Emitting Diodes by Modulus spectroscopy

Abstract Carrier transport behavior in organic light emitting diode (OLED) is visualized by Modulus spectroscopy using typical layered devices ITO/α-NPD/Alq3/LiF/Al. Two techniques of Modulus analysis, Dynamic Modulus Plot (DMP) and Distributed Circuit Element (DCE) analysis are presented. The hole distribution in NPD layer is visualized by DCE model. The DMP and the DCE model show that the hole and electron transport in NPD/Alq3 devices up to 10 mA/cm2 obey not to a space charge limited current but an Ohmic conduction. It is well known that holes accumulate in NPD even below the turn-on voltage of DC current. This hole accumulation depends on both of NPD and Alq3 layer thicknesses. The voltage dependence is scaled by the Alq3 thickness, whereas the carrier density dependence by the NPD thickness. We propose a model that the accumulated holes are supplied by the thermal activation of the finite number of shallow trap sites localizing at ITO/NPD interface.

Equivalent Voltage and Current Waves for TM SPP in Graphene Sheets

We present a theoretical model to describe the propagation of a transverse magnetic surface plasmon polariton in graphene based on equivalent voltage and charge current waves, which includes the spatial dispersion effect. Electrons and holes in graphene are governed by the Boltzmann equation in the particle conserving relaxation time approximation. First, we deduce expressions for the non-equilibrium distributions when there are charge oscillations in graphene as a response to the electromagnetic field applied to it. These distribution functions are used in the Boltzmann equations to derive other equations for the following four local macroscopic averages: the oscillating electron and hole densities, and the electron and hole current densities. Then, for a specific structure, we solve the wave equations for the electric and vector magnetic potentials to obtain the relations between the charge oscillations and the potentials. So, we reach a homogeneous system of four coupled equations relating the amplitudes of the voltage and the current waves. The non-trivial solutions of the system allow us to compute the dispersion and loss curves for such waves. As it is already known, for a given frequency, we can see that the higher the Fermi level is, the lesser the spatial-dispersion effect is. Following the analysis, a distributed-element circuit for the equivalent transmission line in which would propagate the waves, is developed. Finally, we analyze the dependence of these circuit elements and the impedance on both the frequency and Fermi level.

Magnetless Microwave Circulators Based on Spatiotemporally Modulated Rings of Coupled Resonators

Nonreciprocal components are ubiquitous in electronic and optical systems. To date, the use of magneto-optical materials has been the prevailing method to achieve nonreciprocity. However, magnetic-based devices are accompanied by several drawbacks, such as the requirement of bulky biasing devices and their incompatibility with semiconductor technology, which make their integration challenging. Recently, strong magnetless nonreciprocity was demonstrated in spatiotemporally modulated coupled-resonator networks as a result of an effective spin imparted to the structure by an RF signal. These structures can be easily integrated, and they potentially exhibit good power and noise performance, as any parametric device. Here, we develop an analytical theory for such devices, which allows determining the conditions for designing them with optimum characteristics, and present two designs based on lumped- and distributed-element circuits for applications at the very high-frequency and wireless-communications bands, respectively. The circulators exhibit large isolation and low insertion loss within reasonable modulation requirements. Furthermore, they can be realized with a modulation frequency substantially lower than the input frequency, significantly simplifying the design. Measurements for the lumped-element design are provided and show good agreement with theory and full-wave simulations. The nonlinear characteristics of the presented designs are also studied, and possible ways to reduce nonlinear distortion by increasing the static bias of the varactors or using advanced varactor topologies are explored.

Performance evaluation of parallel electric field tunnel field-effect transistor by a distributed-element circuit model

The performance of parallel electric field tunnel field-effect transistors (TFETs), in which band-to-band tunneling (BTBT) was initiated in-line to the gate electric field was evaluated. The TFET was fabricated by inserting an epitaxially-grown parallel-plate tunnel capacitor between heavily doped source wells and gate insulators. Analysis using a distributed-element circuit model indicated there should be a limit of the drain current caused by the self-voltage-drop effect in the ultrathin channel layer.

