Types Of Transmission Lines Research Articles

Input impedance characteristics of coaxial slot antennas for interstitial microwave hyperthermia

In this paper, a transmission-line type of input impedance model originally developed by King et al. (1983) for the insulated dipole antenna embedded in a homogeneous dissipative medium is extended to the case of insulated coaxial slot antenna. Physical construction of the latter indicates the presence of additional current path(s) inside the feed line, which shall lead to the shortening of its resonance length. This effect is taken into account in the impedance model and verified by experiments. Furthermore, a simple strategy for optimizing the applicator's impedance-matching performance is also described and verified. Excellent agreements observed between theoretical and measured S/sub 11/ data indicate that these models can be relied upon when designing an efficient applicator for interstitial microwave hyperthermia.

Lumped-element switchable superconducting filters

A switchable superconducting band-stop filter consisting of a series of LC resonators is described. Each resonator can be switched on or off using a bias current to control the superconducting-to-normal resistance transition. The bandwidth of the filter can thus be varied in steps. In each LC resonator, the magnetic field of the inductor passes through the fingers of the interdigital capacitor, and so a simple model is developed for the combined structure. The LC sections are placed in a coplanar line, but the model can easily be adapted to other types of transmission line. Experimental results are given.

Analysis and design of novel structures of artificial transmission lines for MMIC/MHMIC technology

In this paper, some new types of artificial transmission lines, compatible with monolithic-microwave integrated-circuit/miniature hybrid-microwave integrated-circuit technology are presented. In the new designs, short subsections of different lines are connected together to achieve the needed performance of various transmission-line functions such as impedance transformation, power coupling, etc. Theoretical calculations are given and some typical design data are provided, including models of extremely low impedance lines, which are very practical in the design of microwave power amplifiers and oscillators using heterojunction bipolar transistors or high electron-mobility transistors. Calculation results are validated by simulations and experiments. The proposed structures are very flexible and can easily provide transmission lines with widely varying characteristics.

Frequency-modulation type magnetic field sensor using transmission-line magnetic device

A novel frequency-modulation type magnetic field sensor composed of transmission-line magnetic device and phase-shift type oscillator has been developed. The transmission line magnetic device consists of soft magnetic layers, dielectric layers and conductor lines, which operate as a distributed constant circuit. The transmission characteristics such as voltage-gain and phase are influenced by permeability change due to the external magnetic field applied to the magnetic layer. A transmission-line device developed by using Co based amorphous ribbon was used in the feedback circuit of a phase-shift type oscillator. The oscillation frequency of the oscillator increased with increasing magnetic field.

The flip-chip bump interconnection for millimeter-wave GaAs MMIC

The flip-chip bump interconnection structure has become popular for microwave and millimeter-wave package applications. This structure is expected to provide higher performance and a low cost packaging method. This paper presents the results of an evaluation of flip-chip assembled radio frequency (RF) devices. A coplaner transmission line type GaAs monolithic microwave integrated circuit (MMIC) was mounted on an aluminum oxide (Al/sub 2/O/sub 3/) substrate using the flip-chip thermal compression method. The electrical performance (S-parameter and noise figure) was measured and the reliability of the interconnection was tested. The changing rate of the characteristic impedance (Zo) of transmission line on bare-chip caused by bare-chip surface proximity to a substrate was simulated by finite element method (FEM) analysis. Flip-chip bonding conditions were fixed to keep the gap that less than 1% of Zo changing rate and sufficient bonding strength for reliability of interconnection. The DC characteristics of a 30 GHz, 60 GHz and 77 GHz band low noise amplifier (LNA) were the same before and after mounting, and the RF performance of the assembled MMIC was the same as the bare-chip without packaging. However, the influence of underfilling was observed. When epoxy resin was injected into the gap between the bare-chip and the substrate, the frequency band of the MMIC shifted to the low side. The reliability of the bump interconnection was excellent. The interconnection resistance did not change in a temperature cycle (-55/spl deg/C to +125/spl deg/C until 1500 cycle) test.

Analytical aspects of plane wave illuminated thin wires and slits

The paper deals with simple elementary approximations for the current and charge response on different straight wire structures, dipoles and short slits in the receiving case. After proof that transmission line equations are also valid for single wires without discontinuities, these equations are formulated including the incoming wave. They turn out have simple particular solutions that could be expected for the case, when the electric field is parallel to the wire, but holds true for the general case too. Satisfying the boundary condition at discontinuities (wire ends, lumped elements) gives rise to additional waves appearing as solutions of the homogeneous wave equation. The formulation of currents along and voltages across a slit, including an illuminating magnetic field at one side of the screen, leads again to transmission-line type equations and, consequently, to the inhomogeneous wave equation. As slits in screens are usually small in terms of wavelength, an approximative solution for the short slit will do. For this case, even closed-form expressions are possible for the magnetic near field.

