Scarce-resource capacity sharing in cognitive radio environments: a new game theoretical model

This paper proposes a novel model of the input impedance of a circular-loop antenna based on wave equations. A circular-loop antenna is equivalent to uniform parallel double wires with losses and a short circuit load. The characteristic impedance, the propagation coefficient and the inductance, capacitance and resistance per unit length of the uniform parallel double wires with losses can first be expressed as closed solutions, and the mathematical model of the input impedance of the circular-loop antenna can then be derived naturally from the wave equations. Comparison of the data curve from this model with curves from simulations and experiments show that they are similar; however, some discrepancies are observed, and are attributed to the estimation error of the radiation resistance of the circular-loop antenna. As long as the circular-loop antenna is made from an isotropic material and its size remains uniform, the equivalent method is valid electrically for both small- and large-sized circular-loop antennas.     

提高压电换能器导纳圆测量精度的方法研究

不同压电换能器的动态电阻、电容、电感和静态电阻、电容的值不同,这些参数均可从其对应的导纳圆中得到.分析了导纳圆测量中的两个重要影响因素:A/D转换器的量化误差、测量电阻.为提高导纳圆的测量精度,量化误差不变时不同的压电换能器需选择不同的测量电阻以保证所测量的两路正弦信号有适当的幅值比和相位差.测量电阻的值为压电换能器动态电阻值的0.15～3.5倍时,导纳圆半径的相对误差小于0.5％,测量电阻为动态电阻的0.7倍时导纳圆的相对误差最小.     

T形天线的研究

系统地研究位于山谷间T形天线的电特性.采用矩量法求解天线和地面上的静电荷分布密度及电流分布密度,进而计算了T形天线与地面之间的静电容和天线的输入电抗,数值结果与实验结果吻合良好.同时研究了引线及顶线的各项参数变化对天线的有效高度、增益、输入电抗、辐射电阻及静电容的影响.研究表明,增加引线数目、引线间距和加长顶线长度均可以增加天线系统的静电容,减小输入电抗的模值,并使天线的增益有所改善.     

Subthreshold parameters of radio-frequency multi-finger nanometer MOS transistors

The subthreshold radio-frequency (RF) characteristics of multi-finger nanoscale MOS transistors were studied by using the measured scattering (s) parameters. Small-signal circuit parameters were determined based on a simplified small-signal equivalent circuit model. We found that besides the source and gate resistances, most of the parameters such as the channel resistance, drain inductance and intrinsic capacitance are found to be significantly different to those in the saturation mode of operation. The subthreshold channel resistance increases and the drain inductance decreases as the finger number increases because of the more significant charge transport along the finger boundaries. In addition, the channel resistance can be governed by the drain-induced barrier lowering in a transistor with very short gate length. The equivalent intrinsic capacitance of the small-signal equivalent circuit is governed by the substrate resistance and capacitance which make the parameter extraction more difficult.     

Equivalent circuits for electrically small antennas using LS-decomposition with the method of moments

As part of an investigation into methods for accelerating the process of filling the method-of-moments impedance matrix [Z], it was found that [Z] could be decomposed into three parts: a real inductance matrix [L] from the magnetostatic vector potential, a real elastance matrix [S] from the electrostatic static scalar potential, and a complex impedance matrix [z(ω)] of residual frequency-dependent contributions. By neglecting [z(ω)] at sufficiently low frequencies, static and quasi-static charge and current distributions were obtained. For electrically small antennas, a complete RLC circuit was obtained directly from a single quasi-static solution rather than as an approximate characterization of the impedance as a function of frequency. This gives a precise definition of the circuit parameters limiting the performance of electrically small antennas     

Geometric and Compaction Dependence of Printed Polymer-Based RFID Tag Antenna Performance

Radio frequency identification (RFID) tags with printed antennas are lower in cost but have lower performance than those with metal antennas. Printed antennas can replace metal ones if the performance is increased without raising cost. The performance of printed antennas can be increased if the series resistance in the antennas is lowered. The resistance is dependent on the line thickness and the resistivity of the conductive ink. Printed antennas with different line thicknesses were fabricated to investigate the effect of compaction and thickness on the resistance. The resistance of the printed antenna coils decreased by more than 40% after compaction, while the inductance and the parasitic capacitance were unchanged. RFIDs with compacted printed antennas were found to have significantly increased read range. RFIDs with thick printed antennas were fabricated and tested. These RFIDs were shown to have read ranges comparable to the RFIDs with copper wire antennas. Moreover, a geometry-independent plateau for the read range was found. The presence of a plateau is valuable for thick-line printed antenna since the plateau will enable the usage of low precision printing techniques to lower tag fabrication cost.     

