Search

In this paper we present an empirical study on the perception of the cooperative firm among entertainment and performing arts workers. In particular, the study is based on workers belonging to associations established during the first pandemic emergency from Covid-19 in 2020. Our study reveals a perception of deterioration of the cooperative model. At the same time, the participants in our research demonstrate a confidence in the ideal cooperative firm and look with interest at new cooperatives in other working sectors. The data was collected through semi-structured interviews and focus groups with cooperative and non-cooperative associated workers.

TNO has a long heritage in the research and development of radio frequency (RF) and microwave technology for phased array systems, ranging from high-level system design to hardware design, including integrated circuits and antennas. Customers include the Dutch ministries, the European Union (EU) and the European Space Agency (ESA). Innovative RF technology solutions are developed to tackle the key challenges posed by future space missions, particularly for Satellite Communication and Earth Observation. For this, TNO works in close co-operation with large space system integrators, and collaborates with other Dutch research institutes and industry. In this article a number of such developments, some performed for ESA, are presented, with recent project examples covering antenna design, Monolithic Microwave Integrated Circuit (MMIC) design and RF module design.

A fully metallic monopole element is proposed for satellite SAR antennas. This element has significant gain in the broadside direction thanks to its curved arm. This element is then studied in a large sparse array. A fast analysis technique is presented in order to solve for the currents of few hundreds elements, which correspond approximately to one millon basis functions. This method is based on macro basis functions coupled with an iterative solver accelerated with a multipole decomposion. This combination reduces drastically the memory requirements and shrinks the execution time. Good comparison between the proposed method and a commercial software solution is provided. © 2019 European Association on Antennas and Propagation.

A novel sparse layout for the receiving aperture of a Ka-band spaceborne SAR has been designed. The devised array antenna layout allows reducing the number of active controls of 40%, from 10000 to 6000. The antenna is designed to steer the beam ±10° in elevation and ±2° in azimuth, and satisfies the prescribed pattern mask. In this paper, after briefly recalling the electromagnetic design of the antenna, the arrangement of the electronic layeris described in detail, together with the thermomechanical design and the aspects concerning the accommodation of this sparse SAR array antenna in the satellite bus.

In this contribution, a dielectric dome antenna design in Ka-band is presented. The dome antenna is based on the combination of a phased array and a dielectric lens. The goal of the combination of these structures is to enlarge the field of view of the antenna. In particular, the array is considered to be able to scan up to 60º and the lens is used to enhance the field of view up to 80º. To this end, the optimization variables of the antenna are the shape of the dielectric lens, its thickness, its dielectric constant and the phase distribution over the array. The optimization procedure is based on a ray-tracing technique. In order to quantify the performance of the dome antenna, a physical optics code was developed to calculate the radiation patterns. The results show good quality patterns over the considered scanning range. The dielectric dome solution is not frequency dependent, and therefore, the bandwidth of the antenna will only be limited by the phased array.

This paper presents a novel ultra wide band (UWB) leaky slot antenna. The antenna has a wide impedance bandwidth from 3 to 14 GHz and it is suitable for radar applications requiring high resolution, phase center stability and good pulse preservation, such as medical imaging and ground penetrating radar. © 2013 EurAAP.

The Cornell University Life Sciences Core Laboratories Center (CLC) provides an array of genomics, proteomics, imaging and informatics shared research resources and services to the university community and to outside investigators. The CLC includes fee-for-service research, technology testing and development, and educational components. The Center has seven core facilities, including genomics (DNA sequencing, genotyping, and microarrays), epigenomics, proteomics and mass spectrometry, microscopy and imaging, bioinformatics, bio-IT, and advanced technology assessment. The CLC is part of a New York State designated Center for Advanced Technology in Life Science Enterprise. The mission of the CLC is to promote research in the life sciences with advanced technologies in a shared resource environment. Use of the CLC resources and services is steadily increasing due to the growth in the number and types of cores in the center, to the expansion of existing services and the implementation of new core technologies, and to the coordinated integration and synergy of services between the CLC cores. Multidisciplinary support for multi-functional instrument platforms is implemented by integrated operations of the CLC core facilities. Investigators are offered coordinated project consultations with the directors and staff of all relevant cores during the design, data production and analysis phases of their projects. The CLC is involved in establishing and supporting multidisciplinary research projects that involve both intercampus initiatives and multi-institutional collaborations. With a concentration of advanced instrumentation and expertise in their applications, the CLC is a key resource for life sciences research.