Effects of drought on electrical impedance spectroscopy parameters in stems of Pinus bungeana Zucc. seedlings

The effects of drought during preplanting (three treatments: soil relative water content (RWC) 75%–80%, 55%–60%, 35%–40%; B1, 2, and 3, respectively) and postplanting (four treatments: RWC 75%–80%, 55%–60%, 35%–40%, 15%–20%; A1, 2, 3, and 4, respectively) on electrical impedance spectroscopy (EIS) parameters in the stems of Pinus bungeana Zucc. seedlings were investigated by using 4-year-old container seedlings. Stem impedance spectra were modeled by a distributed circuit element model (2-DCE), which showed the extracellular and intracellular resistance (re and ri), relaxation time (τ1 and τ2), and distribution coefficient (ψ1 and ψ2) of relaxation time. After preplanting B3 drought treatment, re and ri increased significantly with the increase of soluble sugar of the stem, measured by enthronlsulphuric acid method. After four weeks postplanting A4 drought treatment, relative conductivity, and soluble sugar of stem increased significantly, and re of stem decreased significantly and continually, indicating that the cell membrane of stem cells was disrupted by severe drought. After five weeks drought treatment, τ1 of stem under A4 treatment decreased significantly, and ψ2 of stem under A2, A3, and A4 treatments was higher than that of A1 treatment. Briefly, drought made re, ri, τ1, and ψ2 of stem change regularly, but re was found to be the most informative and useful parameter measured if used as a single index to assess the drought resistance of P. bungeana Zucc. seedlings.

Parasitic Compensation Design Technique for a C-Band GaN HEMT Class-F Amplifier

A class-F/inverse class-F load circuit design method that includes parasitic elements such as drain-source capacitance and bonding wire inductance has been developed. For the class-F load circuit design, a reactance function which has zeros at even harmonic frequencies and poles at odd harmonic frequencies is expanded to an -ladder circuit including parasitic elements through the use of the second Cauer canonical form. For the inverse class-F load circuit design, the zero points and the poles are exchanged. One stage of the -ladder circuit can be approximately replaced to a distributed circuit element for higher frequency operation. The proposed method allows parasitic compensation up to an arbitrary harmonic order by adding zeros and poles. Additionally, if distributed circuit elements are used, the method also compensates frequency dispersive characteristics of microstrip lines. According to the proposed method, a class-F amplifier using an AlGaN-GaN HEMT has been fabricated at 5.8 GHz. The fabricated class-F amplifier delivered high efficiency characteristics, with a maximum drain efficiency of 79.9%, a maximum power-added efficiency (PAE) of 71.4%, and an output power of up to 33.4 dBm at 5.86 GHz.

Extraction of Subterahertz Transmission-line Parameters of Coplanar Waveguides

Building on our previous work that compared computed propagation charac- teristics of picosecond pulses on coplanar waveguides (CPW's) with experiments, we extract transmission-line parameters, including resistance, inductance, conductance, and capacitance, from S-parameters up to subterahertz frequencies. The distributed-element circuit model is an- alyzed for applications in CPW-based circuit design. DOI: 10.2529/PIERS060912144405

Effects of elevated concentrations of ozone and carbon dioxide on the electrical impedance of leaves of silver birch (Betula pendula) clones.

