@conference {15_CNM_Polo_hornmodematching, title = {Analysis and design of horn antennas with arbitrary profile using mode-matching}, booktitle = {Congress on Numerical Methods in Engineering, CMN 2015}, year = {2015}, month = {July}, author = {L Polo-Lopez and J A Ruiz-Cruz and J C{\'o}rcoles and C A Leal-Sevillano} } @conference {15_URSI_JORGE_INVITADA, title = {Desarrollo de componentes pasivos con divisi{\'o}n/combinaci{\'o}n de potencia para sistemas de comunicaciones}, booktitle = {Simposium Nacional URSI 2015}, year = {2015}, month = {September}, abstract = {This paper addresses the development of passive devices for communication systems working at the microwave frequency band, but also at millimeter-wave and terahertz frequencies. A brief review of different types of passive devices that the authors have been developed for different applications will be made. The paper will be focused on the devices for the last stage of the transmitter/receiver chain in communications systems, where the antennas and other components such as filters, multiplexers, polarizers, dividers/combiners, etc are an essential part. The application of these devices to power combination techniques will be also outlined, which can be used in high-power amplification, but also in other problems as antenna arrays.}, author = {B Taha-Ahmed and J C{\'o}rcoles-Ortega and R V Haro-Baez and C A Leal-Sevillano and J L Masa-Campos and J R Montejo-Garai and E Garcia-Marin and A Mor{\'a}n-L{\'o}pez and L Polo-Lopez and J M Rebollar-Machain and J A Ruiz-Cruz and P Sanchez-Olivares} } @article {14_IEEETMTT_Leal-SevillanoYingaTaoLancasterEtAl_MicromachinedDual-BandOrthomode, title = {A Micromachined Dual-Band Orthomode Transducer}, journal = {IEEE Transactions on Microwave Theory and Techniques}, volume = {62}, number = {1}, year = {2014}, month = {January}, pages = {55-63}, abstract = {In this paper, an orthomode transducer (OMT) for dual-band operation and optimized for stacked micromachined layers implementation is presented. The proposed design avoids the use of septums, irises, pins, or small features and minimizes the number of equal-thickness micromachined layers required. In this way, the micromachining fabrication is simplified, making the proposed design a very attractive candidate for high frequency applications and for low-cost batch production. A W-band dual-band design (one different polarization in each frequency band) with more than 10\% fractional bandwidth for each band and 30\% separation between bands is presented. In addition, proper routing and layered bends are designed for an optimum standard interfacing with the same orientation of the input/output ports. Two OMTs in a back-to-back configuration are fabricated using a thick SU-8 photo-resist micromachining process. A total of six stacked SU-8 layers, all of them with the same thickness of 635 micrometers, are used. The experimental results are coherent with the tolerance and misalignment of the process, validating the proposed novel OMT design.}, issn = {0018-9480}, doi = {10.1109/TMTT.2013.2292611}, url = {http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6678791}, author = {C A Leal-Sevillano and YingaTao, T and Lancaster, M J and J A Ruiz-Cruz and Montejo-Garai, J R and Rebollar, J M} } @conference {14_EuCAP_Leal-SevillanoRuiz-CruzMontejo-GaraiEtAl_NovelDual-BandSingle, title = {Novel Dual-Band Single Circular Polarization Antenna Feeding Network for Satellite Communications}, booktitle = {Proc. 2014 European Conference on Antennas and Propagation (EuCap)}, year = {2014}, month = {Apr.}, pages = {1-5}, abstract = {In this paper a novel dual-band single circular polarization antenna feeding network for satellite communications is presented. The novel antenna feed chain1 is composed of two elements or subsystems, namely a diplexer and a bi-phase polarizer. In comparison with the classic topology based on an orthomode transducer and a dual-band polarizer, the proposed feed chain presents several advantages, such as compactness, modular design of the different components, broadband operation and versatility in the subsystems interconnection. The design procedure of this new antenna feed configuration is explained. Different examples of antenna feeding networks at 20/30 GHz are presented. It is pointed out the excellent results obtained in terms of isolation and axial ratio.}, keywords = {antenna, Circular polarization, diplexer, dual-band, K/Ka band, multibeam, orthomode transducer, polarizer, satellite communications, waveguide}, author = {C A Leal-Sevillano and J A Ruiz-Cruz and Montejo-Garai, J R and Rebollar, J M} } @article {13_IEEETHz_Leal-SevillanoCooperRuiz-CruzEtAl_225GHzCircularPolDuplexer, title = {A 225 GHz Circular Polarization Waveguide Duplexer Based on a Septum Orthomode Transducer Polarizer}, journal = {IEEE Transactions on Terahertz Science and Technology}, volume = {3}, number = {5}, year = {2013}, month = {Sep.