CF-13

The protection of phased array T/R modules from high input power levels is an important aspect in reducing vulnerability of radars and communication systems RF electronics in modern military platforms. Different categories of threats can damage the sensitive electronics in the phased-array radar, like hostile high power electro-magnetic (HPEM) pulses or the radar’s own transmitted signal. In this paper, a novel approach to this problem is proposed, which consists of distributing the protection at different levels of the T/R module instead of confining it to a single device, as it is currently done in most existing systems. Enabling technologies for this solution are briefly described and several examples of protection architectures developed at TNO are presented

This paper presents some of the results of the measurement campaign that was undertaken in order to validate some of the properties that had been previously anticipated for the enhanced leaky lens antenna. To our knowledge the link between two leaky lenses is demonstrated to be less dispersive than any other radiation link previously reported .

This paper provides a comparison between two different techniques for the array pattern side-lobe reduction in a passive radar system based on a circular array. The first method retrieves the phase modes pattern for the reference array and then applies a conventional tapering for the side lobe suppression of the obtained virtual uniform linear array. The second approach foresees instead an optimization algorithm in order to obtain the desired level of the side lobes. Both techniques have been adapted for being used with an 8 elements FM-based circular array for passive radar applications developed at TNO - Defence, Security and Safety in The Hague. The effect of the directional elements has been also considered for the array pattern synthesis. The different advantages of the algorithms are described and a distinction about the possible fields of application is retrieved. © 2010 EuMA.

European CH4 emissions are estimated for the period 2001-2006 using a four-dimensional variational (4DVAR) inverse modeling system, based on the atmospheric zoom model TM5. Continuous observations are used from various European monitoring stations, complemented by European and global flask samples from the NOAA/ESRL network. The available observations mainly provide information on the emissions from northwest Europe (NWE), including the UK, Ireland, the BENELUX countries, France and Germany. The inverse modeling estimates for the total anthropogenic emissions from NWE are 21% higher compared to the EDGARv4.0 emission inventory and 40% higher than values reported to U.N. Framework Convention on Climate Change. Assuming overall uncertainties on the order of 30% for both bottom-up and top-down estimates, all three estimates can be still considered to be consistent with each other. However, the uncertainties in the uncertainty estimates prevent us from verifying (or falsifying) the bottom-up inventories in a strict sense. Sensitivity studies show some dependence of the derived spatial emission patterns on the set of atmospheric monitoring stations used, but the total emissions for the NWE countries appear to be relatively robust. While the standard inversions include a priori information on the spatial and temporal emission patterns from bottom-up inventories, a further sensitivity inversion without this a priori information results in very similar NWE country totals, demonstrating that the available observations provide significant constraints on the emissions from the NWE countries independent from bottom-up inventories. © Copyright 2010 by the American Geophysical Union

In this paper the concept of limiting frequency selective surface (FSS) is presented. The design of a reconfigurable FSS equipped with PIN diodes, aimed at the protection of a radar receiver from high power impinging electromagnetic waves is outlined and verified against the measurement results of a hardware demonstrator.

In this paper, we introduce a general framework to efficiently optimize phased array antennas integrated with frequency selective surfaces (FSS) and feeding elements. The framework consists of two main parts: the first being parametric models that enable fast evaluation of the full-wave problem for a range of frequency, scan angle and geometry parameters. The second part consists of a number of optimization methods to generate an optimum set of geometry parameters by minimization of a penalty function. Results are shown for parametric models and the optimization of various examples.