Effects of elevated concentrations of tropospheric ozone ([O3]) and carbon dioxide ([CO2]) on leaves of two silver birch (Betula pendula Roth) clones were monitored for three growing seasons (1998, 1999, 2000) by means of electrical impedance spectroscopy (EIS). The field trial with open-top chambers (OTCs) was conducted on two clones (Clone 4 and Clone 80) with five treatments and four independent replicates. Treatments were: (1) outside control, (2) chamber control, (3) 2x ambient [O3], (4) 2x ambient [CO2] and (5) 2x ambient [CO2] + 2x ambient [O3]. Fumigations started in 1999 and continued in 2000. Measurements were made in 1998 before the fumigations and thereafter EIS was carried out four times in each season. The impedance spectra of about 10 leaves from each tree at each time were measured at 42 frequencies between 80 and 1 MHz. Leaf spectra were modeled by a distributed circuit element model (DCE) (one DCE in series with a resistor), which yields the extracellular and intracellular resistances, the relaxation time and the distribution coefficient of the relaxation time. The EIS properties of the leaves changed significantly during the growing season when new leaves were expanding. The clones differed in their EIS properties. Clone 4 had a significantly higher extracellular resistance and distribution coefficient than Clone 80. The clones responded similarly to the fumigation treatments. Differences between treatments emerged especially during the second fumigation season in 2000. Elevated [O3] reduced both the relaxation time and the extracellular resistance, indicating cell membrane damage. Elevated [CO2] increased the intracellular resistance, indicating changes in symplastic composition. The biological interpretation of the EIS parameters in birch leaves is discussed.

Improved spice models of aluminum electrolytic capacitors for inverter applications

Impedance modeling of aluminum electrolytic capacitors presents a challenge to design engineers, due to the complex nature of the capacitor construction. Unlike an electrostatic capacitor, an electrolytic capacitor behaves like a lossy coaxial distributed RC circuit element whose series and distributed resistances are strong functions of temperature and frequency. This behavior gives rise to values of capacitance, ESR (effective series resistance), and impedance that vary by several orders of magnitude over the typical frequency and temperature range of power inverter applications. Existing public-domain Spice models do not accurately account for this behavior. In this paper, a physics-based approach is used to develop an improved impedance model that is interpreted both in pure Spice circuit models and in math functions.

Coupled resonator distributed-element circuits for monolithic crystal filters

The distributed-element equivalent circuit of the monolithic crystal filter is useful for analyzing the characteristics of the filter, but it is not suitable for physical interpretation of the filter behavior. A more refined coupled resonator circuit is derived by application of a sequence of transformations of the original distributed-element circuit. The frequency dependences of the circuit elements are discussed and some approximations of the equivalent circuits are introduced based on the discussion. Moderately wideband filters are designed using an approximate circuit.

Small‐Signal AC Response of an Electrochemical Cell with Completely Blocking Electrodes

An exact solution is presented for the small‐signal ac response, in the continuum approximation, of an electrochemical cell, or half‐cell, with unsupported electrolyte and completely blocking electrodes. The solution includes the possibility of inner layer capacitance effects, arbitrary mobilities, arbitrary valence numbers, and any degree of charge dissociation. It applies to liquid and solid electrolytes, fused salts, and even intrinsic semiconductors. Numerous complex plane plots are included to demonstrate some of the many types of response possible. The present solution has also been incorporated as a distributed circuit element for use in equivalent circuit fitting using a newly improved complex non‐linear least squares fitting program.

Some simple equivalent circuits for ionic conductors

Some equivalent circuits which involve one or two distributed circuit elements are discussed. These circuits are useful in fitting small-signal frequency response data for solids and liquids. A fitting circuit recently proposed by Bruce to represent distributed bulk effects in conducting materials is shown to be closely related to earlier work. Although Bruce demonstrated that his circuit fitted certain data better than a simple alternative circuit, it is not physically realistic in the high frequency region. We investigate how well the response of the Bruce circuit (which involves one distributed circuit element and three ideal elements) can be simulated by that of simpler circuits, ones which involve a single unified distributed element, possibly in parallel with a single ideal capacitor. The usefulness of several different distributed elements, most of which have been widely used for data fitting in the past , is compared. Complex nonlinear least squares fitting results suggest that several of the simpler circuits considered are preferable to the proposed Bruce circuit for fitting of most ionic-conductor frequency response data. Finally, two structurally different equivalent circuits which involve two distributed elements each, so they can represent distributed interface as well as bulk effects, are compared and found to be able to simulate each other quite well under certain conditions. Problems which thus arise in choosing the best equivalent circuit for data fitting are discussed.