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International audience; We present the design and experimental validation of wideband dual-circularly-polarized (dual-CP) reflect-arrays (RAs) based on dual-functional-layered unit cells with independent control of circular polarizations. The proposed dual-CP RA cells comprise a circular polarization selective surface (CPSS) on the top based on a bandwidth-enhanced dual-meandered Pierrot structure that implements polarization selection of CP waves and a reflective half-wave plate (HWP) on the bottom. The dual-CP phase delay of the RA cells relies on the Berry-phase (BP) dictated by the rotation of the CPSS and HWP elements for achieving reflective beamforming of CP waves of opposite handedness. The diffractive properties of an infinite periodic gradient array of the dual-CP RA cells in a triangular lattice are investigated, which numerically verifies the dual-CP anomalous reflection capability. Two proof-of-concept RAs operating at X-band are designed, fabricated, and characterized. By replacing only the bottom functional layer of the RA, symmetrical and asymmetrically distributed dual-CP beams can be obtained. A measured peak gain of higher than 23.5 dBic is achieved, with a joint bandwidth of 11% for an axial ratio < 2 dB and a gain variation < 1 dB. The improved bandwidth performance, high-resolution BP compensation, and printed manufacturing process without using any metallic cavities make the demonstrated CPSS-based dual-CP RAs promising candidates for wireless and satellite communications.

As a prominent candidate to cope with both device integration and miniaturization, multifunctional metadevices have attracted increasing interest recently. However, suffering from several demerits, conventional multifunctional devices that could not meet practical demands. In this paper, we elaborate on a single-layer transmissive all-dielectric meta-lens platform that can flexibly manipulate beams by pluggable phase elements over a broad millimeter-wave regime. The pluggable element of the meta-lens platform is able to provide a full 2π transmission phase coverage together with a high transmission coefficient. The elements are encoded into 36 phase modules as a phase library. The designed phase modules can be re-assembled that span 2π uniformly to reconstruct distinct functions, due to their dynamic pluggable feature. To verify its flexible assembly and efficient phase modulation, the meta-lens platform with different arrangements of phase modules is assembled and demonstrated in the experiment, which is in good agreement with theoretical and simulation analyses. Owing to the properties of flexible assembly, broad bandwidth, and high efficiency, the proposed meta-lens platform paves the way for potential applications in millimeter-wave regimes such as beamforming, computer-generated hologram, and other complex demands that involve phase manipulations.

International audience; In this letter, a dual-circularly polarized (dual-CP) multibeam transmit-array (TA) antenna is proposed and demonstrated based on anisotropic impedance surfaces (AISs) and hybrid phase compensation strategy. A set of eight fully planarized TA cells based on cascaded AISs are designed with a constant dynamic phase difference between each other, possessing a periodicity of 0.48λ0 × 0.48λ0 and a total thickness of 0.71λ0, where λ0 is the free-space wavelength at center frequency. By introducing Berry phase determined rotation angles on the eight designed cells, dual-CP transmissive phase delays can be achieved independently. Moreover, planar dual-CP antenna arrays are designed and utilized as the feed cluster of the multibeam TA. The bifocal dual-CP multibeam TA antenna generates eight RHCP beams and eight LHCP beams. The measured peak gain values are between 21.1 and 23.7 dBic, whereas the AR values are all below 3 dB for all the beams. © 2002-2011 IEEE.

In this article, the theory, design, and demonstration of wideband and low-profile dual-circularly polarized (dual-CP) transmit arrays (TAs) are reported, which support independent beamforming for left-/right-handed CP waves. This is achieved by utilizing an antenna–filter–antenna configuration for the TA unit cells with a profile of only about $0.11\lambda _{0}$ , which consists of receiving and transmitting stacked patches connected by two microstrip delay lines. By utilizing the phase delay lines and unit cell rotation, the dynamic phase and the Berry phase can be simultaneously exploited for providing continuous dual-CP transmissive phase compensation insensitive to the angle of incidence. The diffraction analysis of a linear gradient array of the proposed cells confirms its wideband performance of abnormal refraction. In addition, broadband CP planar feed arrays were designed and verified for functioning as low-profile feeds with symmetrical patterns for the TAs. As proof-of-concept examples, two $K$ -band dual-CP TAs integrated with the planar feeds were synthesized, fabricated, and measured, possessing a total profile of about $7.1\lambda _{0}$ . The two prototypes offer either symmetrical or asymmetrical dual-CP beams over a wide bandwidth. