Miniaturisation of planar microwave circuits by using resonant-type left-handed transmission lines

It is demonstrated that planar microwave circuits and components such as impedance inverters or power dividers, among others, can be compacted by using artificial left-handed transmission lines in their designs. Key to this size reduction is the possibility to control the electrical characteristics of these lines (namely electrical length and image impedance) over wide margins by means of a single cell structure. It consists of a microstrip line section with a series capacitive gap etched in the conductor strip and loaded with a complementary split rings resonator etched in the ground plane. A recently reported model of the artificial line is used as a first step in the design of the desired devices. To demonstrate the viability of the approach, several prototype device examples are provided, that is a 90deg impedance inverter and several power dividers with different topologies. A 50% size reduction (as compared to conventional devices) has been achieved by implementing the devices in conventional low loss microwave substrates, but further levels of miniaturisation can be obtained if the devices are fabricated on advanced technologies such as low temperature co-fired ceramic or multi chip module-deposited, among others     

Nonlinear Josephson left-handed transmission lines

In the paper, a new nonlinear left-handed transmission line (NLHTL) that incorporates arrays of Josephson junctions (JJs) is proposed. The nonlinearity of the newly developed Josephson left-handed transmission line (JLHTL) is due to the highly nonlinear nature of the JJs that provide the shunt inductances required to realise an LHTL. The current-voltage relationship of an array of JJs is utilised to realise an inductively tunable LHTL. Dispersion analysis along with the scattering parameters of the JLHTL are presented to study the left-handed behaviour of the JLHTL. Finally, harmonic generation of the proposed JLHTL is studied     

Matrix theorems of multiconductor transmission lines

Abstract

The purpose of this article is to present three matrix theoremes pertaining to the analysis of electrical multiconductor transmission lines. In principle, the formulations are also applicable to coupled mechanical systems.     

Ultrafast response of superconducting transmission lines

The authors report investigations of picosecond transient propagation on normal and superconducting transmission lines and results of a variety of lines that include YBa₂Cu₃O_7-x (YBCO) coplanar lines, a superconducting coaxial cable, and a dielectric-matched gold-line structure. A previously developed algorithm for analyzing transient propagation was used to identify the dominant mechanisms for signal distortion in most of these cases, and the essential properties of all tested to date are summarized for a direct comparison     

Left-handed transmission lines at millimetre and sub-millimetre wavelengths

Co-planar strip (CPS) transmission lines, aimed at operating up to sub-millimetre wavelengths, were periodically loaded by lumped capacitances and inductances in series and shunt configuration, respectively. Under this condition, propagation on the line is backward with group and phase velocities of opposite signs. The transmission lines were fabricated onto a quartz substrate by e-beam patterning and thin film deposition, silicon nitride and gold layers, on a deep sub-micron scale (~200 nm). A direct evidence of left-handedness between 160 and 380 GHz was achieved via the tracking of phase advance in a differential phase experiment using electro-optic sampling. The comparison between modelling results by electromagnetic full wave circuit analysis and experiment was performed in the time and frequency domains. It shows a good agreement in the dispersion characteristics and ultra-fast variations in the transmitted signals. At last, we took benefit of a lumped element fitting approach in order to discuss of the frequency capability of this non-resonant approach     

Theory of self-magnetically insulated vacuum transmission lines

It is assumed that vacuum transmission lines in the self-magnetic insulation regime feature a limiting current, whereby the trajectories of electrons at the wave front arriving at the anode are tangent to the surface. Under this assumption, the law of energy conservation in the system provides an equation for the relativistic factor γ_m corresponding to the voltage at the outer boundary of the electron layer that can be used for determining the main characteristics of a transmission line in the self-magnetic insulation regime.     

Temperature distribution along superconducting power transmission lines

A system of equations, describing the refrigerant's parameters (temperature and pressure) change, during its flow along a heated pipeline, for example along a superconducting power transmission line (SPTL), is derived.The possibility of a temperature maximum existing in the SPTL is found.The possibility, in principle, of ‘isothermal’ SPTL (with constant temperature, along its length) is shown. The most favourable refrigerant parameters' region for SPTL is determined.     

Measurements and calculation for magnetically coated strip transmission lines

Measurement of the transmission parameters of magnetically coated strip conductors over a ground plane show that the series componentsRandLvary rapidly with frequency. If these components are resolved into an alternative configuration consisting of a parallel and series arrangement, this frequency variation is almost entirely absent. Calculation of the pulse transmission properties is then made much simpler. Comparison between calculated and measured waveforms is illustrated. The alternative circuit also suggests a line termination consisting of a resistance and capacitance which, both calculation and observation confirm, leads to good rise-time and pulse amplitude maintenance.     

Reflection and transmission of normally incident full-vector X waves on planar interfaces

The reflection and transmission of full-vector X waves normally incident on planar half-spaces and slabs are studied. For this purpose, X waves are expanded in terms of weighted vector Bessel beams; this new decomposition and reconstruction method offers a more lucid and intuitive interpretation of the physical phenomena observed upon the reflection or transmission of X waves when compared to the conventional plane-wave decomposition technique. Using the Bessel beam expansion approach, we have characterized changes in the field shape and the intensity distribution of the transmitted and reflected full-vector X waves. We have also identified a novel longitudinal shift, which is observed when a full-vector X wave is transmitted through a dielectric slab under frustrated total reflection condition. The results of our studies presented here are valuable in understanding the behavior of full-vector X waves when they are utilized in practical applications in electromagnetics, optics, and photonics, such as trap and tweezer setups, optical lithography, and immaterial probing.     