准分子激光器参数测量

测量了快放电激励氟化氙准分子激光器的激光脉冲波形和放电电流波形，并由此测出了激光器和放电球隙开关的动态电感和电阻。讨论了储能电容、器件的电感和充电电压对激光脉冲的影响。     

A superconductive tuner with broad tuning range

The tuner discussed in this letter is a superconductive, tunable, parallel LC resonant circuit. The inductance and capacitance are varied simultaneously. A tuning range of 17:1 in frequency has been achieved within a single band. Bandwidth can be controlled by coupling control. Q's in excess of 10⁵were measured.     

A discussion on the properties of electrically small self-resonant wire antennas

The performance properties of several electrically small, self-resonant wire antennas are compared as a function of their total wire length, geometry, and effective volume. The radiation properties considered include resonant frequency, radiation resistance, and quality factor (Q). It is shown that the resonant properties of these antennas are directly a function of the antenna's effective height and effective volume, which are established by both total wire length and geometry. When the total wire length and geometry of these antennas are configured such that the antennas exhibit the same effective height and volume, their resonant properties are essentially identical, independent of any differences in their total wire length and geometry. Both computed and measured data are presented to support the comparison of the antennas' resonant properties.     

On antenna impedances in a cold plasma with a perpendicular static magnetic field

A flat strip antenna is embedded in a magnetoionic medium with its longitudinal axis perpendicular to the static magnetic field. The antenna characteristics differ for antennas oriented with their surfaces parallel and perpendicular to the static magnetic field. In the former case there are no resistance peaks for frequencies near the plasma frequency and the reactance of a short antenna is capacitive for low frequencies. For frequencies near the gyrofrequency the antennas are electrically longer for the parallel orientation of their surfaces. The accuracy of the solutions is illustrated by computing the tangential electric surface fields that are excited by the approximate current distributions used in the impedance computations.     

Glottal impedance based on a finite element analysis oftwo-dimensional unsteady viscous flow in a static glottis

Unsteady viscous flows in various static models of the glottis are numerically simulated using a finite-element method, and parameters of the electrically equivalent impedances in the models are determined. Different shapes of the static models, which are obtained by varying the angle and diameter of the glottis, produce flow patterns quite different from each other. Really complicated flow patterns have been obtained with the help of appropriate preprocessing/postprocessing software. The equivalent glottal impedance parameters are evaluated. The equivalent resistance values are compared with those derived by previously proposed formulas, and the equivalent inductance values are compared with the analytic solution derived from the Navier-Stokes equations. The present results closely approximate real flow measurements already reported, thus indicating that the numerical method approximates the real phenomena and is therefore useful for the analysis of vocal sources     

A new class of electrically small antennas

This paper describes a new class of electrically small antennas, of which the principal advantages are the resistive input impedance, the radiation resistance transformation which may be obtained within the structure, and the variety of shapes which the antennas may take. The antennas incorporate resonant half-wave windings, and a simple transmission line theory is presented by which antenna efficiency and bandwidth may be calculated. Experimental methods and results are described for antennas in the order of 0.01 wavelength in height and 0.05 wavelength in diameter.     

Tunnel-diode junction capacitance measurement

This paper describes a basic HF (as contrasted to VHF or microwave frequency) substitution technique for measurement of tunnel-diode junction capacitance. This technique was devised to solve the problem of series lead inductance errors resulting from the high conductance of these diodes and the resultant fractional Q's of their junction capacitances in the HF region. The paper also describes an extension of this technique which has made possible the determination of diode capacitances as low as 2 µµf in the negative resistance region for diodes having time constants<10^{-10}with an uncertainty of less than ±0.25 µµf.     

Effective Capacitance of Inductive Interconnects for Short-Circuit Power Analysis

Interconnect resistance and inductance shield part of the load capacitance, resulting in a faster voltage transition at the output of the driver. Ignoring this shielding effect may induce significant error when estimating short-circuit power. In order to capture this shielding effect, an effective capacitance of a distributed RLC load is presented for accurately estimating the short-circuit power. The proposed method has been verified with Cadence Spectre simulations. The average error of the short-circuit power obtained with the effective capacitance is less than 7% for the example circuits as compared with an RLC model. This effective capacitance can be used in look-up tables or in empirical -factor expressions to estimate short-circuit power.     