}, pages = {574-583}, abstract = {In this paper, we present the modeling and experimental validation of an efficient, compact, and high-isolation waveguide duplexer operating at 225 GHz. While duplexers based on ferrite circulators are key components of many monostatic radar systems, at W-band frequencies and above the performance of waveguide circulators rapidly deteriorates. The design presented here uses a ferrite-free duplexing concept based on transmitting and receiving in orthogonal circular polarizations. The circular polarization is efficiently generated in waveguide using a septum orthomode transducer polarizer, leading to a compact device with a single horn antenna. The complete duplexer is designed using efficient numerical algorithms, resulting in a fabricated device with a measured 10\% fractional bandwidth, a return loss better than 20 dB, isolation of 30 dB, and insertion loss below 1 dB.}, keywords = {Circular polarization, duplexer, orthomode transducer, terahertz}, issn = {2156-342X}, doi = {10.1109/TTHZ.2013.2264317}, url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=\&arnumber=6525512}, author = {C A Leal-Sevillano and Cooper, K B and J A Ruiz-Cruz and Montejo-Garai, J R and Rebollar, J M} } @conference {13_EuMC_Leal-SevillanoRuiz-CruzMontejo-GaraiEtAl_CompactBroadbandCouplersMagicT, title = {Compact Broadband Couplers Based on the Waveguide Magic-T Junction}, booktitle = {Proc. 43rd European Microwave Conference}, year = {2013}, issn = {978-1-61284-235-6}, author = {C A Leal-Sevillano and J A Ruiz-Cruz and Montejo-Garai, J R and Rebollar, J M} } @conference {13_CSTUGM_Montejo-GaraiRuiz-CruzLeal-SevillanoEtAl_DesignofDual-PolarizationDiplexers, title = {Design of Dual-Polarization Diplexers Based on Enhanced Turnstile Junctions}, booktitle = {2013 CST European User Group Meetings}, year = {2013}, month = {May}, author = {Montejo-Garai, J R and J A Ruiz-Cruz and C A Leal-Sevillano and Rebollar, J M} } @conference {13_Montejo-GaraiRuiz-CruzLeal-SevillanoEtAl_DesignofDual-PolarizationwithFreqDsicrimi, title = {Design of Dual-Polarization Waveguide Devices with Frequency Discrimination}, booktitle = {2013 IEEE MTT-S International Microwave Symposium Digest}, year = {2013}, month = {June}, pages = {1-4}, abstract = {The goal of this workshop is to introduce the main topologies for devices handling both the frequency discrimination and dual-polarization at the same time. The particular issues that have to be taken into account when addressing the dual-polarization operation along with frequency discrimination in waveguide components will be studied. Antenna feeders with simultaneous linear or circular polarization working at frequency bands with very large separation will be discussed.}, author = {Montejo-Garai, J R and J A Ruiz-Cruz and C A Leal-Sevillano and Rebollar, J M} } @conference {13_EuMC_Leal-SevillanoRuiz-CruzMontejo-GaraiEtAl_Dual-BandBi-PhasePolarizerNonOMT, title = {Dual-Band Bi-Phase Waveguide Polarizer for a Novel Feeder Network without Orthomode Transducer}, booktitle = {Proc. 43rd European Microwave Conference}, year = {2013}, issn = {978-1-61284-235-6}, author = {C A Leal-Sevillano and J A Ruiz-Cruz and Montejo-Garai, J R and Rebollar, J M} } @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} } @article {13_JEMWA_Leal-SevillanoMontejo-GaraiRuiz-CruzEtAl_ExperimentalcomparisonofWBandFilters, title = {Experimental comparison of waveguide filters at W-band implemented by different machining processes and split-block}, journal = {Journal of Electromagnetic Waves and Applications}, volume = {27}, number = {18}, year = {2013}, month = {Oct}, pages = {2390-2394}, abstract = {The aim of this work is to explore different machining processes and different split-block, getting important experimental information for the design of passive waveguide components at W-band. To this end, two all-pole response filters are machined by different techniques: electro-discharge and milling, and split-block: H-plane and E-plane. Some interesting results, obtained in the design, fabrication, and measure of waveguide filters at W-band, such as tolerances of the different processes and level of insertion loss, are reported.}, keywords = {antena de parche, microstrip, ranura, red de alimentaci{\'o}n}, issn = {0920-5071}, doi = {http://dx.doi.org/10.1080/09205071.2013.851011}, author = {C A Leal-Sevillano 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 {13_IETMAP_Montejo-GaraiRuiz-CruzLeal-SevillanoEtAl_ModelingofDual-PolarizationDiplexers, title = {Modeling of Dual-Polarization Diplexers Based on Enhanced Multiport Turnstile Junctions}, journal = {IET Microwaves, Antennas and Propagation}, volume = {7}, number = {7}, year = {2013}, month = {May}, pages = {485-492}, abstract = {The modelling of waveguide diplexers working simultaneously with two dual-polarisation signals is presented in this study. The proposed network is an ortho-mode junction with six physical ports based on an enhanced multiport turnstile junction. This structure is excited at the common port coming from the antenna, by two signals at different frequency bands which are required to be discriminated into dedicated ports. The added functionality of the structure presented in this work is that each frequency band can also allocate two orthogonal polarisations (dual linear or dual circular) with a very large separation between bands (fractional bandwidth larger than 55\%), using two different waveguiding concepts. The first one is based on confining the high frequencies at the centre of the axial path. The second one is just the dual, diverting the high frequencies to the outer boundaries of the axial path. The proposed structures, whose modelling and design will be addressed, are suited for low insertion loss and high-power applications, since they do not use metallic pins, irises or small waveguide sections. Moreover, as consequence of the introduced waveguiding concepts, they are very compact and short in the axial direction, which is crucial for this type of feeders in satellite applications.