An electronically reconfigurable transmitarray device at 12 GHz is presented in this work. This paper highlights the functioning of this kind of device and thoroughly examines the proposed reconfigurable transmitarray. The architecture is discussed along with the design and selection of all the constituting elements and the prototypes for all of them. In order to add reconfigurability to the transmitarray structure, 360° reflective phase shifters were designed, prototyped and validated for direct application. Eventually, a demonstrative prototype for an active transmitarray with phase shifters was assembled, and radiation pattern measurements were taken in an anechoic chamber to demonstrate the capabilities of this structure.

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Electronically Reconfigurable Transmitarray at Ku Band for Microwave Applications

An electronically reconfigurable unit cell with 1-bit phase quantization (0°/180°) is proposed for X-band linear polarization transmit arrays. It consists of two rectangular patch antennas loaded by U- and O-slots and connected by a metallized via-hole. The transmission phase is controlled using two p-i-n diode switches integrated in the O-slot. An equivalent lumped-element circuit model is implemented and compared successfully to full-wave simulations. The numerical results are validated experimentally using an ad-hoc waveguide simulator. The prototype exhibits low insertion loss (1.8 dB) with the same level for both phase states, a broad 3-dB transmission bandwidth (14.7%), a 1-dB compression point of 13-15 dBm, and a gain of 5 dBi at 9.75 GHz. The performance and simplicity of the proposed unit cell make it attractive to build electronically steerable transmit arrays in X-band.

1-Bit Reconfigurable Unit Cell Based on PIN Diodes for Transmit-Array Applications in $X$ -Band

A simple mechanical beam steering antenna concept is proposed for ground mobile terminals of Ka-band satellite and high altitude platform (HAP) providing broadband access services. The wide-angle elevation beam steering is achieved by in-plane translation of a thin offset flat lens in front of a stationary primary feed while full azimuth coverage is obtained by simple 360° rotation of the lens. A new strategy is also proposed to reduce the effective F/D of the focusing system and consequently the total antenna height without increasing beam distortion: a second small flat lens is added on top of the primary feed to create a virtual focus located well below the feed phase center. The challenge is to conciliate high gain both with wide beam scanning and reduced antenna height. Design rules are presented for this antenna concept along with a 27.3-dBi gain fabricated example for the up-link Ka-band (29.5–30 GHz), with circular polarization, 0° to 50° elevation scan, better than 2.8-dB scan loss and an effective F/D of only 0.55. Both lenses are 3.35-mm thick, formed by a suitable assembly of phase shifting unit cells with less than 0.4 dB of transmission loss in simulation. The main lens dimensions are $195\;\text{mm} \times 145\;\text{mm}$ and its weight is 215 g. Total antenna height, including the feed is 84 mm.

Circular Polarization Wide-Angle Beam Steering at Ka-Band by In-Plane Translation of a Plate Lens Antenna

This paper presents new designs, implementation and experiments of metasurface (MTS) antennas constituted by subwavelength elements printed on a grounded dielectric slab These antennas exploit the interaction between a cylindrical surface wave (SW) wavefront and an anisotropic impedance boundary condition (BC) to produce an almost arbitrary aperture field They are extremely thin and excited by a simple in-plane monopole By tailoring the BC through the shaping of the printed elements, these antennas can be largely customized in terms of beam shape, bandwidth and polarization In this paper, we describe new designs and their implementation and measurements It is experimentally shown for the first time that these antennas can have aperture efficiency up to 70%, a bandwidth up to 30%, they can produce two different direction beams of high-gain and similar beams at two different frequencies, showing performances never reached before

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Metasurface Antennas: New Models, Applications and Realizations

This paper presents a new concept of steerable beam antenna composed by a dielectric lens which pivots in front of a single stationary moderate gain feed. The lens not only allows steering mechanically the beam in elevation and full azimuth, but further increases the gain up to 21 dBi. The solution is broadband, including the entire international unlicensed spectrum from 57 GHz to 66 GHz. A fabricated prototype shows the possibility of tilting the beam from - 45deg to + 45deg for all azimuths with gain scan loss below 1.1 dB and radiation efficiency above 95%. The arrangement is very simple, it does not require rotary joints, it is low cost and compact, lens plus feed volume being of the order of 3 times 3 times 3 cm3 with lens weight less than 10 g.

