Substrate integrated waveguides (SIW) maintain the advantages of planar circuits (low loss, low profile, easy manufacturing, integration in a planar circuit board), and improve quality factor of filter resonators. Empty substrate integrated waveguides substantially reduce the insertion losses because waves propagate through air instead of through a lossy dielectric. The first empty substrate integrated waveguide (ESIW) used a simple tapering transition that can not be used for thin substrates. A new transition has recently been proposed which includes a taper also in the microstrip line, not only inside the ESIW, and so it can be used for all substrates, although measured return losses are only 13 dB. In this work the cited transition is improved by placing via holes that prevent undesired radiation, as well as two holes that help to ensure good accuracy in the mechanization of the input iris, thus allowing very good return losses (over 20 dB) in the measured results. A design procedure, that allows the successful design of the proposed new transition, is also provided. A back to back configuration of the improved new transition has been successfully manufactured and measured.

SummaryThe concept of eco-efficiency can be defined by using the "product value/environmental influence" ratio. Different models have been proposed to measure eco-efficiency. The main difference among them is the weighting system used to aggregate the environmental results. Data Envelopment Analysis (DEA) permits this aggregation without requiring a subjective judgment about the weights. In this study, a DEA model was applied to Spanish Mahón-Menorca cheese production to determine the most eco-efficient production techniques.To this end, 16 scenarios of Mahón-Menorca cheese production were built regarding technical (degree of automation) and cleaner production criteria. The environmental impacts were assessed by means of the Life Cycle Assessment. An economic assessment was carried out by determining the economic value added and the net income for each scenario. The results are referred to as 1 kg cheese ripened over 105 days.By using DEA, an eco-efficiency ratio lying between 0 and 1 was obtained. Three scenarios were found to be eco-efficient, using a high degree of automation (enclosed vat and molding and demolding machines) and accelerated cheese ripening.The Montecarlo simulation was used to carry out a sensitivity analysis to compare the influence of price changes on the eco-efficiency ratio. The results emphasized the consistency and stability of the eco-efficient scenarios. IntroductionAccording to the results from a study financed by the European Union (EU), one of the product groups with the highest environmental impact throughout its entire life cycle is foods, especially dairy and meat products (Tukker et al. 2006). For this reason, food production systems need to be rethought in order to be more environmentally friendly.The food industry is one of the main contributors to discovering new solutions and, therefore is highly relevant. In this context the role of cleaner production techniques must be emphasized since they have a pro-active focus instead of a reactive one. They have the potential to reduce emissions and waste produced in the production process and, consequently waste treatment. Nevertheless, establishing the best available techniques requires that not only the environmental aspects, but also the economical ones, be taken into account. The eco-efficiency concept embraces these two aspects.Eco-efficiency of production concerns the capability to produce goods and services while causing minimal environmental degradation. According to World Business Council for Sustainable development (WBCSD 2000), eco-efficiency is represented by the ratio "Product or service value/Environmental influence". Kuosmanen and Kortelainen (2005) consider the eco-efficiency concept to be critically important for at least two reasons: (1) it is often the most effective way of reducing environmental pressures; (2) policies targeted at efficiency improvements tend to be easier to adopt than policies that restrict the level of economic activity. The ecoefficiency concept and the search for eco-efficie...

The paper presents a new accurate and efficient technique for the analysis of H-plane single or multiple rods in rectangular waveguides. The new method is based on a mode matching procedure that matches open space and guided modes along a circular boundary that encloses the rods. Since the EM fields around the obstacles are expanded using open space cylindrical modes, a full analytical (and highly efficient) solution can be obtained for dielectric or metallic circular posts. However, this technique can also cope with any arbitrary geometry of the H plane obstacles. In such a case, a numerical method should be used to characterize geometries other than circular in terms of cylindrical modes, and therefore the efficiency would be reduced.The method has been successfully applied to the analysis and design of several H plane filters with different topologies involving single centered and off-centered posts, as well as double post geometries.

There are several practical applications in microwave engineering that require the cascade connection of multiple twoport scattering matrices. Many microwave devices are analyzed by segmenting the structure into small building blocks (steps, resonators, lines, etc.) that are characterized by means of the generalized scattering matrix. In order to obtain the reflection and transmission parameters of the entire structure, the scattering matrices of all the building blocks must be cascaded. Traditionally, the conversion of the scattering matrices to or matrices has been used in order to perform the cascade connection. An alternative to this procedure is to perform a recursive connection by pairs of the scattering matrices. In this paper, we present a new technique for the efficient cascade connection of monomodal or multimodal scattering matrices that reduces the computation time by 35% when compared to the cascading by pairs, and by 75% when compared with the use of matrices.

A new hybrid mode matching and method of moments formulation based only on electric currents is presented in this paper. The use of only one equivalent current allows the introduction of a new set of unknowns. The chosen new unknowns are the weights related to the scattered modes that emerge from the ports to the waveguides that feed the problem. Applying this new formulation, the matrices that must be inverted are smaller and the generalized scattering matrix can be obtained directly from the solution of the resulting system of equations, so that no additional projection is needed to obtain the scattering parameters, as happens with traditional approaches with two equivalent currents. As a result, certain efficiency improvement is obtained, as can be seen when this technique is applied to the solution of H plane problems in rectangular waveguide.