}, keywords = {antenna feeds, multifrequency antennas, multiplexing equipment, multiport networks, waveguide junctions}, issn = {1751-8725}, doi = {10.1049/iet-map.2012.0424}, url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=\&arnumber=6552358}, author = {Montejo-Garai, J R and J A Ruiz-Cruz and C A Leal-Sevillano and Rebollar, J M} } @article {13_IEEEMWCL_Leal-SevillanoReckJung-KubiakEtAl_SiliconMicromachinedCanonicalTHz, title = {Silicon Micromachined Canonical E-Plane and H-Plane Bandpass Filters at the Terahertz Band}, journal = {IEEE Microwave and Wireless Components Letters}, volume = {23}, number = {6}, year = {2013}, month = {June}, pages = {288-290}, abstract = {In this letter, several bandpass filters operating in the WR-1.5 band (500 to 750 GHz) are presented. The deep reactive ion etching (DRIE) silicon micromachining process is used for the fabrication of the filters. Two canonical filter topologies based on E- and H-plane are implemented. The work presented here has two specific objectives: a) to get important fabrication process parameters, such as tolerances, vertical angles, surface roughness, and repeatability and b) to validate the proper working of the waveguide filters in the terahertz band. These filters do not have any tuning element. Experimental results show better than 10 dB return loss and approximately 1 and 2.5 dB insertion loss (for 6\% fractional bandwidth) for the E- and H-plane topology, respectively. The obtained results are in agreement with fabrication tolerances of 2 micrometers and vertical angles deviations up to 3{\^A}{\textdegree}.}, keywords = {Deep reactive ion etching (DRIE), filter, micromachining, terahertz, WR-15}, issn = {1531-1309}, doi = {10.1109/LMWC.2013.2258097}, url = {http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6509458}, author = {C A Leal-Sevillano and Reck, T J and Jung-Kubiak, C and Chattopadhyay, G. and J A Ruiz-Cruz and Montejo-Garai, J R and Rebollar, J M} } @conference {12_URSIUSA_Leal-SevillanoRuiz-CruzMontejo-GaraiEtAl_DesignFiltersWband, title = {Design of waveguide filters at W-band by means of machining techniques}, booktitle = {Proc. 2012 USNC/URSI National Radio Science Meeting}, year = {2012}, month = {July}, pages = {1}, abstract = {A common part of many microwave systems is the routing of the signal between the circuit devices performing the different functions of the system (frequency discrimination, power combining, frequency conversion, signal amplifying {\^a}{\texteuro}{\textbrokenbar}). The optimum configuration of these individual devices may lead to a system layout where the interfaces of the different blocks are not aligned or even are in different planes. Thus, the routing network must have waveguide transformers, bends, and twists to be able to accommodate the signal between the different blocks. These elements have a simple function, although a careful design may be required for broadband applications. Moreover, in satellite communications, mass and volume must be kept to a minimum and compactness is highly pursued. A possible solution in these cases is to integrate some of these functions in the routing network elements or even in the input/output of the components. In this work, several waveguide devices will be shown with integrated compact elements for waveguide matching and polarization rotation. Since different functions are integrated in the same device, transitions are avoided and the total length is reduced. Very compact structures for waveguide twists have been developed in Asao et al., "A compact 90-degree twist using novel ridged waveguide for integrated waveguide subsystems," Proc. 36th EuMC, 2006 and Kirilienko et al. {\^a}{\texteuro}{\oe}Compact 90{\^A}{\textordmasculine} Twist formed by a Double-Corner-cut Square Waveguide Section{\^a}{\texteuro}, IEEE TMTT, 2008). Other structures used here will be based on Ruiz-Cruz et al., {\^a}{\texteuro}{\oe}Multi-Section Bow-Tie Steps for Full-Band Waveguide Polarization Rotation{\^a}{\texteuro}, IEEE MWCL, July 2010. The design and evaluation of the different components will be addressed in the presentation, with devices in mixed E/H plane configuration, bends and transformers. When integrating different functions in the same device, some undesired resonances may appear in the structure. Therefore, accurate CAD tools are required for simulating the response and taking into account the mode excitations inside the structure. A precise fabrication is required for having good experimental results, which will be shown in the presentation.