Exponential Transmission Line Research Articles

Diferansiyel Evrim Algoritması Kullanılarak Eksponansiyel Hatlar ile Alçak Geçiren Filtre Tasarımı

In this work, Differential Evolutionary Algorithm (DEA), a novel and commonly used optimization algorithm in engineering problems, is applied for the design optimization of a low pass filter with exponential transmission lines. Basically the principle of DEA is similar to genetic algorithms techniques, however compare to meta-heuristic algorithms it has a much simpler algorithm structure and higher stability compare to its counterpart algorithms. For design optimization of low pass filter with exponential transmission lines, each of the transmission lines width and variation with its length are taken as an optimization variable for DEA. Firstly the unit microstrip transmission line model is chosen. After that, the optimal value of widths and lengths are obtained via DEA. The cost function of the DEA is based on the calculation of scattering parameters of candidate's solutions crossed the requested frequency bandwidth.

A no-tune no-match wideband probe for nuclear quadrupole resonance spectroscopy in the VHF range

Nuclear quadrupole resonance (NQR) spectroscopy is a method for the characterization of chemical compounds containing so-called quadrupolar nuclei. Similar to nuclear magnetic resonance (NMR), the sample under investigation is irradiated with strong radiofrequency (RF) pulses, which stimulate the emission of weak RF signals from the quadrupolar nuclei. The signals are then amplified and Fourier transformed so as to obtain a spectrum. In principle, narrowband NQR spectra can be measured with NMR spectrometers. However, pure NQR signals require the absence of a static magnetic field and several special applications require the characterization of a substance over a large bandwidth, e.g. 50–100% of the central frequency, which is hardly possible with standard NMR equipment. Dedicated zero-field NQR equipment is not widespread and current concepts employ resonating probes which are tuned and matched over a wide range by using mechanical capacitors driven by stepper motors. While providing the highest signal to noise ratio (SNR) such probes are slow in operation and can only be operated from dedicated NMR consoles. We developed a low-cost NQR wideband probe without tuning and matching for applications in the very high frequency (VHF) range below 300 MHz. The probe coil was realized as part of a reactive network which approximates an exponential transmission line. The input reflection coefficient of the two developed prototype probe coils is ≤ 20 dB between 90–145 MHz and 74.5–99.5 MHz, respectively. Two wideband NQR spectra of published test substances were acquired with an SNR of better than 20 dB after sufficient averaging. The measured signals and the SNR correspond very well to the theoretically expected values and demonstrate the feasibility of the method. Because there is no need for tuning and matching, our probes can be operated easily from any available NMR console.

Design, Realization, and Experimental Test of a Coaxial Exponential Transmission Line Adaptor for a Half-Impulse Radiating Antenna

This paper describes the simulation, design, realization, and experimental test of a tapered transmission line (TL) for adapting a broad-band impulse generator to a radiating antenna, for a frequency range of 50 MHz-1 GHz. Two different taper geometries are considered and discussed in the analysis: exponential and logarithmic. Two analysis methods are also used: 1) analytical equations obtained by applying the TL theory and 2) full-wave numerical simulations in both frequency and time domains using Comsol. It is shown that, in general, an exponential taper performs better than a logarithmic one, particularly at high frequencies. Time-domain simulations reveal that, for fast transient subnanosecond pulses, both tapers can be used equivalently and the signal does not suffer from any significant distortion while traveling along the tapers. We also show that analytical equations obtained using the TL theory are in very good agreement with full-wave simulation results and can be used advantageously in the design of tapers. This paper also presents the mechanical design and the realization of an exponential taper used for the connection of a 50-Ω pulser to a half-impulse radiating antenna (HIRA) having an input impedance of 100-Ω . The realized taper is fully characterized in the frequency domain using a vector analyzer and in the time domain using a reflectometer and shown to be performing in agreement with the simulations.

