Listar GI-GTEC - Artigos por autor "Brégains, Julio"

Mostrando ítems 21-40 de 49

    • Enhanced Time-Modulated Arrays for Harmonic Beamforming 

      Maneiro-Catoira, Roberto; Brégains, Julio; García-Naya, José A.; Castedo, Luis (Institute of Electrical and Electronics Engineers, 2017)
      [Abstract]: One of the primary features of time-modulated arrays (TMAs) is their ability to adapt their harmonic patterns to exploit the angular diversity of multipath wireless channels. In such a case, the TMA excitations ...

    • Impact of Time-Modulated Arrays on the BER of Linear Digital Modulations 

      Maneiro-Catoira, Roberto; Brégains, Julio; García-Naya, José A.; Castedo, Luis (Taylor & Francis, 2015-08-21)
      [Abstract] Time modulation provides a simple way to control the power radiation pattern of an antenna array. By appropriately selecting the parameters of a Time-Modulated Array (TMA) it is possible to obtain a reconfigurable ...

    • Matrix Pseudo-Inversion Technique for Diagnostics of Planar Arrays 

      Brégains, Julio; Ares Pena, F. J.; Moreno Piquero, E. (The Institution of Engineering and Technology, 2005-01-06)
      [Abstract] It is shown, by means of numerical simulation, that the Moore-Penrose pseudoinverse of a matrix taken from an overdetermined system can be applied to retrieve the excitation distribution of a planar array of ...

    • Measurement Effects on Ø-Symmetric Shaped Patterns Generated by Circular Continuous Apertures 

      Brégains, Julio; Ares Pena, F. J.; Moreno Piquero, E. (Institute of Electrical and Electronics Engineers, 2003-10)
      [Abstract] Sidelobe-level and ripple behaviors of Ø-symmetric shaped patterns, generated by circular, real and complex, continuous Taylor distributions, is analyzed as a function of measurement distances. This paper reveals ...

    • Multibeam Single-Sideband Time-Modulated Arrays 

      Maneiro-Catoira, Roberto; García-Naya, José A.; Brégains, Julio; Castedo, Luis (Institute of Electrical and Electronics Engineers, 2020)
      [Abstract]: The design of efficient time-modulated arrays (TMAs) for multi-beam steering purposes must be based on both a type of periodical sequences that guarantees an adequate windowing of exploited harmonics, and a ...

    • Near Field Quasi-Null Control with Far Field Sidelobe Level Maintenance in Line Source Difference Patterns 

      Brégains, Julio; Ares Pena, F. J.; Moreno Piquero, E. (Taylor & Francis, 2003)
      [Abstract] A previously developed method to place a quasi-null in a specified angular position of the near-field line source in sum patterns while, simultaneously, the far-field sidelobe level is maintained under a desired ...

    • Near-Field Quasi-Null Control with Far-Field Sidelobe Level Maintenance in Line Source Distributions 

      Brégains, Julio; Ares Pena, F. J.; Moreno Piquero, E. (The Institution of Engineering and Technology, 2002-06-06)
      [Abstract] An improving method, based on the Taylor line source, that allocates a quasi-null in a specified angular position of near-field pattern, and simultaneously controls the general topography of the far-field sidelobe ...

    • New Toroidal Beam Antennas for WLAN Communications 

      Brégains, Julio; Franceschetti, G.; Roederer, A. G.; Ares Pena, F. J. (Institute of Electrical and Electronics Engineers, 2007-02)
      [Abstract] The design of a number of new antennas that radiate linearly polarized toroidal beams is described. The developed procedures are based on the use of a method of moments commercial software tool. Several numerical ...

    • On the Feasibility of Time-Modulated Arrays for Digital Linear Modulations: a Theoretical Analysis 

      Maneiro-Catoira, Roberto; Brégains, Julio; García-Naya, José A.; Castedo, Luis (Institute of Electrical and Electronics Engineers, 2014)
      [Abstract] Wireless communications are widely based on linear digital modulation methods, which introduce the digital baseband information in the amplitude and/or in the phase of a carrier sinusoid. Time-modulated arrays, ...

    • On the Multiplicity of Solutions of Taylor Linear Sources Generating Symmetrical Power Patterns with Filled Nulls 

      Brégains, Julio; Rodríguez, J. A.; Ares Pena, F. J.; Moreno Piquero, E. (Institute of Electrical and Electronics Engineers, 2004-12)
      [Abstract] As expressed in earlier works, if filled nulls are required in a power pattern generated by a Taylor line source, their corresponding roots must be complex. This leads to a multiplicity of solutions emerged from ...