}, author = {C A Leal-Sevillano and J A Ruiz-Cruz and Montejo-Garai, J R and Rebollar, J M} } @conference {12_URSIESP_Leal-SevillanoMontejo-GaraiMaolongEtAl_DisenoWFilterSU8, title = {Dise{\~n}o de un Filtro de Respuesta El{\'\i}ptica en Banda W Fabricado Mediante la Tecnolog{\'\i}a de Foto Resina SU-8}, booktitle = {Proc. 2012 Simposium Nacional URSI (in Spanish)}, year = {2012}, month = {Sept.}, pages = {1-4}, abstract = {Waveguide polarizers are essential devices in feeders for radio transmission systems with circular polarization. In this paper two different dual-band polarizers are designed and compared. The structure of both polarizers is based on the classical corrugated rectangular waveguide. This structure can be analyzed very efficiently like an H-plane and an E-plane problem. The Mode-Matching technique, in combination with global search algorithms, is used for the full-wave analysis and optimization of the polarizers. In the first polarizer, the height of the corrugations is designed according to a taper-type shape. For the second polarizer, no restrictions in the height of the corrugations are imposed and all the dimensions are optimized. The performance of both polarizers is compared, showing certain improvement in terms of polarization purity for the second one.}, author = {C A Leal-Sevillano and Montejo-Garai, J R and Ke Maolong and Lancaster, M. J and J A Ruiz-Cruz and Rebollar, J M} } @article {12_IEEEMWCL_Leal-SevillanoMontejo-GaraiRuiz-CruzEtAl_Low-LossEllipticalResponse, title = {Low-Loss Elliptical Response Filter at 100 GHz}, journal = {Microwave and Wireless Components Letters, IEEE}, volume = {22}, number = {9}, year = {2012}, month = {September}, pages = {459 -461}, abstract = {The design, method of fabrication and experimental validation of a pseudo-elliptical four-poles asymmetric response filter at 100 GHz with 10\% of fractional bandwidth is presented. The designed filter is part of an image radar system and must fulfill stringent specifications. The proposed topology and method of fabrication improves the out of band rejection above the pass band in comparison with other classical structures, while keeping a low insertion loss level. A two-fold geometry for implementing a transmission zero is proposed, avoiding the excitation of the first higher order mode and easing the manufacturing without any tuning element. A low-cost milling process is used for the fabrication of the device. The final design fulfills the desired specifications and presents 0.6 dB of insertion loss level at 100 GHz. The excellent agreement between simulations and measurements at this frequency band in both, return loss and insertion loss, is pointed out.}, keywords = {Asymmetric, band-pass filters, elliptic filters, extracted pole, Fabrication, fabrication method, filter, filtering theory, fractional bandwidth, frequency 100 GHz, higher order mode, image radar system, Insertion loss, loss 0.6 dB, Loss measurement, low insertion loss level, low loss, low-cost milling process, low-loss elliptical response filter, microwave filters, millimetre wave filters, Milling, out of band rejection, pseudo-elliptical four-poles asymmetric response filter, Radar, return loss, transmission zero, two-fold geometry, W-band}, issn = {1531-1309}, doi = {10.1109/LMWC.2012.2212237}, url = {http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6268297\&tag=1}, author = {C A Leal-Sevillano and Montejo-Garai, J R and J A Ruiz-Cruz and Rebollar, J M} } @conference {12_CSTUGM_Montejo-GaraiLeal-SevillanoRuiz-CruzEtAl_MultipactionBreakdownPrediction, title = {Multipaction Breakdown Prediction of Passive Microwave Devices with CST Particle-Studio}, booktitle = {2012 CST European User Group Meetings}, year = {2012}, month = {May}, keywords = {CST}, author = {Montejo-Garai, J R and C A Leal-Sevillano and J A Ruiz-Cruz and Rebollar, J M} } @article {12_IEEEMWCL_Leal-SevillanoMontejo-GaraiMaolongEtAl_Pseudo-EllipticalResponseFilterSU8, title = {A Pseudo-Elliptical Response Filter at W-Band Fabricated with Thick SU-8 Photo-Resist Technology}, journal = {IEEE Microwave and Wireless Components Letters}, volume = {22}, number = {3}, year = {2012}, month = {March}, pages = {105-107}, abstract = {The design and experimental validation of a pseudo-elliptical response filter at W-Band is presented. A micromachining technique based on the thick SU-8 photo-resist is used to construct the filter. The optimized structure is specially well-suited for the implementation of filters with transmission zeros by means of micromachining techniques, since the extracted poles are implemented by simple stubs without irises. Furthermore, a novel topology based on the use of only three SU-8 layers is presented. This new topology, which includes a novel optimized input/output routing, can be potentially used for the design of high-performance devices with a fast and low-cost production. A fourth-order filter with two transmission zeros has been fabricated (bandwidth 5\%), presenting 1.2 dB of insertion loss. This level of loss is equivalent to the actual state-of-art for micromachined filters at W-band, in spite of the reduced height and the split block in the H-plane used in the presented design.