Magnetic field shielding concepts for power transmission lines

High current carrying cables used in power transmission lines create strong magnetic fields in their vicinity. For ac lines at 50-60 Hz, the magnetic field is quasi-static and hence uncoupled from the electric field. Shielding of such low frequency magnetic fields is a challenge. In this paper, finite element modeling is used to study the effect of various shield geometries and shield materials around a current carrying wire. Two-dimensional analysis is sufficient for this problem because the cables are very long compared to the wire diameters. Shielding effectiveness, defined as the difference in the magnetic field intensity with and without the shield, is presented. It is concluded that a partial shield is the optimal design for shielding the region below the cable. To achieve this, the shield gap must be oriented above the high current wire     

Integrated transmission lines for magnetic thin film memories

The pulse transmission properties of integrated strip lines are examined for a structure that has been proposed for application in a large capacity, high-speed magnetic film memory. The lines are vacuum-deposited onto an insulated ground plane and are characterized by low impedances. Previous analyses, such as those given by Eastman and Chang, McQuillan, and Harloff, examine the effects of skin-depth losses in lines which are assumed to be perfectly terminated. In general, this type of analysis is insufficient for lines which are lossy and which have resistive terminations. The present analysis considers skin-effect losses in the ground plane and in the strip conductors separately and also includes the effect of reflections from resistive terminations. The influence of heavy magnetic loading of the transmission line due to the presence of magnetic film devices is examined in detail. A computer program, similar to the one described by Bertin, has been used to obtain numerical results for the pulse response of the transmission lines. Data are presented which demonstrate the influence of line geometry and material properties.     

Counterflow cool down of cryogenic power transmission lines

Cool down of cryogenic power transmission lines which use a counterflow cooling arrangement is investigated analytically, numerically, and experimentally. The results demonstrate that the cool down time, t_cd, is given by fx463-1 where U is the overall heat transfer coefficient between the go and return streams, l the length, and ? the mass flow rate. The accuracy and utility of a previously reported numerical cool down model are also confirmed by comparison with experiment.     

Foamy-dielectric lens transmission lines for millimeter and submillimeter wavelength range

The principles of the construction of transmission lines based on lenses made of a material with a nearly unity refractive index (foamy-dielectric lens transmission line, FDLTL) are formulated. The transmission characteristics of two FDLTL variants for 3-mm wavelength band have been studied. It is shown that FDLTLs possess low damping and feature wave propagation in a single-mode regime.     

基于图像传输的巡线机器人远程控制

基于无线局域网络的图像传输,从提高图像传输的实时性和连贯性着手,完成了巡线机器人远程控制方案的设计和实验。图像传输采用并行的处理方式,大大提高了传输的速度;分析了影响图像传输质量的因素,提出了增强图像传输品质和连贯性的方法,实现了在监控端根据图像方便地对机器人实施控制的设计,并通过实验验证了图像传输的实时性和远程控制方案的有效性。     

输电线路导线断线试验及数值模拟分析

通过构建连续3档输电线路段,进行了不同导线型号、不同覆冰厚度的导线断线试验,测试了不同工况下跨中点导线张力及跨中点横向位移时程,计算了不同工况下试验线路段的阻尼比,确定了不同工况下导线张力的动力冲击系数。试验结果表明,离断线位置越近,冲击效果越明显;覆冰越厚,动力冲击系数越小,无冰时的动力冲击系数明显高于覆冰时的数值。随覆冰厚度的增加,断线前初始张力逐渐增大,断线残余静态张力与初始张力的比值逐渐增大;覆冰断线时第1峰值张力大都接近初始张力。有限元模型中采用试验识别确定的阻尼比,完成了不同断线工况下的数值模拟,各个断线工况的残余静态张力和第1峰值张力与试验值基本一致,最大误差分别为5.6%和12.9%。     

In-depth analysis of reciprocal periodic structures of transmission lines

An in-depth analysis of lossless reciprocal periodic structures of transmission lines (TLs) is presented. Interestingly, it is found that periodic structures can provide both non-negative (NNCR) and negative characteristic resistances (NCR). In addition, the magnitude of the voltage reflection coefficient associated with an equivalent model of periodic structures terminated with passive loads can be less than or equal to unity for the NNCR case, and can exceed unity and even approach infinity for the NCR case. However, associated powers are still conserved for both cases. Furthermore, an alternative derivation based on shortand open-circuited terminations for determining characteristic impedances and propagation constant of equivalent TLs is also introduced. An example of finite periodic TL structures, providing both NNCR and NCR cases, with varying the number of unit cells is also given. In addition, implementation and measurement are set up to verify theoretical and simulated results. It is found that these results are reasonably in good agreement     

覆冰导线机械式冲击除冰模拟研究

采用ABAQUS有限元软件建立覆冰导线有限元模型,利用用户材料子程序VUMAT定义覆冰本构模型和删除破坏单元,实现冲击载荷作用下导线除冰过程的模拟。覆冰采用多孔弹性模型,并考虑温度和孔隙率对其力学性能的影响;引入拉伸破坏准则判断覆冰的破坏。对不同档数、档距、覆冰孔隙率、覆冰厚度、除冰时的温度、冲击载荷大小等情况下除冰过程的模拟分析表明,较小范围温度的变化对除冰率的影响很小,而其它因素对除冰效果的影响明显,在设计机械式冲击除冰装置时应予以考虑。     

Analytic solution of non-uniform transmission lines at low frequencies

A simple approximated analytical solution is introduced to analyse arbitrary non-uniform transmission lines (NTLs) at low frequencies. First, the differential equations of NTLs are written as a suitable matrix differential equation. Then, the matrix differential equation is solved to obtain the chain parameter matrix of NTLs. Later, the voltage and current of the line are obtained at any point using the obtained chain parameter matrix. Finally, the validation of the introduced solution is studied.