Efficient transient analysis of nonlinearly loaded low-loss multiconductor interconnects

The combined time- and frequency-domain analysis of nonlinearly loaded low-loss interconnects is addressed. We show that a variety of interconnects commonly employed in different technological applications are characterized by transfer functions, whose impulse responses have a fast initial-time structure (due to the skin effect) and a slow long-time part (due to ohmic losses). The dependence of the impulse response structure on the line parameters is discussed, along with the exact analytical solutions valid for the skin effect and ohmic losses, separately. A piecewise linear approximation of the transient functions with nonuniform sampling is proposed as an effective method to obtain high accuracy at low computational costs. Various numerical examples are used to validate the effectiveness of the proposed representation, and to show that a matched characterization of the line must be adopted in order to avoid numerical artifacts.     

Transient response of a layer of discrete random media over adielectric half space

A solution is presented in the time domain for the scattering of a short pulse incident on a layer of discrete random media. The layer consists of identical, but randomly oriented particles situated above a homogeneous (i.e. deterministic) half-space. A solution is found for the backscattered pulse when the incident pulse is obliquely incident on the layer. The solution is obtained in the case of low particle density using the distorted Born approximation. The short pulse solution is an approximation to the impulse response (Green's function) for the layer and as such can be used to compute the response to pulses of arbitrary shape     

Genetic algorithms based analyses of nonlinearly loaded antenna arrays including mutual coupling effects

Initially, the analysis of a single nonlinearly loaded antenna is transformed into a nonlinear microwave circuit with the circuit elements representing the antenna element and the lumped load. This equivalent circuit is then reformulated into an optimization problem which can be solved by genetic algorithms. The analyses can also be easily extended to finite and infinite nonlinearly loaded antenna arrays including mutual coupling effects. Numerical examples show that the results by genetic algorithms are consistent with those using harmonic balance techniques. With the use of genetic algorithms, our analyses do not require a suitable guess of an initial solution and there exists no gradient operations in the iteration procedures. Therefore, the analyses are suitable for problems of nonlinearly loaded antenna arrays with any types of lumped loads and the array mutual coupling effects are included.     

Radiation and scattering from thin wires in chiral media

The effect of chirality on thin wire antennas and scatterers in unbounded chiral material is examined through the application of fundamental principles and the examination of several canonical examples. In particular, the interplay between normalized chirality and wire length is investigated to classify radiation and scattering patterns. Chirality induces rapid decay in the currents on such wires, resulting in mountain-peak-shaped current distributions characteristic of wire antennas and bow-tie-shaped distributions characteristic of wire scatterers of sufficient length. These current distributions, in turn, cause radiation and scattering patterns which exhibit a chirality-dependent forbidden zone for both antennas and scatterers. In this zone, the fields are greatly reduced. These distinctive results lead naturally to the classification of wire scattering and radiation into subchiral, chiral, and superchiral regimes. All results are understood from the underlying physical principles of electromagnetic chirality, and are related to values of a dimensionless parameter involving normalized chirality and normalized wire length     

Transient response of a microwave beam amplifier

A model of a beam amplifier consisting of a chain of lightly-coupled cavities has been studied for initial time response with the aid of a computer. The beam flows through the center-holes of 20 cavities stacked together and coupled so the pass band width would be 5 per cent in an infinitely long chain. The intermediate cavities are externally loaded for stability. The electronic transit angle for each cavity is 3π/4,omega_{q}/omega = 0.1, and the beam-circuit coupling coefficient CBis small. Computations have been made of the steady-state input resistance, gain and bandwidth around the 3π/4 "cold" circuit phase shift frequency, as well as of the transient response for t ≥ 0. Results show 1) at the 3π/4 frequency the voltage in the output cavity overshoots the steady-state value, and reaches its first peak at a time almost exactly equal to the amplifier length divided by the group velocity; 2) at a frequency nearer to cutoff, for which the group velocity is smaller, the voltage does not overshoot, but approaches the steady-state value asymptotically, such that at a time equal to the amplifier length divided by the group velocity the voltage has about 80 per cent of its steady-state value.     

Transient response of a class of nonlinear systems

An algorithm is given to be used in conjunction with the parameter-plane method and the describing-function method for rapid calculation of transient oscillations in the design of a class of nonlinear systems.     

Transient response of a static VAr shunt compensator

A typical static VAr shunt compensator has been analyzed so that the step response and steady-state errors can be identified. The results show that the steady-state error is dependent upon the error in the measurement of the currents' phase alone. They also show that an unstable condition can occur, though it should rarely arise in practice. All the theory was verified on a low power (240 V, 3 A) system     

Transient response of a dipole over a circular ground screen

The time-domain response of a vertical electric dipole located over a circular ground screen is considered. The relevant time-harmonic solution is used as a starting point. By making a number of approximations a very simple formula is obtained for the transient response of the far field when the dipole current moment is a ramp function of time. It is shown that for early times, the pattern response appears as if the ground screen were of infinite extent, while at very long times, the response approaches that expected for a homogeneous flat ground.     