}, issn = {1531-1309}, doi = {http://dx.doi.org/10.1109/LMWC.2012.2183861}, url = {http://ieeexplore.ieee.org/xpl/articleDetails.jsp?tp=\&arnumber=6157647\&contentType=Journals+\%26+Magazines\&sortType\%3Dasc_p_Sequence\%26filter\%3DAND\%28p_IS_Number\%3A6166715\%29}, author = {C A Leal-Sevillano and Montejo-Garai, J R and Ke Maolong and Lancaster, M. J and J A Ruiz-Cruz and Rebollar, J M} } @conference {12_ESA_Montejo-GaraiRuiz-CruzRebollar_RecentResultsFiltersWBand, title = {Recent Results on Waveguide Filters at W-Band}, booktitle = {Proc. 2012 ESA Microwave Technology and Techniques Workshop}, year = {2012}, month = {Nov.}, pages = {1-6}, author = {C A Leal-Sevillano and Montejo-Garai, J R and J A Ruiz-Cruz and Rebollar, J M} } @article {12_RS_Leal-SevillanoRuiz-CruzMontejo-GaraiEtAl_RigorousanalysisofParallelPlateTEMtoPolariton, title = {Rigorous analysis of the parallel plate waveguide: From the transverse electromagnetic mode to the surface plasmon polaritons}, journal = {Radio Science}, volume = {47}, number = {RS0NO2}, year = {2012}, month = {February}, pages = {1-8}, abstract = {This paper presents an analysis of the parallel plate waveguide, based on a hybrid mode formulation. The nonideal metallic conductors of the waveguide are treated as a media characterized by an equivalent permittivity. The frequencies of interest in the presented analysis are at the terahertz band (from 300 GHz to 30 THz), and appropriate models are used for the correct characterization of metallic conductors at these frequencies. The behavior of the electromagnetic field of the fundamental mode is studied in a wide frequency range. At low frequencies (microwave regime) the fundamental mode is the well-known transverse electromagnetic (TEM) mode; as frequency increases, the electromagnetic field changes significantly and a surface wave or surface plasmon polariton (SPP) behavior is observed at the highest frequencies of the terahertz band. This paper shows a unified formulation that explains this transformation in the electromagnetic field behavior.}, issn = {0018-9480}, doi = {doi:10.1029/2011RS004838}, url = {http://onlinelibrary.wiley.com/doi/10.1029/2011RS004838/pdf}, author = {C A Leal-Sevillano and J A Ruiz-Cruz and Montejo-Garai, J R and Rebollar, J M} } @conference {12_ICEAA_Montejo-GaraiLeal-SevillanoRuiz-CruzEtAl_SymmetricalResponseFilterBartlett, title = {Symmetrical Response Filter Design Applying the Bartlett{\^a}{\texteuro}{\texttrademark}s Theorem and Using Riblet{\^a}{\texteuro}{\texttrademark}s Couplers}, booktitle = {Proc. International Conference on Electromagnetics in Advanced Applications (ICEAA)}, year = {2012}, month = {Sep.}, pages = {1-4}, keywords = {corrugated waveguide, dual-band, mode-matching, optimization, Waveguide polarizers}, author = {Montejo-Garai, J R and C A Leal-Sevillano and J A Ruiz-Cruz and Rebollar, J M} } @article {12_FED_Montejo-GaraiLeal-SevillanoRuiz-CruzEtAl_SynthesisanddesignPlasma, title = {Synthesis and design of waveguide band-stop filters without out-of-band spurious responses for plasma diagnosis}, journal = {Fusion Engineering and Design}, volume = {89}, number = {9}, year = {2012}, month = {September}, pages = {1662-1666}, issn = {0920-3796}, doi = {10.1016}, url = {http://www.sciencedirect.com/science/article/pii/S0920379612003146}, author = {Montejo-Garai, J R and C A Leal-Sevillano and J A Ruiz-Cruz and Rebollar, J M and Estrada, T} } @conference {12_IMS_Leal-SevillanoRuiz-CruzMontejo-GaraiEtAl_UpperFrequencyLimit, title = {Upper Frequency Limit of the Power Loss Method for the Estimation of Ohmic Losses in Hollow Metallic Waveguides}, booktitle = {2012 IEEE MTT-S International Microwave Symposium Digest}, year = {2012}, month = {June}, pages = {1-4}, issn = {0149-645X}, author = {C A Leal-Sevillano and J A Ruiz-Cruz and Montejo-Garai, J R and Rebollar, J M} } @conference {11_EuMC_Leal-SevillanoRuiz-CruzMontejo-GaraiEtAl_CADDual-BandPolarizersCorrugatedRectWg, title = {CAD for Dual-Band Polarizers in Corrugated Rectangular Waveguide}, booktitle = {Proc. 41st European Microwave Conference}, year = {2011}, month = {Oct.}, pages = {822-825}, abstract = {Waveguide polarizers are essential devices in feeders for radio transmission systems with circular polarization. In this paper two different dual-band polarizers are designed and compared. The structure of both polarizers is based on the classical corrugated rectangular waveguide. This structure can be analyzed very efficiently like an H-plane and an E-plane problem. The Mode-Matching technique, in combination with global search algorithms, is used for the full-wave analysis and optimization of the polarizers. In the first polarizer, the height of the corrugations is designed according to a taper-type shape. For the second polarizer, no restrictions in the height of the corrugations are imposed and all the dimensions are optimized. The performance of both polarizers is compared, showing certain improvement in terms of polarization purity for the second one.}, keywords = {corrugated waveguide, dual-band, mode-matching, optimization, Waveguide polarizers}, issn = {978-1-61284-235-6}, url = {http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=224789}, author = {C A Leal-Sevillano and J A Ruiz-Cruz and Montejo-Garai, J R and Rebollar, J M} } @conference {11_EIEC_Montejo-GaraiLeal-SevillanoRuiz-CruzEtAl_DesignofContiguous-BandOMUX, title = {Design of Contiguous-Band Elliptic-Response Manifold Output Multiplexers by Efficient Cancellation of Reactive Impedance Parts}, booktitle = {Proc. VIII Encuentro Ib{\'e}rico de Electromagnetismo Computacional (in Spanish)}, year = {2011}, month = {Nov.}, pages = {1}, abstract = {In recent years, there has been an increasing demand for satellite communication channels with a complex response, motivated by a most effective use of the radiofrequency spectrum. This means that more channels have to be combined in the output multiplexer (OMUX) after power amplification. In this paper, a synthesis technique based on the Cauer ladder development has been developed to design the singly terminated filters for manifold multiplexers. A procedure for the synthesis and design of contiguous band manifold output multiplexers based on singly terminated filters with elliptic response is considered. The zero shifting technique leads to the synthesis of a driving{\^a}{\texteuro}{\textquotedblleft}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 impedances with different frequency responses. These characteristics have been intensively analyzed to find the most suitable combination in the multiplexing process to match the channels to the manifold. Using the methodology presented in this work a four-channel multiplexer for Ku-band operation has been designed, manufactured and measured. The input{\^a}{\texteuro}{\textquotedblleft}output ports are standard WR75. The prototype has been manufactured in brass using low-cost milling technique and is formed in one block where all the cavities and irises have the same height. The unloaded Q for the brass cavities is 2500 and therefore the expected insertion losses at central frequency of the higher channel are approximately 2.5 dB. The final paper will show a comparison between the full-wave simulation using the mode-matching method (including losses) and the measurements of the input reflection coefficient and the transmission of the manufactured multiplexer.}, author = {Montejo-Garai, J R and C A Leal-Sevillano and J A Ruiz-Cruz and Rebollar, J M and Rogla, L and Sobrino, S} } @conference {11_URSIESP_Montejo-GaraiLeal-SevillanoRuiz-CruzEtAl_DisenoOMUXCancelacion, title = {Dise{\~n}o de Multiplexores Manifold de Salida y Banda Contigua con Respuesta El{\'\i}ptica Mediante la Cancelaci{\'o}n Eficiente de la Parte Reactiva de la Impedancia}, booktitle = {Proc. 2011 Simposium Nacional URSI (in Spanish)}, year = {2011}, month = {Sept.}, pages = {1-4}, abstract = {A procedure for the synthesis and design of contiguous band manifold output multiplexers based on singly terminated filters with elliptic response is presented. 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 impedances with different frequency responses. These characteristics have been intensively analyzed to find the most suitable combination in the multiplexing process to match the channels to the manifold. A Ku-band four-channel elliptic-response multiplexer has been designed in H-plane rectangular waveguide, manufactured and measured in order to show the proposed approach.}, author = {Montejo-Garai, J R and C A Leal-Sevillano and J A Ruiz-Cruz and Rebollar, J M and Rogla, L and Sobrino, S} } @conference {11_URSIESP_Leal-SevillanoRuiz-CruzMontejo-GaraiEtAl_DisenoyOptimizacionPolariz, title = {Dise{\~n}o y Optimizaci{\'o}nn de Polarizadores Doble-Banda en Gu{\'\i}a Rectangular Corrugada}, booktitle = {Proc. 2011 Simposium Nacional URSI (in Spanish)}, year = {2011}, month = {Sept.}, pages = {1-4}, abstract = {Waveguide polarizers are essential devices in feeders for radio transmission systems with circular polarization. In this paper two different dual-band polarizers are designed and compared. The structure of both polarizers is based on the classical corrugated rectangular waveguide. This structure can be analyzed very efficiently like an H-plane and an E-plane problem. The Mode-Matching technique, in combination with global search algorithms, is used for the full-wave analysis and optimization of the polarizers. In the first polarizer, the height of the corrugations is designed according to a taper-type shape. For the second polarizer, no restrictions in the height of the corrugations are imposed and all the dimensions are optimized. The performance of both polarizers is compared, showing certain improvement in terms of polarization purity for the second one.