Olivier Lafond

Bio: Olivier Lafond is an academic researcher from University of Rennes. The author has contributed to research in topics: Antenna (radio) & Antenna measurement. The author has an hindex of 15, co-authored 103 publications receiving 1050 citations. Previous affiliations of Olivier Lafond include École Normale Supérieure & Canon Inc..

High-Efficient and High-Gain Superstrate Antenna for 60-GHz Indoor Communication

Abstract: A high-efficient and high-gain aperture coupled patch antenna with superstrate at 60 GHz is studied and presented. It is noted that adding superstrate will result in a significant effect on the antenna performances, and the size of the superstrate is critical for the optimum performance. The maximum measured gain of a single antenna with superstrate is 14.6 dBi, which is higher than that of a classical 2 x 2 array. It is found that the gain measured of a single antenna with superstrate increases nearly 9 dB at 60 GHz over its basic patch antenna. This superstrate antenna gives a very high estimated efficiency of 76%. The 2:1 measured VSWR bandwidth with superstrate is 6.8%. The radiation patterns are found to be broadside all over the frequency band. Also, this letter explains a comparison to another source of parasitic patch superstrate antenna with normal microstrip coupling. It is found that aperture coupling is better for high-gain antenna applications.

Design Optimization of Multishell Luneburg Lenses

Abstract: Guidelines are provided for designing multishell Luneburg lenses (LL) whatever the primary source is. Three different optimization problems that minimize three different norms of the discrepancy between the ideal relative permittivity and the reconstructed one with respect to the thickness and permittivity of each shell are detailed. The performances of the three so-optimized LL are compared by simulations with those of previously proposed approaches. The highest directivity is obtained for the minmax norm. An investigation of the influence of the number of shells on the lens antenna performances, directivity, sidelobe levels and aperture efficiencies for various lens diameters, is also proposed in order to better know how to choose these parameters. Finally, measurements done with a multishell Luneburg lens fed by a waveguide are compared with simulations to show, through excellent agreements between theory and measurements, the validity of this study

Design and characterization of half Maxwell fish-eye lens antennas in millimeter waves

Abstract: This paper presents the performance of multilayered half Maxwell fish-eye (HMFE) lenses fed by aperture-coupled microstrip patch antennas. Manufacturing techniques are reviewed and the shell technique is retained. Many lens configurations are investigated and compared using a full-wave electromagnetic software at 50 GHz. We report the effects of the number of shells, diameter of the lens, and distance between the primary source and the lens on the input impedance, broadside directivity, and aperture efficiency. Thus, we show that aperture efficiencies up to 95% can be obtained for a one-wavelength-diameter lens with only three shells, justifying the interest in such lenses. An analytical optimization method is also proposed and detailed to choose the thickness and permittivity of a three-shell HMFE lens to approach the radial permittivity law as well as possible. Simulations of lens antennas whose shell characteristics are determined by various ways show that the optimized lens is the one that provides the highest broadside directivities. Finally, measurements done with a three-shell four-wavelength diameter lens fed by a 2 times 2 patch antenna array show the validity of these simulations. To our knowledge, this represents the first layered HMFE lens carried out in the millimeter-wave frequency range

Ka-Band Phased Array Antenna for High-Data-Rate SATCOM

Abstract: The general issue of this letter deals with the design of a phased array antenna for high-data-rate SATCOM. A final demonstrator antenna could be installed on an unmanned aerial vehicle (UAV) to communicate with a satellite in Ka-band. First, a compact reflection-type phase shifter is designed and realized. Second, the conception of a phased array antenna prototype is detailed. Third, a new calibration method is involved that can provide the bias voltage to be applied to each phase shifter in order to scan the beam in the desired direction.

Performance and Radiation Patterns of a Reconfigurable Plasma Corner-Reflector Antenna

Abstract: A novel reconfigurable plasma corner reflector antenna is proposed to better collimate the energy in forward direction operating at 2.4 GHz. Implementation of a low-cost plasma element permits beam shape to be changed electrically. The maximum measured gains are 5.7, 10.8, and 10.5 dBi for the omnidirectional, single-, and double-beam shapes, respectively.