指数传输线输出波形和传输效率的级数近似解

指数传输线输出波形和传输效率的级数近似解

PW级Ｚ箍缩驱动源指数传输线的电路模拟

PW级Ｚ箍缩驱动源指数传输线的电路模拟

Implementation of non-integer order integro-differential operators based on exponential type nonuniform long transmission lines

Implementation of non-integer order integro-differential operators based on exponential type nonuniform long transmission lines

On temperature control of buildings by adobe wall design: Duffin and Knowles' exponential transmission line model revisited

Duffin and Knowles (Solar Energy, Vol. 27(3), 1981) developed an equation for attenuation factor of an Adobe wall modelled as 4-terminal electrical transmission line network. The modelled electrical system and the derived formula for the real attenuation factor of the wall have been critically examined and then modified by taking into cognisance the true conceptualisation of a physical filter network as analogue of the thermal wall. By comparing results from the two versions of the exponential transmission line network models, it is shown that the effect of the correction on the attenuation factor is significant. Journal of the Nigerian Association of Mathematical Physics Vol. 10 2006: pp. 35-40

Response analysis on nonuniform transmission line

Transients on a loss less exponential transmission line with a pure resistance load are presented in this paper. The approach is based on the two-port presentation of the transmission line. Using Picard-Carson's method the transmission line equations are solved. The relationship between source voltage and the load voltage in s-domain is derived. All the results are plotted using program package Mathematica 3.0.

LLAMPÜDKEÑ: A high-current, low-impedance pulser employing an auxiliary exponential transmission line

The design and constructional aspects of a novel pulse power generator for use in dense plasma research presently under construction are presented. The generator consists of two Marx capacitor banks, each of 0.25 μF, 480 kV, and 28.8 kJ. Each Marx generator drives a water transmission line, in which the live electrode is the central conductor. The transmission lines consist of a constant impedance section followed by a multielectrode gas linegap followed by an exponential taper to the load section. The novel feature is the use of an auxiliary exponential line coupled at the load. This line controls both the voltage and the effective impedance at the load section. In addition, by leaving this line circuit open, energy not coupled to the plasma in the initial high-impedance phase may be reflected back and deposited into the discharge, increasing the peak current by 50%. Circuit simulations using a real-time-varying load impedance show that the current pulse rises in an approximately linear way to a maximum of 1.2 MA at 250 ns. The current falls to zero in the following 250 ns. The current waveform may be flattened simply by disconnecting the auxiliary line, giving a rectangular pulse of 350 ns with a maximum value of 950 kA. The overall impedance of the entire system may be adjusted by varying the separation between the conductors. The equivalent source impedance at the load is 0.8 Ω. This low value is by virtue of the auxiliary line, which limits the voltage at the load section and reduces the insulator constraints. We present simulations of the generator under real load conditions. The model also is checked against analytical solutions of exponential line behavior and against other published models of pulse power generators.

High speed driving of a gain-switched laser diode with an exponential transmission line

With the increase of information capacity of an airborne system, high speed driving of laser diodes have been of interest. In order to match the low resistive LD, proposed in this paper is an exponential transmission line, which is used as preshaping to compensate the pattern effect in gain switching of laser diodes. It also will be used to overcome the effect of parasitic elements in high speed driving to improve the rise and trail edges of the output waveform. An accurate circuit model of the exponential line for the PSPICE program has been developed and simulations are conveniently carried out by employing PSPICE.

Closed-form solution for lossy exponential transmission line problem in frequency and time domains

An exact and explicit solution for the reflection and transmission problem of a lossy exponential transmission line of finite length is derived in both the frequency and the time domain via a wave-splitting approach. The problem is formulated first in the frequency domain. Wave-splitting is defined and the solution for internal voltages and currents is derived. Closed-form solutions for the reflection and transmission coefficients are obtained. The explicit solution for a transmission line consisting of several exponential pieces (each with different taper) in series is then easily written down. To obtain the transient response of the lossy exponential line, a time domain Green function approach based on wave-splitting is used. Linear partial differential equations for the Green functions together with the initial and boundary conditions are derived and solved explicitly. The exact and explicit solutions for the transient reflection and transmission up to arbitrary large times are given.