}, author = {C A Leal-Sevillano and J A Ruiz-Cruz and Montejo-Garai, J R and Rebollar, J M} } @article {11_IEEETMTT_Leal-SevillanoRuiz-CruzMontejo-GaraiEtAl_FieldCircularHollowWgNonIdealConductorsMwtoThz, title = {Field Propagation in Circular Hollow Waveguides with Non-Ideal Metallic Conductors from Microwaves to Terahertz Frequencies}, journal = {IEEE Transactions on Microwave Theory and Techniques}, volume = {59}, number = {12}, year = {2011}, month = {Dec}, pages = {3013-3022}, abstract = {A general and rigorous formulation is proposed for the analysis of hollow metallic waveguides from the gigahertz to the terahertz band. The analysis is based on a hybrid mode formulation and the Drude model for the dielectric permittivity of metallic conductors. The obtained results for the circular waveguide are compared with the classical microwave approach (surface impedance approximation or Leontovich condition). The validity range of the surface impedance approximation in both the propagation constant and the electromagnetic field pattern is studied. As a consequence, a direct relation between the error in the propagation constant and the electromagnetic field configuration is shown. Moreover, this formulation shows the evolution in the field pattern: from TE=TM modes at microwaves to the so-called Surface Plasmon Polariton at terahertz frequencies}, keywords = {Drude, hybrid mode, Leontovich, modal solution, surface impedance, Surface Plasmon Polariton (SPP), surface wave, terahertz, waveguides}, issn = {0018-9480}, url = {http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6065772\&tag=1}, author = {C A Leal-Sevillano and J A Ruiz-Cruz and Montejo-Garai, J R and Rebollar, J M} } @conference {11_MULCOPINN_Montejo-GaraiLeal-SevillanoRuiz-CruzEtAl_MultipactorpredictionBandStopFilters, title = {Multipactor prediction in waveguide band-stop filters with wideband spurious-free response}, booktitle = {Proc. International workshop on Multipactor, Corona and Passive Intermodulation (MULCOPIM)}, year = {2011}, month = {Sep.}, pages = {1-6}, keywords = {corrugated waveguide, dual-band, mode-matching, optimization, Waveguide polarizers}, url = {http://mulcopim.webs.upv.es/programme.html}, author = {Montejo-Garai, J R and C A Leal-Sevillano and J A Ruiz-Cruz and Rebollar, J M and Estrada, T} } @conference {11_URSIGAAS_Leal-SevillanoRuiz-CruzMontejo-GaraiEtAl_RigorousAnalysisofParallelPlate, title = {Rigorous Analysis of the Parallel-Plate Waveguide by the Hybrid Mode Formulation:From the TEM mode to the Surface Plasmon Polariton}, booktitle = {Proc. 2011 URSIGAAS}, year = {2011}, month = {August}, pages = {1-4}, abstract = {This paper presets an analysis of the parallel-plate waveguide, based on an hybrid mode formulation. The nonideal metallic conductors of the waveguide are treated as a media characterized by an equivalent permittivity. The frequencies of interest in the presented analysis are at the terahertz band (from 300 GHz to 30 THz) and appropriate models are used for the correct characterization of metallic conductors at these frequencies. The behavior of the electromagnetic field of the fundamental mode is studied in a wide frequency range. At low frequencies (microwave regime) the fundamental mode is the well-known TEM mode; as frequency increases, the electromagnetic field changes significantly and a surface wave or Surface Plasmon Polariton (SPP) behavior is observed at the highest frequencies of the terahertz band. This paper shows an unified formulation that explains this transformation in the electromagnetic field behavior.}, author = {C A Leal-Sevillano and J A Ruiz-Cruz and Montejo-Garai, J R and Rebollar, J M} } @article {11_MEE_OfliCrespo-ValeroRuiz-CruzEtAl_SEMCADXMicrowaveWg, title = {SEMCAD X Microwave: Enhanced Simulation of Waveguide Structures}, journal = {Microwave Engineering Europe}, volume = {September}, year = {2011}, pages = {12-15}, abstract = {A general and rigorous formulation is proposed for the analysis of hollow metallic waveguides from the gigahertz to the terahertz band. The analysis is based on a hybrid mode formulation and the Drude model for the dielectric permittivity of metallic conductors. The obtained results for the circular waveguide are compared with the classical microwave approach (surface impedance approximation or Leontovich condition). The validity range of the surface impedance approximation in both the propagation constant and the electromagnetic field pattern is studied. As a consequence, a direct relation between the error in the propagation constant and the electromagnetic field configuration is shown. Moreover, this formulation shows the evolution in the field pattern: from TE=TM modes at microwaves to the so-called Surface Plasmon Polariton at terahertz frequencies}, issn = {0332-1649}, url = {http://www.microwave-eetimes.com/en/magazine/mwee-2010.html}, author = {Ofli, E and Crespo-Valero, P and J A Ruiz-Cruz and C A Leal-Sevillano and Montejo-Garai, J R and Rebollar, J M} } @conference {11_URSIUSA_Leal-SevillanoRuiz-CruzMontejo-GaraiEtAl_WaveguideDeviceswithTwist, title = {Waveguide Devices with Integrated Polarization Twist for Broadband Applications}, booktitle = {Proc. 2011 USNC/URSI National Radio Science Meeting}, year = {2011}, month = {July}, pages = {1}, abstract = {A common part of many microwave systems is the routing of the signal between the circuit devices performing the different functions of the system (frequency discrimination, power combining, frequency conversion, signal amplifying {\^a}{\texteuro}{\textbrokenbar}). The optimum configuration of these individual devices may lead to a system layout where the interfaces of the different blocks are not aligned or even are in different planes. Thus, the routing network must have waveguide transformers, bends, and twists to be able to accommodate the signal between the different blocks. These elements have a simple function, although a careful design may be required for broadband applications. Moreover, in satellite communications, mass and volume must be kept to a minimum and compactness is highly pursued. A possible solution in these cases is to integrate some of these functions in the routing network elements or even in the input/output of the components. In this work, several waveguide devices will be shown with integrated compact elements for waveguide matching and polarization rotation. Since different functions are integrated in the same device, transitions are avoided and the total length is reduced. Very compact structures for waveguide twists have been developed in Asao et al., "A compact 90-degree twist using novel ridged waveguide for integrated waveguide subsystems," Proc. 36th EuMC, 2006 and Kirilienko et al. {\^a}{\texteuro}{\oe}Compact 90{\^A}{\textordmasculine} Twist formed by a Double-Corner-cut Square Waveguide Section{\^a}{\texteuro}, IEEE TMTT, 2008). Other structures used here will be based on Ruiz-Cruz et al., {\^a}{\texteuro}{\oe}Multi-Section Bow-Tie Steps for Full-Band Waveguide Polarization Rotation{\^a}{\texteuro}, IEEE MWCL, July 2010. The design and evaluation of the different components will be addressed in the presentation, with devices in mixed E/H plane configuration, bends and transformers. When integrating different functions in the same device, some undesired resonances may appear in the structure. Therefore, accurate CAD tools are required for simulating the response and taking into account the mode excitations inside the structure. A precise fabrication is required for having good experimental results, which will be shown in the presentation.}, author = {C A Leal-Sevillano and J A Ruiz-Cruz and Montejo-Garai, J R and Rebollar, J M} } @conference {10_EIEC_Leal-SevillanoRuiz-CruzMontejo-GaraiEtAl_NewModelSIW, title = {A New Model for the Electromagnetic Characterization of SIW}, booktitle = {Proc. VII Encuentro Ib{\'e}rico de Electromagnetismo Computacional (in Spanish)}, year = {2010}, month = {Apr.}, pages = {1-4}, author = {C A Leal-Sevillano and J A Ruiz-Cruz and Montejo-Garai, J R and Rebollar, J M} } @conference {10_URSIESP_Leal-SevillanoRuiz-CruzMontejo-GaraiEtAl_NuevoModeloparaSIW, title = {Nuevo Modelo para la Caracterizaci{\'o}n Electromagn{\'e}tica de SIW}, booktitle = {Proc. 2010 Simposium Nacional URSI (in Spanish)}, year = {2010}, month = {Sept.}, pages = {1-4}, abstract = {The Substrate Integrated Waveguide has been proposed as an alternative to planar technology in very high frequencies of the submilimeter band and in the teraherz band. For the correct analysis and design of devices like couplers, filters or antennas an accurate model for the characterization of SIW is needed. In this contribution a new model for electromagnetic characterization of SIW is proposed. The model is based on the analysis of a closed waveguide, which simulates the behavior of an open structure. For the correct simulation of the open structure a dielectric material is adjusted. Finally a pass-band filter in SIW technology is analyzed in order to verify the proposed model.}, author = {C A Leal-Sevillano and J A Ruiz-Cruz and Montejo-Garai, J R and Rebollar, J M} } @conference {10_EuCAP_Leal-SevillanoRuiz-CruzMontejo-GaraiEtAl_SimpleModelsTHz, title = {Simple Models For The Analysis Of Waveguiding Systems At The Terahertz Band Using Classical Microwave Approaches}, booktitle = {Proc. 2010 European Conference on Antennas and Propagation (EuCap)}, year = {2010}, month = {Apr.}, pages = {1-5}, abstract = {Recently the terahertz band has focused so much attention from many research groups with the aim of designing full systems. The first task before designing devices in this band is to characterize waveguide systems. In this contribution the analysis of different waveguides systems in the terahertz band is presented. The analysis is based on a hybrid mode formulation and the Drude model for the dielectric permittivity of the metallic conductor. A comparison between the exact results obtained with this last formulation and those using classical microwave approaches (surface impedance approximation or Leontovich{\^A}{\textasciiacute}s condition) is done in order to determine the validity range of the approximations in both the propagation constant and the electromagnetic field pattern.}, url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=05505379}, author = {C A Leal-Sevillano and J A Ruiz-Cruz and Montejo-Garai, J R and Rebollar, J M} }