Equivalent transformations for the mixed lumped Richards sectionand distributed transmission line

The authors introduce an analysis method for nonuniform transmission lines. Equivalent transformations between a circuit consisting of a cascade connection of a lumped Richards section, an ideal transformer, and a distributed transmission line and one consisting of a cascade connection of a class of a nonuniform transmission line, a lumped Richards section, and an ideal transformer, are given. Characteristic impedance distributions of these nonuniform transmission lines are expressed as hyperbolic or trigonometric functions. It is quite difficult to find the exact network functions of nonuniform transmission lines from the telegraph equation, but by using the equivalent transformation described it becomes possible to obtain exact network functions of a class of nonuniform transmission lines     

An equivalent transformation for the mixed lumped lossless two-portand distributed transmission line

It is shown that the circuit consisting of a cascade connection of a lumped type D section and a distributed transmission line is transformed to an equivalent circuit consisting of a cascade connection of a class of a nonuniform transmission line and a lumped type D section. Previously obtained equivalent transformations, i.e., Brune, type C, type A and type B sections, are included in the type D section transformation presented in this paper. The type D section is reduced into the Brune section and both type A and B sections are obtained as a degenerate case of the Brune section. Procedures for obtaining these transformations are given and a general theorem concerned with a mixed lumped lossless two-port and distributed transmission line transformation is established. By using these equivalent transformations, a new analytical method for nonuniform transmission lines is derived without having to solve the telegraph equations     

Multiport devices in transmission line models of lumped electroniccircuits

The analysis of nonlinear networks in the time domain by the transmission line method is potentially very efficient because of the decoupling of the nonlinear elements from the rest of the network by link transmission lines. The authors present new methods for modelling multiport devices and show how the standard transmission line analogy may be generalised to attain better efficiency     

传输线集总模型的严格理论推导

借助于负的集总电阻、电感、电导和电容的感念,本文建立了传输线系统的电路模型、双端口π型网络和T型网络模型。从传输线的N段梯形等效电路出发,应用连分数理论,获得了输入阻抗在输出端三种状态下(短路、断路和匹配)的表达式,进而得到了以集总参数RLGC给出的 表达式。再依据传输线的输入导纳公式、导纳矩阵和BACD矩阵,建立了传输线的集总电路模型、π型网络和T型网络模型,并分别在时域和频域进行了验证。     

拉丁方变换的几个等价刻划

给出了拉丁方变换的几个等价刻划,并给出了拉丁方变换的谱特征和差分特征。     

Extension of the transmission line matrix (TLM) method in itsapplication to lumped networks

An extension of the TLM method applicable to generalised lumped networks is outlined. It is shown from basic circuit theory that two separate branch admittance matrices are required to satisfy more general circuit conditions, as opposed to a single matrix for the more restricted cases studied previously     

基于广义传输线方程的矩形波导等效电路

介绍了广义传输线方程在波导分析中的应用,讨论了建立在该方程基础上的具有不连续性的矩形波导的等效电路,提出了用两个频点来提取整个频带内电路参数的方法,以加载金属膜片的矩形波导为例进行了数值计算,并应用等效电路来计算S参数,计算结果和用Ansoft公司的HFSS软件所得结果相符合.     

Approximation of a nonuniform transmission line by a cascade of uniform lines

It is shown that an arbitrary nonuniform transmission line may be approximated by a cascade of commensurate uniform lines. In general, a small number of lines is sufficient to obtain a good approximation, and hence the method should prove useful, both in the analysis of arbitrarily tapered lines and in the study of their properties.     

平面人工传输线等效集总参数经验公式的研究

平面人工传输线是一款性能良好的新型慢波结构,主要由弯曲线电感、交指电容等微带准集总元件构成。系统研究了弯曲线电感和交指电容的等效集总参数随结构参数变化的规律并给出反映这些规律的经验公式,考虑微带介质基板厚度和介电常数的影响,将所得经验公式进行修正使之适用于不同介质基板厚度和介电常数的情况,将修正的经验公式应用于基于平面人工传输线的威尔金森功分器的设计中。所得经验公式可用来快速、准确地设计平面人工传输线,对其他微带不连续或慢波结构的设计也具有参考意义。     

Pulse propagation along certain lumped nonlinear transmission lines

A lumped RGC transmission line having a switch in series with G (switch open for voltages greater than some fixed threshold; switch closed otherwise) and a shunt battery-resistor combination in each section is considered. It is shown that, although there exist two distinct resting states for each section, it is not always possible to switch the entire line from one state to the other, and it is never possible to propagate a pulse along such a line. Modifications are suggested in order to obtain pulse propagation.     

Highly nonlinear fiber-based lumped fiber Raman amplifier for CWDM transmission systems

The highly nonlinear fiber (HNLF)-based lumped fiber Raman amplifiers (LRAs) for four- and eight-channel coarse wavelength division multiplexing (CWDM) transmission systems have been investigated. By using the developed LRA, the four-channel CWDM transmission over conventional single-mode fiber (SMF) with the length of 150 km has been successfully achieved.     