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Compact Beam-Steerable Lens Antenna for 60-GHz Wireless Communications

This paper presents the theoretical performance (input impedance, -10 dB return-loss bandwidth, radiation patterns and surface efficiencies) of reduced size substrate lenses fed by aperture-coupled microstrip patch antennas. The diameter of the extended hemispherical homogeneous dielectric (/spl epsiv//sub r,lens/) lenses varies between one and five wavelengths in free-space, in order to obtain radiating structures whose directivity is comprised between 10 and 25 dB. A lot of configurations of lenses are investigated using the finite-difference time-domain methods technique and compared in the 47-50 GHz band as a function of their diameter, extension length and dielectric constant. In particular, the analysis of internal reflections-in time and frequency domains-shows that the latter have potentially a strong influence on the input impedance of small lens antennas, even for low values of /spl epsiv//sub r,lens/(2.2), whereas the usual limit (beyond which anti-reflection coatings are required) is /spl epsiv//sub r,lens/=4. We also demonstrate that the diffraction limit of reduced size lenses is reached for extension lengths varying between 50% and 175% of the extension of synthesized ellipses, depending on the lens material and diameter. Finally, we show that superdirective structures with surface efficiencies reaching 250% can be obtained with small lens diameters, justifying the interest in reduced size lens antennas.

Performance of reduced size substrate lens antennas for Millimeter-wave communications

Two new compact lens antenna configurations are presented and compared for data link communications with LEO satellites at 26 GHz These lenses match a secant type radiation pattern template in the elevation plane while having a mechanically scanned sector beam in azimuth to enhance gain as much as possible No rotary joints or multiple feeds are required and emphasis is put also on the compactness of the proposed solutions (< 6lambda0) Two alternative lens configurations are evaluated numerically and experimentally: one is based on modified axial-symmetric dome lens geometry, and the other one consists of a full 3-D double-shell lens antenna In contrast to current nearly omnidirectional antennas, the directivity of our lens prototypes is above 154 dBi Up to 42 dB loss obtained in the prototypes can be significantly reduced by using lower loss dielectrics and matching layers, without affecting the conclusions The numerical and experimental results are in good agreement with the radiation specifications given the compact size of the antennas

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Compact Ka-Band Lens Antennas for LEO Satellites

The purpose of research is to outline the domain of applicability of the geometrical optics (GO) and physical optics (PO) in the small dielectric lens analysis. As a benchmark solution, we use the Muller's boundary integral equations (IE) discretized with trigonometric Galerkin scheme that has guaranteed and fast convergence. The lens cross-section is chosen typical for practical applications, namely an extended hemiellipse whose eccentricity satisfies the GO focusing condition. The lens flat side dimension varies between 2 and 8 wavelengths in free space, and its material is rexolite (s = 2.53). We consider the 2D case with an E-polarized plane wave incidence and extract comparison characteristics from the near field analysis.

Small hemielliptic dielectric lens antenna analysis boundary integral equations vs. GO and PO

A powerful optimization procedure of substrate lens antennas has been proposed at millimeter wave frequencies. Compared to previous works, this approach is global and thus does not require the a priori knowledge of an initial lens profile computed with conventional GO-based synthesis techniques. Our design methodology combines a genetic algorithm with an efficient asymptotic analysis of the radiation characteristics of 3D substrate lens antennas.

A shaping technique of substrate lens antennas with genetic algorithm

This paper compares two different compact lens antenna approaches for a global Earth observation application at 26 GHz. Lens specifications were defined by Alcatel Alenia Space within the framework of ACE Network of Excellence activities. The lenses are required to match a secant square type radiation pattern template in the elevation plane. Two alternative specifications are defined for the azimuth radiation pattern template: either omnidirectional or with a mechanically scanned sector beam to enhance gain. Two alternative lens approaches are also evaluated for the above cases: one based on an axial-symmetric dome lens geometry (developed at "Instituto de Telecomunicacoes", Portugal) and another one based on a fully 3D lens design (developed at "IETR", France).

Gaël Godi

Papers

Performance of reduced size substrate lens antennas for Millimeter-wave communications

Compact Ka-Band Lens Antennas for LEO Satellites

Small hemielliptic dielectric lens antenna analysis boundary integral equations vs. GO and PO

A shaping technique of substrate lens antennas with genetic algorithm

Benchmark of lens antennas for KA-band global earth observation from leo satellites