Metamaterial-based efficient electrically small antennas

A metamaterial paradigm for achieving an efficient, electrically small antenna is introduced. Spherical shells of homogenous, isotropic negative permittivity (ENG) material are designed to create electrically small resonant systems for several antennas: an infinitesimal electric dipole, a very short center-fed cylindrical electric dipole, and a very short coaxially-fed electric monopole over an infinite ground plane. Analytical and numerical models demonstrate that a properly designed ENG shell provides a distributed inductive element resonantly matched to these highly capacitive electrically small antennas, i.e., an ENG shell can be designed to produce an electrically small system with a zero input reactance and an input resistance that is matched to a specified source resistance leading to overall efficiencies approaching unity. Losses and dispersion characteristics of the ENG materials are also included in the analytical models. Finite element numerical models of the various antenna-ENG shell systems are developed and used to predict their input impedances. These electrically small antenna-ENG shell systems with idealized dispersionless ENG material properties are shown to be very efficient and to have fractional bandwidths above the values associated with the Chu limit for the quality factor without any degradation in the radiation patterns of the antennas. Introducing dispersion and losses into the analytical models, the resulting bandwidths are shown to be reduced significantly, but remain slightly above (below) the corresponding Chu-based value for an energy-based limiting (Drude) dispersion model of the permittivity of the ENG shell.     

Experimental study of an inductively loaded short monopole antenna

Theoretical studies have shown that the properties of electrically short monopole antennas are improved by placing an inductive load on the structure. The results obtained from the moment method are presented and compared with an experimental evaluation. The current distribution along the structure is computed and measured for various positions of the load. From this, the input admittance, efficiency, and bandwidth of the antenna are deduced. It is found that the efficiency and the bandwidth of the antenna increase as the load is moved from the base of the monopole until a maximum is reached. Simultaneously, the value of the inductance required to tune the monopole increases as the latter is moved away from the base.     

The Electrically Small Multi-Turn Loop Antenna with a Spheroidal Core

A complete analysis of the electrically small multi-turn loop antenna with a spheroidal core is presented, using quasistatic electromagnetic theory (QS). Its use as a primary design tool for later use in conjunction with a large finite-element (FEM) program for full-wave analysis of a practical loop with a cylindrical core is illustrated. Previously unavailable components of the equivalent circuit, including conductor and core losses, inductance, and capacitance, are derived. The accuracy of this circuit for practical use is demonstrated by comparison with results obtained from an FEM analysis of a cylindrical loop of equal volume and aspect ratio. All results are obtained in closed form: these include expressions for the dependence of the impedance, bandwidth, and efficiency upon the frequency, volume, aspect ratio, permeability, and number of turns. Although attention is focused on the design of a 2 MHz transmitting antenna, the theory is sufficiently general for application to the design of electrically small receiving or transmitting antennas at other frequencies     

Analysis of Umbrella antenna at the Omega navigation station

The characteristics of the electrically very small umbrella antenna used for the Omega navigation system are examined by the numerical analysis. The transmitting antenna of height about0.02 lambdawith 16 inclined elements at the Tsushima station is analyzed as an example of electrically very small umbrella antenna. In the analysis the ground is assumed to be a perfectly conducting plane and the Hallen-type integral equation is used. The difference between the calculated input resistance and the measured one is estimated as the earthing resistance. The approximate equation of radiation resistance is derived and the relation between the inclined elements and the antenna characteristics is discussed.     

Shielding effect of on-chip interconnect inductance

Interconnect inductance introduces a shielding effect which decreases the effective capacitance seen by the driver of a circuit, reducing the gate delay. A model of the effective capacitance of an RLC load driven by a CMOS inverter is presented. The interconnect inductance decreases the gate delay and increases the time required for the signal to propagate across an interconnect, reducing the overall delay to drive an RLC load. Ignoring the line inductance overestimates the circuit delay, inefficiently oversizing the circuit driver. Considering line inductance in the design process saves gate area, reducing dynamic power dissipation. Average reductions in power of 17% and area of 29% are achieved for example circuits. An accurate model for a CMOS inverter and an RLC load is used to characterize the propagation delay. The accuracy of the delay model is within an average error of less than 9% as compared to SPICE.     

Addendum to "Increased capacitance for VLF umbrella antennas using multiple-wire rib construction"

A computed value of static capacitance for a 300-ft umbrella antenna with twelve 9-in diameter multiple wire-ribs is presented and compared with measured capacitances of both fractional- and full-scale models of this structure. In addition, the computed values of static capacitance of this umbrella antenna are presented for rib diameters offrac{1}{4}to 48 in which indicate capacitance increases of approximately 50 percent.