@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 {08_IJRFMiCAE_FahmiRuiz-CruzZaki_EandH-plane, title = {E and H-plane wide-band ridge waveguide couplers}, journal = {International Journal of RF and Microwave Computer-Aided Engineering}, volume = {18}, number = {4}, year = {2008}, month = {July}, pages = {348-358}, abstract = {A systematic synthesis procedure for ridge waveguide branch line couplers in both E-plane and H-plane configurations is presented. Ridge waveguides are chosen to benefit from their wide mono-mode band and compact size compared to rectangular waveguides. Equivalent circuit parameters are used to synthesize the coupler sections. Rigorous mode matching method is used for full-wave analysis and optimization of the couplers. Ridge couplers both in empty waveguide and Low Temperature Co-fired Ceramic "LTCC" technology are designed using the proposed method and the design is verified with another numerical method. A prototype is built and its response is measured to verify the approach}, keywords = {full-wave, LTCC, mode matching, optimization, ridge waveguide}, issn = {1096-4290}, doi = {10.1002/mmce.20293}, url = {http://www3.interscience.wiley.com/cgi-bin/fulltext/119140987/PDFSTART}, author = {Fahmi, M M and J A Ruiz-Cruz and Zaki, K A} } @conference {07_IMS_Ruiz-CruzZhangRebollarEtAl_TEMMode-MatchingAnalysis, title = {TEM Mode-Matching Analysis of Multi-coupled Strip-line Filters}, booktitle = {2007 IEEE MTT-S International Microwave Symposium Digest}, year = {2007}, month = {June}, pages = {541-544}, abstract = {The analysis of multi-coupled strip-line filters by the mode-matching method is studied for different input/output excitations. The aim is to compare the computational effort of two different options and to propose the most suitable formulation for the design of some strip-line filters. It is shown that a suitable segmentation of the structure is essential for obtaining good numerical results. In fact, if the optimum segmentation is selected, a mode-matching analysis using only TEM modes can resemble the full-wave response, with shorter computation time. Hence, this approach can be very useful in design and different examples are shown to validate it, using other numerical methods and measurements of a ten order filter.}, keywords = {microwave filters, mode matching, multicoupled strip-line filter design, optimum structure segmentation, strip line filtersTEM mode-matching analysis}, issn = {0149-645X}, doi = {10.1109/MWSYM.2007.380546}, url = {http://ieeexplore.ieee.org/iel5/4263706/4263707/04263871.pdf?tp=\&isnumber=\&arnumber=4263871}, author = {J A Ruiz-Cruz and Zhang, Y and Rebollar, J M and Zaki, K A and Montejo-Garai, J R and Piloto, A J} } @conference {06_IMS_Ruiz-CruzMontejo-GaraiRebollarEtAl_ComputerAidedDesign, title = {Computer Aided Design of Wideband Orthomode Transducers based on the Boifot Junction}, booktitle = {2006 IEEE MTT-S International Microwave Symposium Digest}, year = {2006}, month = {June}, pages = {1173-1176}, abstract = {A CAD tool based on the Boslashifot junction is proposed for the design of wideband orthomode transducers (OMTs). It has two interesting features. First, the OMT routing branches use well-known waveguide elements, such as truncated E-plane bends, which can be efficiently analyzed by mode-matching (MM) methods and can achieve wideband performance. Second, a MM technique is presented for the four-port Boslashifot junction, which provides its generalized multimode characterization. As a result, the whole OMT is segmented into different regions, yielding an efficient CAD tool for its optimum design. The analysis method and the designed OMT have been validated with other numerical methods and experimental results}, keywords = {CAD, computer aided design, four-port junction, mode matching, mode-matching methods, OMT routing branches, transducers, waveguide componentsCAD tool, waveguide elements, wideband orthomode transducers}, issn = {0149-645X}, doi = {10.1109/MWSYM.2006.249400}, url = {http://ieeexplore.ieee.org/iel5/4014788/4014789/04015130.pdf?tp=\&isnumber=\&arnumber=4015130}, author = {J A Ruiz-Cruz and Montejo-Garai, J R and Rebollar, J M and Montesano, C E and Mart{\i}n, M J and Naranjo-Masi, M} } @conference {06_EuMC_Montejo-GaraiRuiz-CruzRebollarEtAl_DesignofSelf-Equalised, title = {Design of Self-Equalised Elliptic Filter Channels in Ka-Band Implemented in Rectangular H-Plane Waveguide}, booktitle = {Proc. 36th European Microwave Conference}, year = {2006}, month = {Sept.}, pages = {1087-1090}, abstract = {In this article, a systematic design procedure for the design of self-equalised elliptic filters in H-plane configuration is presented. Such a configuration in tends to be an alternative to the classical dual-mode circular waveguide configuration in Ka band, with the aim in mind of reducing cost and computation time. In order to decrease the insertion loss the TE105 will be used. A sixth order filter with two transmission zeros at finite real frequencies and two zeros for equalisation has been designed, manufactured and measured. The results make clear the validity of the proposed configuration}, keywords = {dual mode circular waveguide, elliptic filter channels, elliptic filters, Ka-band, microwave filters, Milling, mode matching, poles and zeros, rectangular waveguide, rectangular waveguides, self-equalised filter, systematic design procedure, waveguide filtersH-plane configuration}, issn = {2-9600551-6-0}, doi = {10.1109/EUMC.2006.281123}, url = {http://ieeexplore.ieee.org/iel5/4057701/4057702/04058013.pdf?tp=\&isnumber=\&arnumber=4058013}, author = {Montejo-Garai, J R and J A Ruiz-Cruz and Rebollar, J M and Onoro-Navarro, A. and Hidalgo-Carpintero, I and Padilla-Cruz, M J} } @conference {06_IMS_ZhangRuiz-CruzZaki_RidgeWaveguideDivider, title = {Ridge Waveguide Divider Junctions for Wide-Band Multiplexer Applications}, booktitle = {2006 IEEE MTT-S International Microwave Symposium Digest}, year = {2006}, month = {June}, pages = {1225-1228}, abstract = {Ridge waveguide divider junctions are introduced and applied to wide-band multiplexer applications. A rigorous analysis and optimization process by mode matching method (MMM) is employed to design the junctions that yield low reflection coefficient in common port and almost equal transmission coefficients in the other two ports over a wide frequency band. Two design examples of wide-band diplexer and triplexer using such junctions are presented. All the components involved in the diplexer/triplexer designs are rigorously modeled and cascaded by MMM. Optimization procedures by MMM are also applied in these two designs to improve the performance. Multiplexers using such junctions can be built in either metallic form or low-temperature co-fired ceramic (LTCC) technology}, keywords = {low-temperature co-fired ceramics, mode matching, mode matching method, multiplexing equipment, ridge waveguide divider junctions, ridge waveguides, waveguide junctionsLTCC technology, wide-band diplexer, wide-band multiplexer applications, wide-band triplexer}, issn = {0149-645X}, doi = {10.1109/MWSYM.2006.249431}, url = {http://ieeexplore.ieee.org/iel5/4014788/4014789/04015143.pdf?tp=\&isnumber=\&arnumber=4015143}, author = {Zhang, Y and J A Ruiz-Cruz and Zaki, K A} } @conference {06_EuMC_Ruiz-CruzZhangFahmiEtAl_RidgeWaveguideElliptic, title = {Ridge Waveguide Elliptic Filters in Narrow-Wall Canonical Configuration}, booktitle = {Proc. 36th European Microwave Conference}, year = {2006}, month = {Sept.}, pages = {1080-1082}, abstract = {A new canonical ridge waveguide structure is proposed to design elliptic filter responses. The non-adjacent cavities are coupled by windows situated at the common narrow-wall of the ridge waveguide enclosures. This new configuration provides positive and negative cross couplings using evanescent rectangular waveguides and metallic strips, respectively. The full-wave analysis of the structure is carried out by a rigorous mode matching method. The design is based on circuit synthesis and full-wave optimization. Finally, the proposed structure is elucidated with the design of a four-pole filter and it is validated with the commercial HFSS software}, keywords = {circuit synthesis, elliptic filters, four-pole filter, full-wave optimization, metallic strips, mode matching, mode matching method, narrow-wall canonical configuration, negative cross couplings, network synthesis, nonadjacent cavities, positive cross couplings, rectangular waveguides, ridge waveguide elliptic filters, ridge waveguides, waveguide filtersHFSS software}, issn = {2-9600551-6-0}, doi = {10.1109/EUMC.2006.281121}, url = {http://ieeexplore.ieee.org/iel5/4057701/4057702/04058011.pdf?tp=\&isnumber=\&arnumber=4058011}, author = {J A Ruiz-Cruz and Zhang, Y and Fahmi, M M and Zaki, K A} } @article {05_IEEETMTT_Ruiz-CruzSabbaghZakiEtAl_Canonicalridgewaveguide, title = {Canonical ridge waveguide filters in LTCC or metallic resonators}, journal = {IEEE Transactions on Microwave Theory and Techniques}, volume = {53}, number = {1}, year = {2005}, month = {Jan.}, pages = {174-182}, abstract = {A new physical realization of an elliptic function filter response is proposed for achieving compact size, wide bandwidth, wide spurious free stopband and high-selectivity performance. The filter configuration can be implemented in conventional waveguide technology or embedded in a multilayer low-temperature co-fired ceramic structure for integration with other circuitry in a chip module. The filter is analyzed using rigorous mode matching. To validate the concept, prototypes of four- and six-cavity elliptic filters are designed following a systematic procedure. Approximate synthesis is used to obtain initial dimensions of the filter and the desired optimum response is obtained by means of a final full-wave optimization. The results are verified with other numerical methods and with the measurements of a fourth-order waveguide filter.}, keywords = {band-pass filters, canonical ridge waveguide filters, cavity resonator filters, ceramics, chip module, circuit optimisation, elliptic filters, elliptic function filter response, four cavity elliptic filters design, fourth order waveguide filter, full-wave optimization, metallic resonators, microwave filters, mode matching, multilayer low temperature cofired ceramic structure, multilayers, numerical methods, prototypes, resonators, ridge waveguides, six cavity elliptic filters design, spurious free stopband filter, waveguide filters band pass filters, waveguide technology}, issn = {0018-9480}, doi = {10.1109/TMTT.2004.839324}, url = {http://ieeexplore.ieee.org/iel5/22/30125/01381687.pdf?tp=\&arnumber=1381687\&isnumber=30125}, author = {J A Ruiz-Cruz and El Sabbagh, M A and Zaki, K A and Rebollar, J M and Zhang, Y} } @article {05_IEEETMTT_Montejo-GaraiRuiz-CruzRebollar_Full-WaveDesignof, title = {Full-Wave Design of H-Plane Contiguous Manifold Output Multiplexers Using the Fictitious Reactive Load Concept}, journal = {IEEE Transactions on Microwave Theory and Techniques}, volume = {53}, number = {8}, year = {2005}, month = {Aug.}, pages = {2628-2632}, abstract = {In this paper, a new procedure for the design of contiguous band manifold output multiplexers in$H$-plane configuration is presented. Such a configuration eliminates the slots between the T-junctions and the filters allowing high power handling, as well as dramatically reducing the risk of multipactor. This paper pursues the division of the design into tasks with low computational effort. The approach comprises: 1) the singly terminated synthesis of the channel filters and their corresponding full-wave responses; 2) the manifold design using fictitious reactive loads simulating the phase response of every channel out of its corresponding band; and 3) the final full-wave optimization of the whole structure using the simulated-annealing method. In order to validate the above procedure, a five-channel$Ku$-band multiplexer has been designed, manufactured, and measured.}, keywords = {mode matching, multiplexer, simulated annealing, singly terminated filter}, issn = {0018-9480}, doi = {10.1109/TMTT.2005.852749}, url = {http://ieeexplore.ieee.org/iel5/22/32085/01492665.pdf?tp=\&isnumber=\&arnumber=1492665}, author = {Montejo-Garai, J R and J A Ruiz-Cruz and Rebollar, J M} } @conference {05_IMS_FahmiRuiz-CruzZakiEtAl_LTCCwide-bandcanonical, title = {LTCC wide-band canonical ridge waveguide filters}, booktitle = {2005 IEEE MTT-S International Microwave Symposium Digest}, year = {2005}, month = {June}, pages = {249-252}, abstract = {A canonical LTCC ridge waveguide filter for wide-band application is proposed. A new coupling scheme is employed to achieve the values of the cross couplings needed to increase the bandwidth. The change of the realization of the coupling sections from rectangular to narrow ridge waveguide is shown to eliminate detrimental undesired cross coupling. To validate the concept, rigorous mode matching method is used for full-wave analysis and optimization of a six pole filter. The response is verified with another numerical method, and a prototype is constructed for testing.}, keywords = {canonical ridge waveguide filters, ceramic packaging, coupling scheme, coupling sections, full-wave analysis, mode matching, mode matching method, narrow ridge waveguide, optimisation, ridge waveguides, six pole filter, waveguide filters LTCC, wide-band filters}, issn = {01490-645X}, doi = {10.1109/MWSYM.2005.1516572}, url = {http://ieeexplore.ieee.org/iel5/10171/32491/01516572.pdf?tp=\&isnumber=\&arnumber=1516572}, author = {Fahmi, M M and J A Ruiz-Cruz and Zaki, K A and Piloto, A J} } @conference {05_IMS_Ruiz-CruzZakiMontejo-GaraiEtAl_Rectangularwaveguideelliptic, title = {Rectangular waveguide elliptic filters with capacitive and inductive irises and integrated coaxial excitation}, booktitle = {2005 IEEE MTT-S International Microwave Symposium Digest}, year = {2005}, month = {June}, pages = {269-272}, abstract = {CAD of rectangular waveguide filters with elliptic responses is described. The configuration uses capacitive and inductive irises in order to achieve the different coupling signs required to synthesize finite transmission zeros in the rejection bands. The input and output ports are realized by a coaxial probe that directly excites the input/output cavities. The analysis is done by the efficient mode-matching method, in order to allow a final full-wave optimization taking into account all the higher order mode interactions. The CAD results are verified with the HFSS and a filter was manufactured for testing.}, keywords = {band-stop filters, capacitive iris, circuit CAD, coaxial probe, coaxial waveguides, elliptic filters, finite transmission zeros, full-wave optimization, higher order mode interactions, inductive iris, input ports, integrated coaxial excitation, mode matching, mode-matching method, optimisation, output ports, rectangular waveguide filter, rectangular waveguides, rejection bands, waveguide filters CAD}, issn = {01490-645X}, doi = {10.1109/MWSYM.2005.1516577}, url = {http://ieeexplore.ieee.org/iel5/10171/32491/01516577.pdf?tp=\&isnumber=\&arnumber=1516577}, author = {J A Ruiz-Cruz and Zaki, K A and Montejo-Garai, J R and Rebollar, J M} } @conference {05_IMS_Ruiz-CruzZhangZakiEtAl_Ridgewaveguidebranch-line, title = {Ridge waveguide branch-line directional couplers for wideband applications and LTCC technology}, booktitle = {2005 IEEE MTT-S International Microwave Symposium Digest}, year = {2005}, month = {June}, pages = {1219-1222}, abstract = {A new branch-line directional coupler is proposed for achieving wide bandwidth. The device is implemented in ridge waveguide to exploit its wide monomode band. It can be physically realized either in empty ridge waveguide or in LTCC for integration in a chip module. Two prototypes of two and five branches are designed following a systematic procedure. An appropriate equivalent circuit provides initial dimensions and the desired optimum response is obtained by means of a final full-wave optimization based on the rigorous and efficient mode-matching method. The results are verified with the finite element method of the HFSS software and a prototype will be manufactured for testing}, keywords = {branch-line directional couplers, chip module integration, directional couplers, equivalent circuits, finite element analysis, finite element method, full-wave optimization, mode matching, mode-matching method, optimisation, ridge waveguides, ridge waveguidesLTCC technology, wide monomode band}, issn = {01490-645X}, doi = {10.1109/MWSYM.2005.1516896}, url = {http://ieeexplore.ieee.org/iel5/10171/32491/01516896.pdf?tp=\&isnumber=\&arnumber=1516896}, author = {J A Ruiz-Cruz and Zhang, Y and Zaki, K A and Piloto, A J and Rebollar, J M} } @conference {04_IMS_LiuRuiz-CruzWangEtAl_extremelywidebandridge, title = {An extremely wideband ridge waveguide filter}, booktitle = {2004 IEEE MTT-S International Microwave Symposium Digest}, volume = {2}, year = {2004}, month = {June}, pages = {615-618}, abstract = {An extremely wideband ridge waveguide filter is presented. The fractional bandwidth of the filter can be greater than 115\%. An input and output transition from ridge waveguide to stripline and then to coax is also designed. The analysis is done with mode matching method and verified with Ansoft HFSS. For validation purpose, a test filter with pass band from 3 GHz to 9 GHz has been designed. The results by both mode matching method and Ansoft HFSS are presented. Excellent agreement is obtained. The test filter is designed using air filled ridge waveguide; however the same design procedure can be equally applied to other manufacturing techniques such as LTCC.}, keywords = {air filled ridge waveguide, fractional bandwidth, mode matching, mode matching method, ridge waveguides, strip lines, stripline, waveguide filters 3 to 9 GHz, wideband ridge waveguide filter}, issn = {0149-645X}, doi = {10.1109/MWSYM.2004.1336059}, url = {http://ieeexplore.ieee.org/iel5/9277/29472/01336059.pdf?tp=\&isnumber=\&arnumber=1336059}, author = {Liu, Z M and J A Ruiz-Cruz and Wang,C and Zaki, K A} } @conference {04_IMS_Ruiz-CruzElZakiEtAl_Full-wavedesignof, title = {Full-wave design of canonical ridge waveguide filters}, booktitle = {2004 IEEE MTT-S International Microwave Symposium Digest}, volume = {2}, year = {2004}, month = {June}, pages = {603-606}, abstract = {A new physical realization of an elliptic function filter response is proposed for achieving compact size, wide bandwidth, wide spurious free stop band and high selectivity performance. The canonical ridge waveguide filter configuration is analyzed using rigorous mode-matching. To validate the concept, a prototype that realizes the coupling matrix of a canonical four cavity elliptic filter is designed following a systematic procedure. Approximate synthesis is used to obtain initial dimensions of the filter and the desired optimum response is obtained by means of a final full-wave optimization. The results are verified with other numerical method and a prototype will be built for testing.}, keywords = {band-pass filters, coupling matrix, elliptic filters, elliptic function filter, filtering theory, full-wave design, full-wave optimization, mode matching, mode-matching, waveguide filters canonical ridge waveguide filters, wide bandwidth, wide spurious free stop band}, issn = {0149-645X}, doi = {10.1109/MWSYM.2004.1336056}, url = {http://ieeexplore.ieee.org/iel5/9277/29472/01336056.pdf?tp=\&isnumber=\&arnumber=1336056}, author = {J A Ruiz-Cruz and El Sabbagh, M A and Zaki, K A and Rebollar, J M} } @conference {04_APS_Ruiz-CruzZakiRebollar_Mode-matchinganalysisof, title = {Mode-matching analysis of a coaxial-to-stripline discontinuity applied to the modeling of a coaxial probe}, booktitle = {Proc. 2004 IEEE Antennas and Propagation Society International Symposium}, volume = {2}, year = {2004}, month = {June}, pages = {2139-2142}, abstract = {The paper presents the analysis of the discontinuity between a coaxial and a generalized stripline waveguide and its application to the characterization of a probe inside a rectangular waveguide. The probe is modeled by a stripline whose inner conductor is stepped. For thin probes, just a reduced number of sections is needed and its characterization can be obtained very efficiently. The mode-matching technique is employed for analyzing the basic discontinuity, and the inner cross products between the modes are computed by means of the Bessel-Fourier series, reducing the computation time with respect to a pure numerical integration. The simulation results are compared with those obtained by other numerical techniques.}, keywords = {coaxial probe modeling, coaxial waveguide, coaxial waveguides, coaxial-to-stripline discontinuity, computation time, Fourier series, mode matching, mode-matching analysis, numerical integration, rectangular waveguide, strip line discontinuities Bessel-Fourier series, stripline waveguide}, issn = {0-7803-8302-8}, doi = {10.1109/APS.2004.1330633}, url = {http://ieeexplore.ieee.org/iel5/9253/29356/01330633.pdf?tp=\&isnumber=\&arnumber=1330633}, author = {J A Ruiz-Cruz and Zaki, K A and Rebollar, J M} } @conference {03_APS_Ruiz-CruzRebollar_BCMManalysisof, title = {BCMM analysis of short-slot waveguide couplers with an FFT algorithm}, booktitle = {Proc. 2003 IEEE Antennas and Propagation Society International Symposium}, volume = {2}, year = {2003}, month = {June}, pages = {1193-1196}, abstract = {In this contribution, the analysis of the short-slot directional waveguide couplers by means of a boundary contour mode-matching method (BCMM method) is presented. A new formulation is proposed that uses the FFT to improve the efficiency of the technique. The advantages and difficulties of the application of the BCMM for solving this kind of structure are also discussed. Simulated results are compared with those obtained by other numerical techniques. Experimental measurements are shown.}, keywords = {BCMM method, boundary contour mode-matching method, boundary-value problems, fast Fourier transforms, FFT algorithm, measurements, mode matching, numerical techniques, short-slot directional waveguide couplers, short-slot waveguide couplers, slot lines, waveguide couplers BCMM analysis}, issn = {0-7803-7846-6}, doi = {10.1109/APS.2003.1219449}, url = {http://ieeexplore.ieee.org/iel5/8636/27400/01219449.pdf?tp=\&isnumber=\&arnumber=1219449}, author = {J A Ruiz-Cruz and Rebollar, J M} } @article {03_IEEPMAP_Ruiz-CruzEstebanRebollar_Efficientboundarycontour, title = {Efficient boundary contour mode-matching method of H- and E-plane junctions by fast Fourier transform algorithm}, journal = {IEE Proceedings Microwaves, Antennas and Propagation}, volume = {150}, number = {5}, year = {2003}, month = {Oct.}, pages = {332-338}, abstract = {An efficient boundary contour mode-matching method (BCMM) is applied to the analysis of H- and E-plane junctions with planar and circular boundaries. The proposed approach is based on the use of the fast Fourier transform (FFT) to improve an analytical BCMM method. The electromagnetic field inside the structure is expressed in terms of circular waves, whereas in the rectangular ports a modal expansion is used. Depending on the shape of the contour, the original field expansion is rewritten in plane waves or in other sets of circular waves, replacing the conventional numerical integrations by a new, more suitable procedure. Finally, the transformation between the different expansions is carried out by means of the FFT, increasing notably the efficiency of the method. The presented formulation is verified by comparing simulated results with those obtained by other numerical techniques}, keywords = {boundary contour mode-matching method, circular boundary, circular waves, coupling integrals, efficient method, electromagnetic field, electromagnetic fields, fast Fourier transform algorithm, fast Fourier transforms, FFT algorithm, field expansion, fullwave analysis, H-plane junctions, junction matrix, mode matching, planar boundary, plane waves, simulated results, waveguide junctions E-plane junctions}, issn = {1350-2417}, doi = {10.1049/ip-map:20030775}, url = {http://ieeexplore.ieee.org/iel5/2196/28221/01262347.pdf?tp=\&isnumber=\&arnumber=1262347}, author = {J A Ruiz-Cruz and Esteban,J and Rebollar, J M} }