A Wideband Termination Based on Laser-Scribed Lossy Microstrip Line Structures

Laser-direct writing has become an alternative method to fabricate microwave devices. We present a laser-scribed wideband open-end termination that relies on conductor loss of the microstrip line structure to obtain effective absorption. The proposed design consists of a resistive film overlapped on a strip conductor, providing an enlarged sheet-resistance range (20 Ω/□ ~ 1.2 kΩ/□) of the resistive film to reduce the fabrication difficulties. The resistive film is in tapered shape to enable small gradual changes in impedance, yielding minimized reflections (|S11|). The prototype is demonstrated utilizing the laser-direct writing technique, with a measured |S11| over −15 dB from 6 GHz to at least 30 GHz. The termination can also be used for attenuation over a −10 dB attenuation level (>8.5 GHz) with a low reflection level better than −15 dB (>2.0 GHz). This study can be employed for the applications where cheap wideband planar terminations are needed and promote fast, flexible, and low-cost prototyping or modification of the existing microwave circuits.

An ultra-wideband rectangular ring dielectric resonator antenna integrated with hybrid shaped patch for wireless applications

A new wideband omni-directional compact rectangular ring dielectric resonator antenna (RRDRA) fused with slotted bevel shaped patch antenna is presented for the ultra-wideband (UWB) applications. The RRDR (rectangular ring dielectric resonator) is employed to generate lower order radiating modes with merge with the modes of patch to obtain high impedance bandwidth in UWB region. Further, RRDR use led to reduction in overall conductor loss to achieve high radiation efficiency. The proposed RRDRA structure achieved an impedance bandwidth covering the frequency range from 2.6–15.6 GHz, or ∼142%. The measured results show that the proposed DRA provides peak measured gain of 6.2 dBi and radiation efficiency of 90% at resonant frequency 6.3 GHz with stable omni-directional monopole like radiation patterns with low cross-polarization. The proposed antenna has a short ground plane of size 40 × 40 × 11.6 mm3 or ∼0.34λ 0 × 0.34λ 0 × 0.10λ 0 at 2.6 GHz.

Terahertz rectangular waveguides with inserted graphene films biased by light and their quasi-linear electromagnetic modeling

Novel rectangular waveguides with graphene inserts biased by light are proposed herein. The graphene films short the conductor plates of waveguides and support the localized transverse-electric modes. Their electric fields are parallel to the wide walls of these waveguides, and the eigenmodes have decreased conductor loss. The designs do not involve the conductor and graphene strips with their sharp edges, and the loss associated with the current crowding effect is excluded. The waveguides are treated in the quasi-linear regime using a rigorous field matching method, and the complex dispersion eigenmodal equation is solved using a validated iteration algorithm. At the terahertz frequencies of amplification, where the real part of graphene conductivity is negative, a gain increase is found with the eigenmodal number. This gain can be tuned by the waveguide geometry, dielectric filling, and the level of quasi-Fermi energy. The ideal waveguide theory is corrected using a perturbation approach and the Drude model of surface resistance of waveguide plates.

Graphene H-Waveguide for Terahertz Lasing Applications: Electromagnetic Quasi-Linear Theory

A novel graphene H-waveguide is proposed for active terahertz components. A graphene film illuminated by strong pumping light shorts the parallel conductor plates. The terahertz modes propagating along this film are amplified at certain conditions. A rigorous electromagnetic (EM) quasi-linear method of analytical calculations of TEy and TMy eigenmodes is used in this paper to select these conditions. Among them is the use of bound TEy modes interacting with graphene plasmons at frequencies of negative graphene resistance, minimizing conductor loss associated with parallel plates, and excluding the current-crowding effect from the waveguide design. The limitations of the used theory are considered, and the applications of this waveguide are proposed.

The influence of thermal properties on power transmission characteristics of HVDC cables – a factor analysis

<p>Power transmission capacity of HVDC cable links depend to a large extent on the voltage level but also on operating temperature and consequently conductor cross-section. A high operating temperature offers larger transmission capacity at a given conductor crosssection. However, an increasing temperature will also<br />increase the conductor loss and the associated costs. The most beneficial design choice is seldom straightforward and involves a trade-off between several design parameters. In this paper the influence of thermal properties of the insulating material and the surrounding soil, as well as operating temperature and conductor cross-section, is investigated by means of factor analysis with respect to important criteria such as transmission capacity, loss and associated cost of operation. This approach is chosen in order to separate different influencing factors as well as elucidating the interaction between said factors.</p>