A novel transmission-line type high frequency transformer using a fine-grain Mn-Zn ferrite [for ballasts

A novel transmission-line type high-frequency transformer has been developed by using a fine-grain Mn-Zn ferrite. The device consists of a fine-grain Mn-Zn ferrite core, polyimide insulator, copper planar winding and copper ground-plane, which operates as a distributed constant circuit. A quarter-wavelength transmission-line transformer with a large voltage-gain under high impedance termination has been investigated, and has been applied for high frequency power conversion.

Characteristics of microstrip transmission line on grooved dielectric substrate

ABSTRACT: This letter proposed a new type of microstrip transmissionline called the ‘‘groo ¤ ed microstrip line GML ’’ for low conductor and()dielectric losses. The proposed structure is realized by using a dielectricsubstrate containing ¤ ertical groo ¤ es. The corrugation in the dielectricsubstrate helps in reducing the concentration of the current on the strip,which in turn reduces the conductor losses in the transmission medium.In addition, partial remo ¤ al of the material from the dielectric substratereduces the dielectric loss as well. The method of lines MOL is used to()calculate the effecti ¤ e dielectric constant and the associated conductorand dielectric losses. Finally, a comparison of the computed results of thegroo ¤ ed microstrip line is made with those of a con ¤ entional microstripline. Q 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 17:55]57, 1998. Key words: microstrip line; method of lines; conductor and dielectriclosses; groo ¤ ed substrate 1. INTRODUCTION

Transmission characteristics of several kinds of closed groove waveguides for millimeter waves

An advantage of closed groove guide over open groove guide is attended. In this paper, the several kinds of closed groove guides including the trapezoidal-, elliptic- and parabolic-groove guides as new types of millimeter wave transmission lines are presented. Their dispersion and cut-off characteristics of the dominant mode are analysed and compared with ones of the closed V-and circular- groove guides by using the equivalent network method. The obtained results have important meaning in theoretical studies and actual applications of groove waveguides.

Characteristic impedance of a rectangular double-ridged TEM line

The characteristic impedance of a TEM transmission line, shaped as a double-ridged rectangular coaxial line, is analyzed in this paper as the customary transversal static problem. This type of transmission line is useful, for example, as a part of a cascaded transition between a double-ridged waveguide and a coaxial line. The solution of the transversal problem is achieved by dividing the cross-sectional region into distinct, separable regions, each one being characterized by closed-form Green's functions relating the flux function to the electric field. Surface-type integral equations are then formulated over the boundaries between the regions. Solution of these equations via the method of moments (MoM's) using the Galerkin choice yields the results for the characteristic impedance as a function of cross-sectional dimensions. Convergence of the solution is also studied.

Micromachined membrane filters for microwave and millimeter-wave applications (invited article)

Recent developments in micromachining techniques at the University of Michigan have resulted in novel high-performance low-loss filters for microwave and millimeter-wave applications. The idea is based on suspending the filters on thin dielectric membranes to eliminate dielectric loss and dispersion problems, resulting in a pure TEM mode of propagation and conductor-loss-limited performance. The dielectric membrane and the surrounding cavities are built using chemical etching in Silicon and GaAs wafers. The filters are therefore compatible with low-cost IC fabrication techniques and can be com- bined with planar diodes and transistors to result in active filter networks. Several state-of-the-art filters have been realized including 15-GHz and 20-GHz bandpass interdigi- tal suspended stripline filters, lowpass and bandpass microshield filters at 30 GHz and 90 GHz, microstrip 94-GHz bandpass filters, and a 250-GHz bandpass filter with 1.0-1.5-dB insertion loss. This article reviews the associated fabrication techniques, the different types of transmission lines achieved using this technology, and the measured performance from 15 to 350 GHz. The study concludes with a detailed description of the future work in this area. Q 1997 John Wiley & Sons, Inc. Int J Microwa'e Millimeter-Wa'e CAE 7: 149-166, 1997.

Spiral inductors and transmission lines in silicon technology using copper-damascene interconnects and low-loss substrates

Spiral inductors and different types of transmission lines are fabricated by using copper (Cu)-damascene interconnects and high-resistivity silicon (HRS) or sapphire substrates. The fabrication process is compatible with the concepts of silicon device fabrication. Spiral inductors with 1.4-nH inductance have quality factors (Q) of 30 at 5.2 GHz and 40 at 5.8 GHz for the HRS and the sapphire substrates, respectively. 80-nH inductors have Q's as high as 13. The transmission-line losses are near 4 dB/cm at 10 GHz for microstrips, inverted microstrips, and coplanar lines, which are sufficiently small for maximum line lengths within typical silicon-chip areas. This paper shows that inductors with high Q's for lumped-element designs in the 1-10-GHz range and transmission lines with low losses for distributed-element designs beyond 10 GHz can be made available with the proposed adjustments to commercial silicon technology.

