Loaded Transmission Line Network Research Articles

Investigation of the plane wave coupling to a linearly loaded transmission line network

The article is concerned with a complex investigation of the influence of the plane wave coupling with a certain function of time, incident direction and polarization to a linearly loaded transmission line network comprised of three single-wire conductors with different lengths connected in the center. Line load is represented as 50 Ω resistors connected to all terminations of the transmission line network. The exemplary network was modeled on a computer and experimentally investigated in a gigahertz transverse electromagnetic GTEM cell, which allows creating an electromagnetic field of a certain direction. The coupled voltage at the terminals of the network was investigated in the frequency and time domains. To conduct an experiment in the frequency domain, both to create an electromagnetic field inside the GTEM camera and to measure the induced voltage at the terminations of the network, a vector network analyzer VNA was used. To conduct an experiment in the time domain for the sake of creating an electromagnetic field, a high-voltage voltage generator was used, whereas a strobing oscilloscope was used to measure the induced voltages. The simulation was performed in the LTspice software - a tool for calculating electrical and electronic circuits, and Matlab. It is also examined to show the compliance with the experimental results. On the basis of obtained results, the author was able to identify the main aspects that may be useful in modeling and predicting the electromagnetic processes occurring in linearly loaded conductors, power supply and / or data transmission systems.

Homogenization of tensor TL metamaterials

Abstract We present a method for homogenizing tensor transmission-line (TL) metamaterials. These are metamaterials consisting of loaded transmission-line networks, that can possess magnetically anisotropic (tensor) effective material parameters. The homogenization employs a local field averaging procedure to compute the effective material parameters. These effective material parameters can be dispersive or non-dispersive. For the tensor metamaterials possessing dispersive effective material parameters, the homogenization method takes advantage of the circuit topology of tensor transmission-line metamaterials to predict material parameters over a frequency range.

Anomalous reflection and refraction in anisotropic metamaterial realized by periodically loaded transmission line network

We have studied the electromagnetic wave propagation in two-dimensional anisotropic metamaterial (AMM) by realizing the AMM through periodic structure composed of anisotropically loaded transmission line (TL) network. The dispersion relation of the TL metamaterial is analyzed by rigorous periodic TL theory, which shows hyperbolic dispersion surface in phase space below certain critical frequency. Utilizing microstrip line technique, we have constructed an interface between isotropic normal medium and a particular type of AMM with properly designed normal TL mesh and the loaded TL network, respectively. The electromagnetic wave propagation in such system has been analyzed with the consideration of circuit losses using microwave circuit simulations. We directly demonstrate interesting phenomena including the total reflection with inversion of the critical angle at small incident angle as well as the oblique total transmission at large incident angle at the interface, which have good agreement with the theoretical prediction.

On Impedance Bandwidth of Resonant Patch Antennas Implemented Using Structures With Engineered Dispersion

We consider resonant patch antennas, implemented using loaded transmission-line networks and other exotic structures having engineered dispersion. An analytical expression is derived for the ratio of radiation quality factors of such antennas and conventional patch antennas loaded with (reference) dielectrics. In the ideal case this ratio depends only on the propagation constant and wave impedance of the structure under test, and it can be conveniently used to study what kind of dispersion leads to improved impedance bandwidth. We illustrate the effect of dispersion by implementing a resonant patch antenna using a periodic network of LC elements. The analytical results predicting enhanced impedance bandwidth compared to the reference results are validated using a commercial circuit simulator. Discussion is conducted on the practical limitations for the use of the proposed expression.

Negative refraction and partial focusing in an anisotropic metamaterial realized by a loaded transmission line network

We have studied the electromagnetic wave propagation in a two-dimensional anisotropic metamaterial (AMM) realized by a periodic structure composed of an anisotropically loaded transmission line (TL) network. The dispersion relation of the TL metamaterial is analysed by rigorous periodic TL theory, which shows hyperbolic dispersion surface in phase space below a certain critical frequency. We have constructed an interface between an isotropic normal medium and an AMM with a properly designed normal TL mesh and the loaded TL network, respectively, and analysed the electromagnetic wave propagation in such a system using microwave circuit simulations. We directly demonstrate the negative refraction of energy flow and the positive refraction of the wave vector, as well as the partial focusing phenomenon in such AMM, have good agreement with the theoretical prediction. When the dissipation is included in the simulation on actual microstrip line structure, we find that the dissipation in the TL metamaterial affects only the magnitude of the propagating energy, not the refraction phenomenon.

Practical limitations of subwavelength resolution using negative-refractive-index transmission-line lenses

Previously, we have demonstrated both analytically and experimentally subwavelength imaging using a negative-refractive-index lens made of a periodically L, C loaded transmission line (TL) network. This loaded transmission line network has been referred to as the dual TL lens. Here, we consider the limitations on subwavelength imaging imposed by impedance mismatches and the component losses of a practical dual TL lens. Simple expressions for estimating the resolving capability of a dual TL lens are given. It is found that the resolution enhancement of the dual lens is proportional to the quality factor of the series loading capacitors divided by the electrical thickness of the lens. The effective material parameters of the dual TL lens are also derived so that these expressions can be directly related to those of previous studies considering uniform and isotropic left-handed lenses. Finally, the resolving capability of an experimental lens that achieves subwavelength imaging is theoretically predicted. These theoretical predictions are then directly compared to previously reported experimental results.

A six-element beam-scanning array

A six-element beam-scanning coupled MESFET oscillator array was designed and constructed. Resistively loaded transmission line networks were used to strongly couple each oscillator to its two nearest neighbors. Measured H-plane radiation patterns indicate continuous scanning from /spl minus/30 to +40 degrees (from broadside).< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Approximation for the response of capacitively loaded transmission-line networks in the time domain

An approximate procedure for determining the time response of networks containing transmission lines terminated by lumped capacitive and resistive elements is outlined. It is possible to reduce the capacitively loaded system to a simpler form with purely resistive loads which can be handled using a graphical method.