Finite-difference time-domain analysis of a complete transverseelectromagnetic cell loaded with liquid biological media in culturedishes

Transverse electromagnetic (TEM) cells can be used for exposing biological culture specimens to electromagnetic fields and observing possible anomalous effects. The uniformity of field exposure is critical to quantifying the biological response versus the electromagnetic dose. Standing waves and other electromagnetic field nonuniformities can cause nonuniform exposure. This paper reports the results of high-resolution three-dimensional finite-difference time-domain (FDTD) simulations of a complete TEM cell designed for operation at 837 MHz. Several different cases were studied in which the number of culture dishes, the depth of the culture liquid, and the orientation of the culture dishes were varied. Further, the effect of the culture-dish glass bottom thickness and the meniscus of the liquid medium were examined. The FDTD results show that there is a significant nonuniform field and specific absorption rate (SAR) distribution within the culture medium for each case examined. Hence, biological dose-response experiments using the TEM cell should account for the possibility of strong localized SAR peaking in the culture media to provide useful data in setting exposure standards for wireless communications     

Parasitic array of two loaded short antennas

A double impedance loading technique is applied in the study of a parasitic array of two loaded short antennas, Approximate solutions for the currents in the array elements are obtained. It is demonstrated that the current distributions in the array elements can be appropriately modified by optimum impedance loadings to achieve significant improvement in radiated power or directivity. Theoretical predictions are verified closely by the results of an experimental study.     

Transient response of a peak voltage detector for sinusoidalsignals

A fast peak detector for constant frequency sinusoidal signals is proposed. This detector is based on the concept of the orthogonal function set. The theoretical response time of this detector is less than one-fourth of a cycle. When this detector is used, the transient response of the output voltage is different under different inception angles. The mathematical equations to describe transient phenomena are derived and simulated. Because its transient response performance is superior to the conventional sinusoidal amplitude detector used in an analog controller, it can improve the transient response performance of the controller. For practical applications, the effects of harmonics and frequency variation are also discussed, simulated, and tested     

Transient response of ARROW VCSELs

The transient response of antiresonant reflecting optical waveguide (ARROW) vertical-cavity surface-emitting lasers (VCSELs) is analyzed. It is found that under current modulation, the radiation loss of the transverse-leaky mode decreases during the state of the lasers but increases during the state. Numerical analysis shows that this variation in radiation loss is due to the carrier-induced refractive-index depression that arises from spatial-hole-burning of carrier concentration. It is noted that the increment in radiation loss during the state can be used to prevent net modal gain of the transverse-leaky mode from reacquiring threshold after turn-off. Hence, a new method to design ARROW, based on the variation in radiation loss, is proposed to eliminate the excitation of secondary pulsation in VCSELs. The influence of thermal lensing effects on the excitation of secondary pulsation during the state of the lasers is also investigated.     

Transient response of vidicon photoconductors

An expression for the rise and decay times of vidicon photocurrents as a function of incident illumination is derived for a certain class of vidicon photoconductors. The approach taken is semiempirical in that certain parameters in the derived expression are obtained directly from vidicon manufacturer's data sheets. Regults compare well with the manufacturer's published results.     

Transient response of sample-and-hold circuits

The transient response of sample-and-hold circuits with parabolic approximation of switch resistance is considered. As a rule, such a law gives a maximum guaranteed duration for the transient process (acquisition time).     

Transient response of good conductors

The transient response of free charge in a good conductor is considered from a macroscopic viewpoint. The results reemphasize the importance of the frequency dependence of conductivity in predicting charge relaxation. Moreover, the charge density exhibits an additional dependence upon the means of excitation which is consistent with relativistic principles.     

Transient response of an infinite cylindrical antenna in a dissipative medium

The transient solution of an infinite cylindrical antenna in a dissipative medium caused by an impulse excitation at a delta gap is obtained via an exact solution in the form of definite integrals and a simple asymptotic formula. This formula is used to obtain an integral for calculating the antenna current caused by a double exponential input voltage at the gap; furthermore, the resulting integral reduces to Sunde's classic result under the diffusion limit. These results are applied to the transient response of a buried wire subject to an electromagnetic pulse (EMP) or nearby lightning incident wave.     

Transient response of MS-DFB amplifier-filters

Time and spectral responses of a tunable three-contact distributed feedback (DFB) amplifier-filter obtained by feeding 50-ps optical pulses show the generation of a slow exponential falling tail (≈ 200 ps) in the output signal when the input pulses are spectrally narrowed. This phenomenon should limit the transfer bit rate of wavelength-filtered signals     

Transient response of a thin wire to a moving charged particle

The transient current on a thin wire induced by a charged particle moving parallel to the wire axis is studied. An explicit analytical solution for the induced current is obtained by utilizing the natural-mode method in conjunction with the method of asymptotic expansion. It is found that the solution can be split into two parts: one part consists of damped sinusoidal oscillations and the other exhibits quasistatic-like behavior. Numerical results are presented and compared with some selected results obtained directly by numerically solving a spacetime domain integral equation for the induced wire current.     

Transient response of a class of nonlinear sampled-data control systems

The particular form of the mathematical model which describes nonlinear sampled-data control systems gives a method of studying transient response of this process.     

Transient response of a transistor employing limited saturation device technique

Charge control analysis the transient behaviour of a transistor employing limited saturation device (LSD) technique has been presented. The calculated transient response has been compared with the corresponding experimental observations using epitaxial planar transistors and good agreement has been obtained.