    • Optimal Synthesis Of Circular Apertures Based On Ludwig Distributions 

      Brégains, Julio; Rodríguez, J. A.; Ares Pena, F. J.; Moreno Piquero, E. (Taylor & Francis, 2003-01)
      [Abstract] Ludwig distributions are a generalization of circular Taylor distributions that generate radiation patterns with wide-angle side lobe levels decaying faster than for Taylor patterns. In this paper we show that ...

    • Optimal Synthesis of Line Source Antennas Based On Rhodes Distributions 

      Brégains, Julio; Rodríguez, J. A.; Ares Pena, F. J.; Moreno Piquero, E. (Taylor & Francis, 2002)
      [Abstract] In this paper we show that by means of an appropriate optimization technique the zeros of Rhodes radiation patterns can be perturbed so as to improve or modify pattern and/or the aperture distribution characteristics ...

    • Optimizing Uniformly Excited Linear Arrays through Time Modulation 

      Fondevila, J.; Brégains, Julio; Ares Pena, F. J.; Moreno Piquero, E. (Institute of Electrical and Electronics Engineers, 2004-12)
      [Abstract] The letter shows that, by the proper use of time modulation in equispaced linear arrays with uniform excitation distribution, it is possible to maintain the sidelobe zone of the radiated power below a certain - ...

    • Performance Analysis of Time-Modulated Arrays for the Angle Diversity Reception of Digital Linear Modulated Signals 

      Maneiro-Catoira, Roberto; Brégains, Julio; García-Naya, José A.; Castedo, Luis; Rocca, Paolo; Poli, Lorenzo (Institute of Electrical and Electronics Engineers, 2017)
      [Abstract]: Diversity occurs whenever several copies of the same transmitted signal arrive at a receiver. Such a situation allows for improving the performance of a wireless communication system transmitting over a radio ...

    • Perturbation of the Phases of Taylor Field Samples in the Synthesis of Linear and Circular Array Antennas 

      Brégains, Julio; Ares Pena, F. J.; Roederer, A. G. (Institute of Electrical and Electronics Engineers, 2004-12)
      [Abstract] Antenna design specifications do not usually restrict the phase of the radiated field. Antenna synthesis techniques generally exploit this freedom only indirectly, but direct phase perturbation can be fruitful.

    • Reply to “Comments on ‘Combining Switched TMAs and FDAs to Synthesize Dot-Shaped Beampatterns”’ 

      Maneiro-Catoira, Roberto; Brégains, Julio; García-Naya, José A.; Castedo, Luis (Institute of Electrical and Electronics Engineers, 2021)
      [Abstract]: It is noted that the main innovation contained lies in the consideration of frequency diverse arrays (FDAs) feeding networks made up of time-modulating switches (hence, the term TMA-FDA) instead of phase shifters. ...

    • Synthesis of Multi-Radial Line Antenna for HIPERLAN 

      Brégains, Julio; Ares Pena, F. J.; Franceschetti, G.; Roederer, A. G. (The Institution of Engineering and Technology, 2003-08)
      [Abstract] We present a new antenna concept - the multi-radial travelling wave line antenna - that achieves a broadband conical radiation pattern suitable for use in multiple C-band wireless computer networks.

    • Synthesis of Multiple-Pattern Planar Antenna Arrays with Single Prefixed or Jointly Optimized Amplitude Distributions 

      Brégains, Julio; Trastoy, A.; Ares Pena, F. J.; Moreno Piquero, E. (John Wiley & Sons, Inc., 2002-01-05)
      [Abstract] Previous work on the generation of multiple radiation patterns by a single linear array antenna with an unchanging excitation amplitude distribution is generalized to planar arrays. The amplitude distribution ...

    • Time Modulated Arrays: from their Origin to Their Utilization in Wireless Communication Systems 

      Maneiro-Catoira, Roberto; Brégains, Julio; García-Naya, José A.; Castedo, Luis (M D P I AG, 2017-03-14)
      [Abstract] Time-modulated arrays (TMAs) are electromagnetic systems whose radiated power pattern is controlled by the application of variable-width periodical pulses to the individual elements. The nonlinear nature of the ...

    • Time-modulated array beamforming with periodic stair-step pulses 

      Maneiro-Catoira, Roberto; Brégains, Julio; García-Naya, José A.; Castedo, Luis (Elsevier, 2020-01)
      [Abstract]: Time-modulated arrays (TMAs) are able to improve the side-lobe level of the radiation pattern at the fundamental mode but cannot steer the beam at such a mode towards a given direction. Beam-steering is possible ...