Embedded transmission-Line (ETL) MMIC for low-cost high-density wireless communication applications

A new embedded transmission-line (ETL) monolithic-microwave integrated-circuit (MMIC) approach which allows flexibility in mixing different transmission-line types (i.e., coplanar and striplines) for maximum MMIC design flexibility and permits the feasibility of eliminating backside processing for low production cost is described. This ETL MMIC approach is an enabling technology allowing for low-cost batch fabrication, and high-density integration of microwave and RF components (including silicon mixed-signal products) for emerging wireless communication applications. Designs and performance results of a number of ETL MMICs are described in this paper.

An analytical thermal model for MR heads

In this work, we present an analytical study of temperature rise due to Joule heating in magnetoresistive heads. Using a transmission-line type model and proper boundary conditions, we derived an analytical formula, including thermal resistance, finite track width and conducting lead effects. Results show the temperature rise due to Joule heat is non-uniform along the MR track width direction: the temperature rise has its peak at the center and decreases rapidly off the track. The averaged temperature rise, which is what one measures experimentally, is 20% lower than the maximum temperature rise at 2 /spl mu/m track width. Although the temperature distribution also depends on thermal conductivities of both MR and lead materials, it more strongly depends on the thickness and thermal conductivity of the gap dielectric material.

Application of the eigenmode transformation technique for the analysis of planar transmission lines

The eigenmode transformation technique is formulated for the analysis of inhomogeneously filled shielded waveguides containing metal inserts. The permittivity of the filling medium may be an arbitrary function of the transverse coordinates. The method is based on expanding the electromagnetic field in terms of the eigenmodes of the corresponding empty shielding waveguide. The metal inserts have first the effect of linearly transforming the eigenmodes of the empty guide into those of the shielded waveguide containing the metal inserts (including the TEM-modes). Next the inhomogeneity of the filling medium is taken into account which leads to a proper matrix eigenvalue problem. In addition an alternative formulation is derived from a variational approach. Results of both formulations are compared for a shielded circular dielectric waveguide. The eigenmode transformation technique is applied to various types of planar transmission lines, i.e., coupled microstrip lines, finlines, and coplanar lines. The results are compared with those of other methods.

The electrochemical behaviour of leaded brass in neutral CL − and SO 4− media

The electrochemical behaviour of lead brass with different leaded content in neutral chloride and sulphate solutions was investigated using the EIS technique. For comparison, the behaviour of the pure components of the alloy was investigated under the same conditions. The corrosion process was found to proceed via oxygen reduction following a diffusion controlled mechanism. The Cu electrode showed a higher polarization resistance due to film formation during oxygen reduction. Zn and Pb showed markedly lower impedance values due to continuous dissolution. The two investigated brass alloys (1.8% and 3.5% Pb, respectively) showed higher impedance values indicating the passivation of the surface in the Cl − or SO 4 − media. Brass II was found to be more stable against corrosion indicating the beneficial effect of the lead content in the alloy. At cathodic potentials, the only process is the oxygen reduction. Anodic polarization leads to selective dissolution of Zn. At more positive potentials simultaneous dissolution of the alloy components with the deposition of Cu(I) salt takes place leading to the passivation of the alloy surface. At higher potentials, film breakdown occurs producing Cu(II) compounds whose diffusion control the corrosion process. At potentials higher than − 0.1 V, pitting corrosion was observed and a transmission line type in the impedance spectra was recorded.

Optimum designs for transmission line towers

A method for the development of optimized tower designs for extra high-voltage transmission lines is presented in this paper. The optimization is with reference to both tower weight and geometry. It is achieved by the control of a chosen set of key design parameters. Fuzziness in the definition of these control variables is also included in the design process. A derivative-free method of nonlinear optimization is incorporated in the program, specially developed for the configuration, analysis and design of transmission line towers. A few interesting results of both crisp and fuzzy optimization, relevant to the design of a typical double circuit transmission line tower under multiple loading conditions, are presented.

Novel two-dimensional transmission-line collection systems for photovoltaic power

Innovative two-dimensional transmission-line systems for collecting distributed photovoltaic power are presented in this paper. Based on transmission-line theory and controlling the phase of a.c. sources, the net power of the proposed transmission-line type network can flow towards the target load. The validity of the proposed system is confirmed by mathematical analysis and simulated results. This paper makes a contribution to the concept of networks for the collection of renewable energy.

Analysis of some coplanar transmission lines: Coplanar coupled lines, coplanar coupled striplines, and coplanar coupled lines with rectangular microshield

AbstractTwo types of coplanar transmission lines, rectangular microshield coplanar coupled lines (RMCCL) and coplanar coupled rectangular microshield lines (CCRML), are proposed for MMIC applications. These are developed from coplanar coupled lines (CCL) and coplanar coupled strip lines (CCS). Analytic formulas are presented for calculating the quasistatic TEM parameters of these coupled lines by means of exact conformal mapping techniques. Numerical results are also presented to illustrate the properties of these coplanar transmission lines. © 1995 John Wiley & Sons, Inc.

Quasi-optical unidirectional ferrite devices

The questions concerning design and study of quasi-optical (QO) ferrite unidirectional devices, based on two types of transmission line, namely hollow dielectric beamguide (HDB) and squire metal-dielectric waveguide (MDW) were considered.