Precise microwave characterization of MgO substrates for HTS circuits with superconducting post dielectric resonator

Accurate data of complex permittivity of dielectric substrates are needed for efficient design of HTS microwave planar circuits. We have tested MgO substrates from three different manufacturing batches using a dielectric resonator with superconducting parts recently developed for precise microwave characterization of laminar dielectrics at cryogenic temperatures. The measurement fixture has been fabricated using a SrLaAlO3 post dielectric resonator with DyBa2Cu3O7 end plates and silver-plated copper sidewalls to achieve the resolution of loss tangent measurements of 2 {\times} 10-6. The tested MgO substrates exhibited the average relative permittivity of 9.63 and tan {\delta} from 3.7 {\times} 10-7 to 2 {\times} 10-5 at frequency of 10.5 GHz in the temperature range from 14 to 80 K.Comment: 6 pages, 8 figures, 3 table

Introduction : screen Londons

Our aim, in editing the ‘London Issue’ of this journal, is to contribute to a conversation between scholars of British cinema and television, London historians and scholars of the cinematic city. In 2007, introducing the themed issue on ‘Space and Place in British Cinema and Television’, Steve Chibnall and Julian Petley observed that it would have been possible to fill the whole journal with essays about the representation of London. This issue does just that, responding to the increased interest in cinematic and, to a lesser extent, televisual, Londons, while also demonstrating the continuing fertility of the paradigms of ‘space and place’ for scholars of the moving image1. It includes a wide range of approaches to the topic of London on screen, with varying attention to British institutions of the moving image – such as Channel Four or the British Board of Film Classification – as well as to concepts such as genre, narration and memory. As a whole, the issue, through its juxtapositions of method and approach, shows something of the complexity of encounters between the terms ‘London’, ‘cinema’ and ‘television’ within British film and television studies

Political masculinities, crisis tendencies, and social transition: Toward an understanding of change

This introduction to the special issue on “Political Masculinities and Social Transition” rethinks the notion of “crisis in masculinity” and points to its weaknesses, such as cyclical patterns and chronicity. Rather than viewing key moments in history as points of rupture, we understand social change as encompassing ongoing transitions marked by a “fluid nature” (Montecinos 2017, 2). In line with this, the contributions examine how political masculinities are implicated within a wide range of social transitions, such as nation building after war, the founding of a new political party in response to an economic crisis, an “authoritarian relapse” of a democracy, attempts at changing society through terrorism, rapid industrialization as well as peace building in conflict areas. Building on Starck and Sauer’s definition of “political masculinities” we suggest applying the concept to instances in which power is explicitly either being (re)produced or challenged. We distinguish between political masculinities that are more readily identified as such (e.g., professional politicians) and less readily identified political masculinities (e.g., citizens), emphasizing how these interact with each other. We ask whether there is a discernible trajectory in the characteristics of political masculinities brought about by social transition that can be confirmed across cultures. The contributors’ findings indicate that these political masculinities can contribute to different kinds of change that either maintain the status quo, are progressive, retrogressive, or a mixture of these. Revolutionary transitions, it seems, often promote the adherence to traditional forms of political masculinity, whereas more reformatory transition leaves discursive spaces for argument

An UWB planar out-of-phase power divider employing microstrip-slot and parallel stripline-microstrip transitions

The design of a planar out-of-phase power divider with an ultra wideband (UWB) performance is presented. The device employs two substrates with a common ground plane. A coupling between two microstrip lines on the top and bottom substrate layers through a slot in the common ground plane, and a transition from two microstrip lines to a parallel stripline are used to achieve an UWB operation. The simulated and measured results of the proposed divider reveal low insertion losses, good return loss at the three ports and fine isolation between the two output ports across the band 3.1 to more than 11GHz with high phase stability. Copyright 2006 IEICE

Temperature dependence of complex permittivity of planar microwave materials

Fabrication of dielectric materials with low losses at microwave frequencies and stable dielectric properties under varying temperatures is an important and challenging area of research. In this paper characterisation of several planar dielectrics at microwave frequencies (∼9.5GHz) in the temperature range from 20 K to 290 K using a split post dielectric resonator has been presented. We have compared temperature stability of measured dielectric properties of RT5880, RT6010, LTCC, FR4 and Ba(MgTa )O materials. Presented results are useful for selection of a material suitable for a specific application. Copyright 2006 IEICE

Measurement of complex permittivity of low-temperature co-fired ceramic at cryogenic temperatures

Precise knowledge of microwave properties of Low Temperature Co-fired Ceramic LTCC materials is crucial for efficient design of microwave systems, especially for design of communication filters. Many communication devices operate at low temperatures. In order to implement LTCC at low temperature communication circuits and devices, Engineers need precise values of the complex permittivity. The aim of this paper is to characterise LTCC material as a function of temperature at microwave frequencies using a very precise measurement technique, Split Post Dielectric Resonator. The Transmission Mode Q-factor technique that eliminates all the parasitic losses during the characterisation was used for the S-parameter data processing. The permittivity and loss tangent data of LTCC manufactured by Heraeus Circuit Materials Division in the temperature range 20 K - 300K at a frequency of 9.5 GHz is reported in this paper. The random uncertainty in ε, and tanδ are better than 0.3% and 5% respectively

Microwave resonators and their use as measurement instruments and sensors

Microwave resonators of very high Q-factors, as high as 10, can currently be manufactured. In this paper an overview of different resonant structures used for measurements of dielectric properties of materials at microwave frequencies, and that can be as electromagnetic sensors of other physical quantities such as humidity, chemical reactions and level of paramagnetic impurities has been presented. Potential applications of microwave are not widely known outside the microwave community, and hence a goal of this paper is to disseminate the information to a wider engineering community