Approximation theory and methods, by M. J. D. Powell. Pp 339. £25 (hardcover), £8·50 (paperback). 1981. ISBN 0-521-22472-1/29514-9 (Cambridge University Press)

Abstract: Preface 1. The approximation problem and existence of best approximations 2. The uniqueness of best approximations 3. Approximation operators and some approximating functions 4. Polynomial interpolation 5. Divided differences 6. The uniform convergence of polynomial approximations 7. The theory of minimax approximation 8. The exchange algorithm 9. The convergence of the exchange algorithm 10. Rational approximation by the exchange algorithm 11. Least squares approximation 12. Properties of orthogonal polynomials 13. Approximation of periodic functions 14. The theory of best L1 approximation 15. An example of L1 approximation and the discrete case 16. The order of convergence of polynomial approximations 17. The uniform boundedness theorem 18. Interpolation by piecewise polynomials 19. B-splines 20. Convergence properties of spline approximations 21. Knot positions and the calculation of spline approximations 22. The Peano kernel theorem 23. Natural and perfect splines 24. Optimal interpolation Appendices Index.

Multibeam Antenna Technologies for 5G Wireless Communications

Abstract: With the demanding system requirements for the fifth-generation (5G) wireless communications and the severe spectrum shortage at conventional cellular frequencies, multibeam antenna systems operating in the millimeter-wave frequency bands have attracted a lot of research interest and have been actively investigated. They represent the key antenna technology for supporting a high data transmission rate, an improved signal-to-interference-plus-noise ratio, an increased spectral and energy efficiency, and versatile beam shaping, thereby holding a great promise in serving as the critical infrastructure for enabling beamforming and massive multiple-input multiple-output (MIMO) that boost the 5G. This paper provides an overview of the existing multibeam antenna technologies which include the passive multibeam antennas (MBAs) based on quasi-optical components and beamforming circuits, multibeam phased-array antennas enabled by various phase-shifting methods, and digital MBAs with different system architectures. Specifically, their principles of operation, design, and implementation, as well as a number of illustrative application examples are reviewed. Finally, the suitability of these MBAs for the future 5G massive MIMO wireless systems as well as the associated challenges is discussed.

Statistical Characterization of 60-GHz Indoor Radio Channels

Abstract: An extensive review of the statistical characterization of 60-GHz indoor radio channels is provided from a large number of published measurement and modeling results. First, the most prominent driver applications for 60 GHz are considered in order to identify those environment types that need to be characterized most urgently. Large-scale fading is addressed yielding path-loss parameter values for a generic 60-GHz indoor channel model as well as for the office environment in particular. In addition, the small-scale channel behavior is reviewed including the modeling of time-of-arrival and angle-of-arrival details and statistical parameters related to delay spread, angular spread and Doppler spread. Finally, some research directions for future channel characterization are given.

A 3-D Luneburg Lens Antenna Fabricated by Polymer Jetting Rapid Prototyping

Abstract: In this work, we designed, built, and tested a low-gain 20 dBi Luneburg Lens antenna using a rapid prototyping machine as a proof of concept demonstrator. The required continuously varying relative permittivity profile was implemented by changing the size of plastic blocks centered on the junctions of a plastic rod space frame. A 12-cm ( 4λ0 at 10 GHz) diameter lens is designed to work at X-band. The effective permittivity of the unit cell is calculated by effective medium theory and simulated by full-wave finite-element simulations. The fabrication is implemented by a polymer jetting rapid prototyping method. In the measurement, the lens antenna is fed by an X-band waveguide. The measured gain of the antenna at X-band is from 17.3 to 20.3 dB. The measured half-power beam width is from 19° to 12.7° while the side lobes are about 25 dB below the main peak. Good agreement between simulation and experimental results is obtained.