Field solution of a type-II superconducting thin-film planarasymmetric transmission line in the mixed state

By using the electrodynamic field equations for a type-II superconductor in the mixed state, a sinusoidal wave solution is derived for an asymmetric high-T_c superconducting transmission line in the presence of vortices. This solution can be used to numerically demonstrate the dependence of the slow mode propagation on the temperature, frequency, and static magnetic field. The effects of vortices on propagation characteristics in a superconducting strip line are thus elucidated     

Cascade synthesis of transmission lines and lossless lumped networks

Considerable interest in mixed lumped/distributed networks has arisen in recent years. The use of semiconductor elements, which have essentially lumped equivalent circuits, in microwave networks is an obvious example, and the need to meet even more exacting filter specifications at ever higher frequencies has resulted in many problems which are essentially mixed lumped/distributed. In most applications, the cascade type of structure is required, and it has been claimed that the sufficient condition for a 2-variable bounded real reflection coefficient to be realised by a resistively terminated cascade of lossless transmission lines and lumped 2-ports is that the transmission zeros are the product of the transmission zeros of the basic sections. Primarily by a particular numerical example, it is shown that this result is not generally valid for a canonic cascade realisation. This result is because of the possibility of `dummy? sections existing within the network without violating the bounded-real condition at the terminals. Consideration of the existence of `dummy? sections leads to the conclusion that an additional n(n?1)/2 conditions are required, where n is the number of transmission matrices for both terminated and unterminated networks. Additional conditions for reciprocity etc. are given in the realisability conditions, which are entirely algebraic in nature.     

Codes for digital line transmission

Some ternary line codes using alternative codeword sets are described; it is shown that, compared with the currently accepted 4B3T codes, some reduction in redundancy can be achieved without increasing the digital-sum variation.     

Equivalent network for an aperture in the center conductor ofmicrostrip line

The equivalent circuits for discontinuities in the form of a thin transverse slot and a circular aperture in the center conductor of a microstrip line are determined by a quasi-static analysis using equivalent dipole moments. The series reactance as a function of frequency is evaluated in terms of the geometrical parameters of the discontinuity. Data obtained from transmission measurements are presented to support the theory     

Spectral estimation for the transmission line matrix method

The transmission line matrix (TLM) method for microwave circuit analysis calculates the time-domain variation of the electromagnetic fields in response to an arbitrarily chosen excitation. Spectral estimation for the TLM method by use of the discrete fourier transform and fast Fourier transform is reviewed. Error bounds are given and checked by means of a numerical example. A spectral estimation method based on Prony's method for use with TLM is presented. A numerical example shows that the method allows an order of magnitude reduction in the number of iterations in the TLM method for equal accuracy     

A safe transmission line for MRI

Magnetic resonance imaging (MRI) has been established as a reliable and safe imaging method for the human body. However, electric conductors, such as cables situated near or in the human body, should be avoided because induced currents in the cables can cause hazardous heating in the surrounding tissue. In this paper, a new principle for the design of a transmission line is introduced and demonstrated, which is capable of avoiding dangerous heating of cables. The principle is based on transformers placed along the line, splitting the long line into several short not resonant and thus safe sections. A transformer design is introduced along with the theoretical aspects for both the avoidance of the undesired induced currents and the reduction of signal attenuation. Furthermore, the design fulfills the geometrical requirements of the side lumen of a standard catheter. Matching networks, whose elements are determined by power matching, are used to reduce signal attenuation by the transformers. A prototype was built to validate both theory and the simulations. As demonstrated in this work, it is possible to build safe transmission lines for MRI, making applications such as active catheter tracking possible. We expect that even new applications, such as safe intravascular imaging will be possible in a safe manner in the future.     

Binary code suitable for line transmission

A practical method is described for encoding an unrestricted binary signal into a form suitable for transmission through a binary regenerated signal path while incurring only a small increase in modulation rate.     

Maximum transmission capacity of a soliton communication system with lumped amplifiers

For a soliton transmission system which uses lumped optical amplifiers with a fixed amplifier spacing and a fixed bit rate, the optimum input pulse width and input amplitude are presented to maximise the soliton transmission distance. In a 10 Gbit/s soliton system with a repeater spacing of 40 approximately 50 km, a pulse width of 20 ps, and an amplitude of 1.4 approximately 1.8, the limitation owing to mutual soliton interaction is negligible compared with that resulting from the interaction between amplifier noise and the soliton pulse, and the soliton pulse can propagate up to the Gordon-Haus limit.<>     

Natural frequencies of piecewise uniform transmission lines

A transmission line composed of a number of cascaded uniform lines with different characteristic impedances and lengths is considered. Approximate expressions for the chain parameters and natural frequencies useful to a variational synthesis are given.