The self-healing property of Bessel beams (BBs) is used to create a robust wireless link at W-band, maintaining high data rates despite metallic obstructions within their nondiffractive range (NDR). This is demonstrated experimentally using a broadband launcher, which comprises a photonic transmitter and a spline-profile horn, by placing a circular metallic obstacle in the beam’s path. Field measurements show the BB profile remains intact after the obstacle over the 75–105 GHz band. Power transmission tests reveal a record broadband efficiency of up to 70% (-1.54 dB) at 99 GHz across distances of 10 to 30 wavelengths. Bit error rate and real-time communication tests confirm the link’s reliability, achieving error-free data transmission at 3 Gb/s using on-off keying modulation.

This communication describes the bandwidth (BW) characteristics of reflecting Luneburg lenses (RLLs) implemented by a bed of nails (BoN). RLLs' beamformers consist of two vertically stacked parallel-plate waveguides (PPWs) of circular shape. The bottom PPW contains a graded index (GRIN) medium with azimuthal symmetry to address the rays launched by a point source on a focal line along curvilinear paths up to a corner reflector. After reflection and coupling, the rays emerge collimated in the top PPW. The lens' symmetry allows for generating plane waves with arbitrary directions by just changing the azimuthal position of the source in the bottom layer. The use of BoN with higher symmetries helps to synthesize the refractive index profile in the RLL, which also features high values and increases its operational BW by mitigating frequency dispersion. A Ka-band RLL featuring higher symmetries has been fabricated and tested. Simulations and measurements are in good agreement, showing an overall fractional BW of approximate to 39% . This architecture constitutes a metal-only, low-profile beamformer with full azimuthal scanning from 26 to 40 GHz.

This article introduces an all-metal series dual-fed continuous transverse stub (CTS) array that enables multibeam operation at K-band. This capability is obtained using a reflecting Luneburg lens (RLL) beamformer made of two stacked circular parallel plate waveguides (PPWs). The bottom PPW hosts a graded index medium that collimates the rays coupled by a corner reflector to the top PPW, where the CTS array is located. This design capitalizes on the RLL's rotational symmetry, using a circular array of feeds to generate multiple planar wavefronts that illuminate the CTS array across a 360 degrees range. Consequently, a new series-fed CTS array has been introduced to ensure high aperture efficiency when excited from diametrically opposed ends. The appropriate selection of the feeds, combined with the rotation of the CTS plane, enables the generation of simultaneous independent beams with continuous scanning. This architecture enhances the capabilities of conventional variable inclination CTS arrays. A prototype has been fabricated and tested, demonstrating excellent performance between 17.3 and 21.2 GHz, with an aperture efficiency of 43.5%-58% and a radiation efficiency of 90%. The antenna achieves scanning up to 55 degrees in azimuth and from 5 degrees to 65 degrees in elevation through port switching, and full-azimuthal coverage with the added mechanical rotation. This design is particularly significant for K-band low-earth orbit (LEO) high-throughput satellite communications (SATCOMs).

This article presents the design of a dual-lens beamformer in multilayer printed circuit board (PCB) technology. The proposed lens is implemented in a dielectric parallel-plate waveguide (PPW), offering enhanced scanning performances along with a compact design. A combination of ray-tracing and conjugate field matching is used to design the lens and feed configuration. The concept is validated by a prototype operating in the downlink K-band allocated to satellite communications (17.3-20.2GHz). The shaped lens is machined from a stack of substrate layers, while the integrated feed system is realized using standard PCB techniques. The final structure produces nine stable beams over an angular sector of +/- 60 degrees (+/- 10 beamwidths) from a flared linear aperture of about 14 lambda . Good agreement between the simulated and experimental results is obtained. The measured return loss is better than 10dB, and port-to-port isolation is greater than 17dB over the entire frequency band. The estimated radiation efficiency of the antenna is about 75%, and maximum scan losses are in the order of 2dB.

A compact planar beamformer using multiple shaped continuous parallel-plate waveguide delay lenses is proposed in this letter. The original design, based on a single-shaped continuous delay lens, had demonstrated excellent scanning properties over the portion of the $K_{a}$ -band allocated to uplink satcom (27.5–31 GHz). However, its height, due to the transversal ridge and cavity, was limiting its use in more advanced antenna systems. A design methodology is proposed here to achieve similar focusing properties while reducing significantly the beamformer’s height. A specific design is demonstrated with a height reduced by a factor of three when compared to the original design. A reduction of the longitudinal dimension is also proposed by introducing two additional straight ridges and cavities. A prototype was manufactured and tested successfully, with RF performance similar to those of the reference design besides slightly higher insertion losses. This compact design enables to stack multiple lenses to produce two dimensional (2-D) beamforming.

Modulated metasurfaces (MTSs) can be efficiently used to guide the propagation of surface-wave (SW) wavefronts or to gradually radiate the power carried by a SW. These two complementary mechanisms can be applied, respectively, to design beamformers and antennas capable of addressing some of the needs in emerging millimeter wave wireless and future net-works beyond 5G. More precisely, we will present the use of modulated metasurfaces for the design of high-gain antennas and broadband beamformers. We will also show how the later can be efficiently combined with the former to provide multi-beam operation.

