@conference {13_URSIUSA_Leal-SevillanoRuiz-CruzMontejo-GaraiEtAl_EquivalentcircuitofMultiaperture, title = {Equivalent circuit of multi-aperture waveguide irises and its application in the design of compact filters}, booktitle = {Proc. 2013 USNC/URSI National Radio Science Meeting}, year = {2013}, month = {July}, pages = {11}, abstract = {Equivalent circuits of waveguide discontinuities and volumes were use in the past for the design of microwave devices, N Marcuvitz, "Waveguide Handbook". Nowadays, most of this waveguide structures can be analyzed and optimized using rigorous full-wave methods (either numerical or quasi-analytical) with acceptable computation times. Nevertheless, an accurate equivalent circuit provides physical insight of the structure. This additional electromagnetic knowledge might lead to the design of new high-performance waveguide components. Moreover, non-ideal behaviors commonly obtained in experimental measurements, such as narrow band spike resonances, can be explained by means of accurate equivalent circuits. This work is divided in two parts: first an accurate and wide-band equivalent circuit of multi-aperture waveguide irises is determined; then this equivalent circuit is applied in the synthesis of compact waveguide filters, including pseudo-elliptical band-pass, dual band and stop-band filters. The proposed equivalent circuit of multi-aperture irises (with an arbitrary number of apertures) is based on an in deep electromagnetic analysis of the possible resonances of these structures. Two different kind of resonances are possible, either implementing a refection zero (resonances) or a transmission zero (antiresonances). The equivalent circuit is a parallel admittance with a circuit topology given by any of the classical one-port LC realizations, G C Temes and J. W. LaPatra, "Introduction to Circuit Synthesis and Design". The values of the circuit elements are entirely determined by the singular points (resonances and antiresonances) obtained in the full-wave analysis. Modeling of different multi-aperture waveguide irises by means of the proposed equivalent circuit, including experimental results of a five apertures iris, will be addressed in the presentation. Some designs of waveguide filters using the particular case of two-fold symmetric irises with three apertures will be presented. The design discussion will be focused on a systematic synthesis method based on the accurate modeling of the waveguide irises.}, author = {C A Leal-Sevillano and J A Ruiz-Cruz and Montejo-Garai, J R and J A Ruiz-Cruz and Rebollar, J M} } @conference {13_URSIESP_Mecia-OlivaGrajal-de-la-FuenteBadolatoEtAl_Experimentalradarimager300GHz, title = {Experimental radar imager with sub-cm range resolution at 300 GHz}, booktitle = {Proc. 2013 Simposium Nacional URSI (in Spanish)}, year = {2013}, month = {Sept.}, pages = {1-7}, abstract = {This paper presents a high range resolution radar sensor working in the submillimeter-wave band for standoff detection and security applications. Low-cost technologies have been properly selected in order to implement a versatile and easily scalable radar system. A large operational bandwidth, required for high range resolution, is attained by means of a frequency multiplication-based architecture. This radar system sweeps a bandwidth of 27 GHz. The final application allows the generation of 3D images by means of the radar front-end integrated with a bifocal ellipsoidal Gregorian reflector system. The scene of interest is elliptically scanned at a standoff range of 8 m. In addition, some of the design and fabrication techniques of components at the millimeter and submillimeter-wave bands are presented.}, author = {Mecia-Oliva, B and Grajal-de-la-Fuente, J and Badolato, A and Garcia-Pino, A and Besada-Sanmartin, J L and C A Leal-Sevillano and J A Ruiz-Cruz and Montejo-Garai, J R and Rebollar, J M} } @article {10_ELMG_Montejo-GaraiRuiz-CruzRebollar_EfficientOMUXSingleTerminated, title = {Efficient Design of Contiguous-Band Elliptic-Response Manifold Output Multiplexers with Single-Terminated Filters}, journal = {Electromagnetics}, volume = {30}, number = {8}, year = {2010}, note = {falta pos en JCR de su a{\~n}o}, month = {November}, pages = {644-659}, abstract = {A procedure for the synthesis and design of contiguous-band manifold output multiplexers based on singly terminated filters with an elliptic response is presented. An extension of the Cauer ladder development using the zero-shifting technique leads to the synthesis of a driving-point impedance, including transmission zeros at finite real frequencies. The synthesized canonical forms have different topologies, number of reactive constant elements, and reactive part of the driving impedance, which have been compared to find the most suitable combination in the multiplexing process to match the channels to the manifold. The study proposed here is very important for improving the design process, and it is illustrated with four different multiplexer configurations and implemented with different pole-extraction orders in the ladder singly terminated filters. The multiplexer design has been divided into tasks with low computational effort extensively using the circuit model. Thus, the final full-wave optimization is significantly reduced, since the starting point is closer to the required specification. Finally, a Ku-band four-channel elliptic-response multiplexer has been designed in the H-plane rectangular waveguide, manufactured and measured in order to show the proposed approach.}, keywords = {H-plane, mode matching, transmission zero}, issn = {0272-6343}, doi = {10.1080/02726343.2010.524879}, url = {http://www.informaworld.com/smpp/content~db=all?content=10.1080/02726343.2010.524879}, author = {Montejo-Garai, J R and J A Ruiz-Cruz and Rebollar, J M} } @article {09_APL_Medina-MenaRuiz-CruzMesa-LedesmaEtAl_ExpEOTNoPlasmons, title = {Experimental verification of extraordinary transmission without surface plasmons}, journal = {Applied Physics Letters}, volume = {95}, number = {7}, year = {2009}, month = {August}, pages = {1-3}, abstract = {This letter provides an experimental demonstration of extraordinary transmission in a closed waveguide system loaded with an electrically small diaphragm. This is a situation where the standard surface plasmon polariton (SPP) theory does not apply. The theoretical explanation is then based on the concept of impedance matching. This concept has previously been applied by some of the authors to account for enhanced transmission in situations where surface plasmon theory can be used: periodic arrays of small holes or slits in flat metal screens. The experiment in this letter supports the impedance matching model, valid for when SPPs are present or not}, keywords = {impedance matching, light transmission, optical waveguides, periodic structures, polaritons, surface electromagnetic waves, surface plasmons}, issn = {0003-6951}, doi = {10.1063/1.3206738}, url = {http://apl.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf\&id=APPLAB000095000007071102000001\&idtype=cvips}, author = {Medina-Mena, F and J A Ruiz-Cruz and Mesa-Ledesma, F and Montejo-Garai, J R and Rebollar, J M and Marques-Sillero, R} }