Frequency Selective Surfaces (FSS's) are periodic arrays of patches and/or slots etched on a metal plate, having frequency and angular ??ltering properties. The FSS response to an excitation (for example a plane wave) is characterized in terms of its re ection and transmission coe??cient, and depends on the element type (slot or patch), the element shape (loop, cross, ...) and the array grid (rectangular or triangular). Cascading a number of FSS's to each other allows achieving larger bandwidths and steeper roll o??s. The angle dependence of the response can be reduced by sandwiching the FSS's between dielectric slabs. As a special application, the (multi-layer) selective structure is integrated with an array antenna: for example to reduce the antenna's radar cross section or to obtain wideband/multi-frequency antennas. The analysis and the design of a multi-layer FSS, possibly integrated with an antenna, requires the availability of a CAD package based on an e??cient analysis methodology. In this respect, microwave network techniques constitute an appropriate choice because of their modularity. Originally introduced for the analysis of waveguides, they have been extended to periodic structures. The basic idea is to derive a representation of layers and transitions between adjacent layers in terms of equivalent networks. The entire structure is then represented by the cascade of these networks. Di??erent choices of parameters to characterize the structure lead to di??erent types of equivalent network: for example, scattering parameters are used to derive the generalized scattering matrix. The adjective 'generalized' refers to the fact that the input and output ports correspond not only to the propagating modes but also to the evanescent ones. In the conventional approaches, the number of these ports is equal to the number of modes used to represent the electromagnetic ??eld at the transition. From this general equivalent network, a reduced form can be derived, which includes only the modes that actually contribute to the electromagnetic interaction between two successive transitions (accessible modes). If the structure consists of many layers, this reduced form is convenient to limit the calculation time, and it is necessary for some types of network representations to avoid the instability problem that arises when many networks are cascaded to each other. The distinguishing feature of the Integral Equation method for the derivation of Multimode Equivalent Networks (IEMEN), described in detail in this thesis, is that it resorts directly to an equivalent network representation in terms of the accessible modes only. The innovative idea is to retain as accessible, in the analysis of a certain transition, only those evanescent modes that arrive at the terminal planes with an attenuation factor that is smaller than a chosen maximum tolerance. The corresponding modal amplitudes are then identi??ed as the fundamental unknowns of the problem, in the sense that all the ??elds in the region between the terminal planes can be expressed as a linear combination of those quantities only. This results in the formulation of the scattering problem in terms of a single integral equation with reduced kernel, and corresponding reduced Green's function, and multiple forcing terms, one for each accessible mode. The formulation has been extended to e??ciently analyze structures containing thin layers, as for example bond ??lms. The IEMEN method has been implemented in a software tool and its analysis capabilities have been demonstrated for some representative examples presented in literature, and by comparing with analysis results obtained by means of commercial software. The tool is also a reliable and exible instrument for the design and it has been successfully used to solve a realistic design problem, consisting of an FSS to be integrated with a waveguide phased array. The FSS had to prevent interference between the array and a satellite communication antenna, located in its proximity. A dipole-based FSS was identi??ed as suitable geometry to meet the requirements. A classical design procedure has been adopted. It starts with a single-mode design, intuitive and Smith-chart based, to trace the relevant behavior of the structure and to perform a rough tuning of the FSS parameters. With respect to the transmission line corresponding to the main propagating Floquet mode, the FSS was characterized by a simple shunt equivalent admittance. The actual value of this admittance, as a function of the frequency, was obtained by means of the IEMEN approach. This initial design phase was followed by a re??nement phase, in which full-wave IEMENbased simulations, including all the relevant accessible modes, were used. It should be noted that, since the patch admittance is a slowly varying function of the frequency, it can be linearly approximated near the resonance. As a consequence, the ??rst design phase was very fast. This property holds also for the elements of the equivalent admittance matrix of a patch FSS, when a larger number of accessible modes is retained in the calculations, and it is a characterizing feature of the IEMEN method. In fact, all the fast frequence variations are accounted for at transmission-line level and not at equivalent-network level, because the modes that vary most rapidly with the frequency have been extracted from the IE kernel. The designed FSS has been manufactured and measured using di??erent setups. Subsequently, the properties of the reduced kernel integral equation have been investigated for an expansion of the unknown current by means of sub-domain basis functions. To comply with very stringent requirements set on the FSS, in terms of incidence angles and roll o??, dielectric slabs with high permittivity are required. As a consequence, the number of accessible modes to be included in the simulations increases and, for a sub-domain expansion of the unknown currents, the Method of Moments (MoM) matrix becomes ill conditioned. In particular, we have considered a simple two-dimensional geometry, consisting of an in??nite periodic array of metallic strips in free space under TM plane wave incidence. An asymptotic expression of the non-accessible Green's function has been derived where, besides the typical singularity, an oscillating term can be recognized. The amplitude of this term depends on the number of accessible modes extracted from the complete kernel and the period is the same as that of the Floquet waves with index equal to the index of the highest-order accessible mode. From a parametric study, it is observed that, if sub-domain functions are used to expand the unknowns, the MoM matrix condition number increases with the number of accessible modes and with the strip width. The intuitive explanation is that the natural modes of the array resonate with the Floquet modes. The study of the eigenvalue equation associated to the reduced IE operator has con??rmed this hypothesis. In fact, its eigenfunctions appear to be similar to combinations of the extracted Floquet waves. Consequently, the solution can be represented as a combination of Floquet modes. This con??nes the solution to a subspace of the solution space where the small unwanted eigenvalues are avoided. Thus, using a limited number of global basis functions can be seen as a way of regularizing an ill-conditioned problem. In particular, we have selected truncated Floquet waves (tfw), variations of those proposed in literature as entire domain basis functions for the analysis of large ??nite slot arrays. Furthermore, the particular formulation of the IEMEN approach, with a single IE and di??erent forcing terms, suggests the adoption, for each speci??c forcing term, of a di??erent compact set of tfw's, which can be used to solve the integral equation. This implies that a di??erent matrix has to be inverted for each accessible mode. Since only a few basis functions are needed to solve the problem corresponding to a given forcing term, the computational time is related to the calculation of the MoM matrix elements, rather than to the matrix inversion. Therefore, the e??ciency of the method of solution is not compromised. A number of test cases has been presented, demonstrating the advantage of using tfw's as basis functions instead of sub-domain functions, as well as a discussion on the nature of the eigenvalues of the reduced kernel IE.

