Olivier Lafond

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

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

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

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.

Scattering of Spherically and Hemispherically Stratified Lenses Fed by Any Real Source

An analytical method to compute the scattering of spherically and hemispherically stratified lens antennas is described. The expansion of any real source on spherical wave functions is detailed and validated by comparison to commercial software simulations and measurements at both 50 GHz and 77 GHz. A mode matching technique (MMT) based on spherical wave functions is first used to analyze the scattering by spherically stratified lens antennas. The far field patterns and directivity obtained are in excellent agreement with commercial software simulations and measurements for a six-shell Luneburg lens at 6 GHz. This MMT is then extended to hemispherically stratified lens antenna analysis. Its validation is also carried out by comparisons to both commercial software and measurements for a three-shell half Maxwell fish-eye lens fed by an open-ended waveguide at W-band. The expansion on spherical modes gives direct access to the field everywhere. To highlight the progressive focusing effect of inhomogeneous lens antennas, the electric field is mapped in terms of magnitude and phase in the neighborhood of the entire structure. One of the originalities of this work is the quantification of the reaction created by the scatterer on the feed. Narrowing the scatterer to a stratified lens does not affect the generality of the presented procedure. While providing controlled accuracy, the MMT tremendously reduces both computation time and memory load in comparison to commercial software.

Foam Based Luneburg Lens Antenna at 60 GHz

An innovative technological process is investigated to easily manufacture inhomogeneous Luneburg lenses. A unique foam material is drilled and pressed to achieve the difierent dielectric constant needed to follow the index law inside the lens. The performance of such 60GHz antenna is described and the antenna prototype is measured in terms of gain and radiation patterns. The results show a good e-ciency (60% with a directivity of 18{19dBi) and demonstrate the feasibility of this kind of Luneburg lens, through the use of a simple technological process. The lens with a diameter of 56mm and a thickness of 3mm operates in the 57{66GHz bandwidth. The magnitude of S11 parameter is under i10dB in the whole bandwidth and an half-power beamwidth of 5 - and 50 - in H-plane and E-plane respectively is reached.

An Active Reconfigurable Antenna at 60 GHz Based on Plate Inhomogeneous Lens and Feeders

The conception and performances of a 60 GHz active antenna, reconfigurable in terms of radiation pattern is described in this paper. This antenna is based on a plate inhomogeneous Luneburg lens fed by several ridged waveguide sources. The manufacturing technique of the plate lens is briefly described and its measured radiation patterns are given, showing the good performances of this lens. Simulated and measured radiation patterns are given for a passive lens antenna fed by several sources. The results show the beam scanning capability of this antenna. The active antenna is described and measurements of radiation patterns for several beams are given and demonstrate the beam scanning and beam shaping reconfigurability.

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

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.

Technological Process to Control the Foam Dielectric Constant Application to Microwave Components and Antennas

A technological process to control the foam dielectric constant, an important issue for the design of microwave components and antennas, is described. For that purpose, the use of different commercial foam materials has been considered. This kind of foam substrate is made of original material (Polyvinyl chloride, resin, and...) into which gas is injected. Therefore, the dielectric constant of such foam is close to one. It can be increased by expelling the gas out of the foam material. The authors are presenting the technological process used to expel the gas by pressing a foam slab at relatively low temperature (90 °C). Because of this technological process, the dielectric constant variation can be controlled by the ratio between the initial and final slab thickness. It holds a great interest for the design of microwave antennas and circuits. Indeed, the dielectric constant inside gradient index lenses (Luneburg, Maxwell fish-eye, and Fresnel lenses) must follow a particular law to obtain the desired radiation capabilities. The results of materials characterization are presented to validate the technological process. Foam-based antennas and components are also shown to illustrate the interest of the process.

Off-Axis Performances of Half Maxwell Fish-Eye Lens Antennas at 77 GHz

The off-axis performances at 77 GHz of multilayered half Maxwell fish-eye (HMFE) lenses fed by an open-ended waveguide is describes. When moving the feed with respect to (w.r.t.) the lens, it is shown that at least 40deg of scanning can be achieved. Several off-axis configurations of the lens antenna are investigated and compared using a full-wave electromagnetic software. The directivity, far field pattern and scan angle of the lens antenna are reported for a rectilinear and angular off-axis displacement of the feed and also for various distances between the feed and the lens. It is also shown that a three-shell lens is good enough to achieve a wide scan angle. Finally, off-axis measurements done with a three-shell 6.15 lambda0-diameter HMFE lens antenna are compared to computed results to validate the simulations

Wideband and high efficient aperture antenna with superstrate for 60 GHz indoor communication systems

The 60 GHz millimeter wave (MMW) radio technology is a promising candidate for fulfilling the future needs for very high bandwidth wireless connections. It enables up to gigabit-scale connection speeds to be used in indoor WLAN networks or fixed wireless connections in metropolitan areas. Generally speaking, the more speed we need the more bandwidth we need. Transmission of several hundred megabits (or even several gigabit) per second requires very large bandwidth, which is available in the millimeter wave area. Large frequency range is allocated for unlicensed wireless telecommunications around 60 GHz (typically 59 – 66 GHz) all over the world, which makes the deployment of 60 GHz systems a lot smoother operation. In Europe the frequency ranges 62 – 63 GHz and 65 −66 GHz are reserved for wideband mobile networks (MBS, Mobile Broadband System), whereas 59 – 62 GHz range is reserved for unlicensed wideband wireless local area networks (WLAN); In the United States the frequency range 57 – 64 GHz is a generally unlicensed range; In Japan 59 – 66 GHz is reserved for wireless communications [1]. These new systems will need compact and high efficiency millimeter front-ends and antennas. For antennas, printed solutions are always demanding for the researchers because of its small size, weight and ease of integration with active components [2]. Conventional antenna arrays are used for high gain applications, but in these cases, arrays of large number of elements are required which induced an increase of the size of the antenna combined with a decrease of the efficiency [3],[4]. It has been reported that for high gain, a superstrate layer can be added at a particular height of 0.5 λ0 above the ground plane [5]-[7]. This solution enables an improvement in gain of nearly 4 dB over a single parasitic patch at 12 GHz [5] and 5 dB at 10 GHz [6], but 9 dB at 60 GHz with an optimised superstrate size [7]. In this paper, the authors are proposing a wideband, high efficient and high-gain aperture antenna with superstrate for 60 GHz communication. It is known that adding a superstrate with a specific size will induce a significant effect on antenna gain and radiation patterns. The maximum measured gain of a single aperture antenna with superstrate is 13.1 dBi, which is higher than that of a classical 2 × 2 array. The measured gain of a single antenna with superstrate compared to the basic aperture antenna shows an increase of 8 dB at 60 GHz. This superstrate antenna gives an estimated efficiency of 79%. The measured 2:1 VSWR bandwidth is 15%, that covers the 60 GHz application band, which is one advantage of this antenna configuration compared to reference [7]. The radiation patterns are found to be broadside all over the frequency band with very low back radiation. Hence aperture antenna with superstrate is a good candidate for wideband, high efficient high gain application at 60 GHz.