This papes describes the application of higher symmetries to enable broadband operation of Reflecting Luneburg lenses (RLL) at Ka-band. RLLs are a new type of beam-former, consisting of two vertically stacked parallel plate waveguides (PPWs) of circular shape, of which the bottom one is filled with a graded index (GRIN) medium with azimuthal symmetry. The rays launched by a source in the bottom PPW follow curvilinear paths such that they emerge collimated in the top PPW after encountering a reflecting boundary. Owing to the lens' symmetry, one can generate plane waves with arbitrary directions by simply changing the azimuthal position of the source in the bottom layer. In this paper, the GRIN medium is implemented by loading the bottom PPW with higher symmetric unit-cells consisting of metallic posts. This solution offers a double benefit: it allows one to synthesize the somehow high refractive indexes in the RLL profile and it also mitigates frequency dispersion, thus increasing the lens operational bandwidth. The proposed architecture constitutes a metal-only, low-profile beam-former that can provide full azimuthal scanning in the whole Ka-band.

Modulated metasurfaces (MTSs) have sprung up in the last decade as an attractive solution for wave guidance and radiation.More precisely, modulated MTS antennas stand out for providing an unprecedented control of the aperture fields with low-profile and lightweight structures.In this class of antennas, a surface-wave (SW) is gradually radiated, owing to its interaction with a modulated impedance boundary condition (IBC).This IBC is typically implemented in the microwave regime by several thousands of sub-wavelength patches printed on a grounded slab.However, dielectric losses may hinder the use of standard printed circuit board (PCB) technology at higher frequencies.In this paper, we will address this issue by introducing a new class of metal-only modulated MTS, which can be easily fabricated by additive manufacturing or micro-machining for millimeter-wave and sub-THz applications.

This paper presents the design of a 19 cm diameter metal-only modulated metasurface (MTS) antenna with right-handed circular polarization (RHCP) at Ka-band, more precisely, in the down-link DSN frequency band. The proposed antenna topology may provide high-gains and can be easily integrated on a CubeSat's chassis. The modulated MTS consists of several thousands of sub-wavelength metallic cylinders, with elliptical cross-sections and different heights and orientations across the aperture. This type of antenna can be easily fabricated by metal additive manufacturing and avoids the problems sometimes encountered by dielectrics in space.

This paper presents the design of a 19 cm diameter metal-only modulated metasurface (MTS) antenna with right-handed circular polarization (RHCP) at Ka-band, more precisely, in the down-link DSN frequency band. The proposed antenna topology may provide high-gains and can be easily integrated on a CubeSat’s chassis. The modulated MTS consists of several thousands of sub-wavelength metallic cylinders, with elliptical cross-sections and different heights and orientations across the aperture. This type of antenna can be easily fabricated by metal additive manufacturing and avoids the problems sometimes encountered by dielectrics in space.

Perfectly wrapping planar electronics to complex 3D surfaces represents a major challenge in the manufacture of conformable electronics. Intuitively, thinner electronics are easier to conform to curved surfaces but they usually require a supporting substrate for handling. The water transfer printing (WTP) technology utilizes water surface tension to keep ultrathin electronics floating flat without supporting substrate, enabling their conformal transfer on 3D surfaces through a dipping process. In many cases, however, the size of the microfabricated electronics is much smaller than the target 3D surface. This work proposes that such mismatch in size can be overcome by leveraging stretchable electronics in WTP. Stretchable electronics are compliant to in-plane stretch induced by water surface tension, hence can first self-expand in water and then be transferred onto 3D objects. Uniaxial and biaxial expansion ranging from 41% to 166% has been achieved without any externally applied tension. The results demonstrate that expansion-enhanced WTP is a promising fabrication process for conformable electronics on large 3D surfaces.

In this paper, shaped continuous parallel plate waveguide delay lenses are proposed. The previous configurations introduced by the authors displayed a residual side lobe imbalance, showing the limitations of elliptical delay lens profiles, derived from a starting bifocal constrained lens. Polynomial profiles are proposed here as a way to enhance the scanning performance and the pattern shape. Optimized configurations demonstrate a reduction in the phase aberration levels over a large scanning range ([-30, 30]). The associated radiation patterns demonstrate lower and more balanced first side lobe levels (SLLs) ( $\cong -18$ dB), as compared to the previous elliptical approach ( $\cong -13.2$ dB). A validation has been proposed through the manufacturing and test of a prototype over the down-link Ka-band ([27.5-31] GHz). Excellent radiation performance [half-power beamwidth (HPBW), SLL] has been experimentally obtained over a wide angular range ([-31.5, 31.5]), including low scanning loss and high radiation stability over the entire frequency range. High radiation efficiencies are demonstrated with this fully metallic design, particularly suitable for space applications. The mechanical simplicity offered by the concept is also quite attractive for low-cost multi-beam platforms.

In metasurface (MTS) antennas, a surface-wave (SW) is gradually radiated by modulating an equivalent reactance tensor in the aperture plane. Such modulation results in the (−1) indexed Floquet mode entering the visible region, thus becoming a leaky-wave (LW) mode with curvilinear phase-contour. This paper explores the use of a class of metallic MTS in the synthesis of the reactance tensor required to obtain the objective radiation patterns. The absence of dielectric is useful to survive harsh environments in space exploration. The proposed element consists of a metallic cylinder with elliptical cross-section, placed on a ground plane and arranged in a square lattice with sub-wavelength unit-cell side. We have applied this structure in the design of a right-handed circularly polarized antenna, with a broadside pencil beam in the Ka band. The obtained performance has been verified by full-wave simulations. A prototype has been manufactured and measurements will be available at the time of the conference.