The Multimode Equivalent Network approach based on the Integral Equation formulation (IEMEN), originally proposed for waveguide structures, has been extended in [1] to the analysis of multi-layer FSS's. This method formalizes the scattering problem in terms of a single integral equation with reduced kernel and corresponding reduced (non-accessible) Green's Function, by directly exploiting the concept of accessible modes. In this contribution we investigate the reduced kernel behavior for a simple 2D geometry, consisting of an infinite periodic array of metallic strips in free-space under TM plane wave incidence.

This paper describes an efficient methodology for the design of steep roll-off Frequency Selective Surfaces (FSS’s). The proposed technique is based on the Multimode Equivalent Network (MEN) approach, which was originally developed for the analysis of waveguide junctions. The MEN has been extended to the study of multi-layer patch based and aperture based FSS’s. The result is a general formulation that allows characterizing complex structures, consisting of radiating apertures and FSS’s, in the same framework used to account for feeding and filtering elements inside the waveguides. Moreover, thanks to the modularity of this approach, it will be shown in the paper that it can be used as agile design tool. In particular, this paper describes the design procedure for a multi-layer FSS to be integrated with the X-band phased array of a Multi Functional Radar (MFR) in order to prevent interference from an antenna located in its proximity and operating in a partially overlapping frequency range. The analysis results of this integrated structure, obtained with our tools, were compared with those produced by a commercial code, showing very good agreements. The designed FSS has been manufactured and measured for different incidence angles.

The use of Frequency Selective Surfaces (FSS) is becoming more and more frequent in the design of antennas for complex warship platforms. From the antenna point of view, the main challenge is the capability of designing antennas with high performances, integrated in complex platforms with low Radar Cross Section (RCS) and a high number of different antenna systems mounted on the same support. This clearly requires the capability of improving the frequency and angular selectivity of the antenna, keeping at the same time under control the dimensions and shapes of the antenna itself. The solution to these requirements is the design of array antennas integrated with FSS panels with different frequency/angular filtering behavior. In previous works, we have already presented an efficient and flexible approach to this kind of problem based on a Multi-mode Equivalent Network (MEN) method (G. Gerini, L. Zappelli, Conference Proceedings 31st European Microwave Conference, 2001, pp. 321-324), (S. Monni, G. Gerini, A. Neto, XXVII URSI General Assembly, 2002). This technique allows the derivation of an accurate multi-mode impedance matrix representation of the overall structure including array, arbitrary shaped FSS’s and radomes placed on the top of the array itself. A crucial aspect in terms of accuracy and efficiency is the choice of the expanding functions for the unknown electromagnetic quantities. Hence, in order to investigate this aspect, in this contribution we analyze the effects of expanding the unknown electromagnetic quantities in terms of different basis. We have considered both piecewise sinusoidal expanding functions and full-domain modal representations obtained by the BCMM (boundary contour mode matching) method (F. Giese, J. M. Reiter, F. Arndt, IEEE MTT'S Digest, 1995, pp. 1359-1362). These different expansions have been applied to dual problems like metallic patches and screens of infinitesimal thickness and arbitrary cross-section. In general, piece-wise sinusoidal functions have a very simple analytical form and offer a great flexibility in terms of shapes that can be analyzed. On the other end, their large spectral content is such that a very large number of terms (proportional to the scalar product of the expanding functions with the Floquet’s modes) have to be summed up in the kernel of the integral equation. This would lead to a relatively large CPU time, unless efficient acceleration techniques are applied in the summation of the series. On the contrary, full domain basis functions are less flexible for the analysis of complex shapes and often require the solution of an eigenvalue problem for the eigenmodes determination. Nevertheless, a relatively smaller number of functions are necessary to describe the unknown fields in complex geometries and furthermore their spectral content is such that the kernel of the IE is more rapidly converging. A comparison between results for the same problem obtained with the two expansion sets will be presented at the conference, together with a detailed trade-off study in terms of accuracy and computing time.

This contribution presents the evolution of the work on Frequency Selective Surfaces (FSS) that is being performed at TNO-FEL. In particular the extension of the previously developed Multimode Equivalent Network approach to cope with patch based structures is presented. In order to derive the network, first a set of reduced kernel integral equations that enforce the null of the tangent electric field (EFIE) on the metal surfaces are introduced. Their formal solution is then used to obtain the Z matrix that characterizes the junction in a multimode network representation. The obtained z-matrix can then be connected to the already existing software code that consents to characterize generic wave-guide geometries connected with aperture based FSS’s