Transient responses of an exponential transmission line and its applications to high-speed backdriving in in-circuit test

Step responses of an exponential line terminated with resistive loads are evaluated by means of time-domain scattering parameters. The results are used to illustrate the interaction between a nonuniform line and a nonlinear load. We find that an exponential line could be used to compensate the nonlinear load effects in high-speed backdriving. >

Transients on lossless exponential transmission lines using Allen's method

Exact analytical expressions for the time-domain step response matrix of the lossless exponential transmission line are developed, thereby extending the range of problems for which Allen's method can be applied for the transient analysis of networks consisting of interconnections of linear distributed elements, lumped linear and/or nonlinear elements, and arbitrary sources. An indication as to the correctness of the expressions is obtained by comparing them to published results, which also helps to give a better physical insight into the step response matrix. The response to a step input and the transient response to a sudden sinusoidal excitation are presented. >

On the existence of branch points in the eigenvalues of the electric field integral equation operator in the complex frequency plane

It is demonstrated by specific examples that eigenvalues of the electric field integral equation (EFIE) operator for finite extent objects in lossless media can have branch points in the complex frequency s -plane. Specifically, it is shown from the analysis of the spheroidal wave equation in the s -plane that branch points are present in the eigenvalues of the integral operator associated with the scalar scattering problem from a perfectly conducting spheroid. Similarly, it is concluded from the analysis of the Mathieu's differential equation that branch points, besides that associated with the infinite extent of the object, exist in the s -plane behavior of the eigenvalues of the EFIE operator for a perfectly conducting infinite elliptic cylinder. A proof is given that branch point singularities cannot occur in the eigenvalues of EFIE operators for structures in which geometrical symmetry completely determines the eigenfunctions (and hence they are frequency independent). It is conjectured that branch points may always be present when sufficient object symmetry is lacking. This conjecture is supported by the fact that branch points appear when a sphere is deformed into a spheroid or when a circular cylinder is deformed into an elliptic one. An analogous phenomenon has been observed in circuit and transmission line problems. For example, it is shown that when the taper parameter of an exponential transmission line goes to zero (the line becomes uniform and thus a symmetrical structure), the branch points in the eigenvalues of the impedance matrix move away to infinity.

The Design of Directional Couplers Using Exponential Lines in Inhomogeneous Media

Coupled exponential transmission lines in inhomogeneous media are analyzed and an accurate solution is obtained. The solution is used to design microwave directional couplers. The designed couplers have much improved coupling characteristics compared with couplers using uniform lines. Practical measurements show very good agreement with theoretical results.

Low-frequency wide-band impedance matching by exponential transmission lines

It is shown that by using an exponentially tapered transmission line in Ruthroff's connection it is possible to achieve impedance matching at low frequencies over a much wider band than is possible by using a uniform line. For a given ratio of load to source resistances, there is shown to exist an optimum set of line parameters for which the bandwidth obtained is a maximum.

Transient Analysis of Systems with Exponential Transmission Lines

Two computer solutions are given for pulse propagation along exponentially tapered transmission lines with arbitrary nonlinear sending and receiving networks. The solutions allow series and shunt loss terms per unit of length of the line. The method of characteristics is shown to be computationally superior to the cubic spline method in terms of accuracy and efficiency.

Normalized Impedance Graphs for Exponential Transmission Lines (Short Papers)

Sign errors in an existing closed form solution for the reflection coefficient along an exponentially tapered transmission line have been corrected and the solution has been modified by the use of electrical line length. This allows useful graphs for the input impedance of the tapered line to be computed which are normalized with respect to frequency and system impedance. The graphs clearly demonstrate both the broad-band and narrow-band properties of the tapered line.

Narrowband microwave filter using exponential lines

The formation of narrow passbands within the attenuating frequency range of an exponential transmission-line system is discussed theoretically and the results applied to form a small, simply tuned, bandpass filter.

Matrix Parameters of Coupled Exponential Lines

Various matrix parameters of coupled exponential transmission lines are presented and their applications in the analysis of certain coupled exponential line components are given.