Peter Barnwell

A simple method for accurate loss tangent measurement of dielectrics using a microwave resonant cavity

A simple yet rigorous method has been developed to enable the loss tangent of dielectrics, having a known relative permittivity, to be accurately measured using a waveguide resonant cavity. The novel method eliminates the need for any physical measurement, either on the cavity or dielectric sample under test. The only electrical parameters that need to be measured are resonant frequencies and Q-factors of a reference cavity and those of the same cavity loaded with the dielectric sample. One of the advantages of the new technique is that dielectrics, of arbitrary shape, can be characterized at very high microwave frequencies. The new method has been verified through measurement over X-band.

Design of directional couplers using multilayer thick-film technology

The performance of multilayer directional couplers using a range of different thick-film dielectrics has been investigated. The properties of multilayer coupled lines are examined using their coupled-mode parameters. It is found that the optimum performance of multilayer directional couplers is largely affected by the thick-film dielectric used. A practical design strategy for multilayer directional couplers is developed, which overcomes the problem of excessive computation that is normally associated with the optimization of multilayer circuit designs. The methodology has been verified through the design and measurement of wide bandwidth 2 dB and 3 dB directional couplers that were fabricated using multilayer thick-film technology.

Multi‐layer thick‐film microwave components and measurements

The trend in wireless and mobile communications for broader bandwidth microwave circuitry, coupled with high packaging density and low cost fabrication has triggered investigations of new circuit configurations and technologies that meet these requirements. We have addressed these issues through the study of multilayer microwave structures using advanced thick‐film technology. The techniques described employ several layers of metal sandwiched by thick‐film dielectric. This leads to an efficient solution for system miniaturisation. The significance of this work is that it shows the multilayer approach to microwave structures, coupled with new thick‐film technology, offers a viable and economic solution to achieve high‐density, high‐performance microwave circuits.

Substrate characterization: simulation and measurement at high microwave frequencies

In this paper we present new measured loss tangent data for commercially available substrates, and these data are supported by simulations that show how practical variations in loss tangent affect the performance of microwave interconnections and devices. The paper reviews the measurement techniques that are currently available to measure the dielectric constant and loss tangent of substrate materials, and includes a new variation on an existing method that enables substrate parameters to be more easily measured but retains high accuracy. Simulations have been performed on microstrip lines fabricated on 10mil thick substrates using gold conductors to show the relative contributions of conductor and dielectric loss to the total line loss over the frequency range 0‐40GHz. Included in these simulations are the effects of conductor surface roughness. The simulated data are related to measured line microstrip line loss data over the frequency range 50MHz‐40GHz. The measured values, for an etched gold line on alumina, vary from 0.0045dB/mm at 50MHz to 0.04dB/mm at 40GHz.

European Microelectronics Conference '87

The conference and exhibition got off to a good start with an official reception by the Mayor of Bournemouth on Tuesday evening where attendees could relax and chat—a pleasant way to meet old friends and to make new acquaintances.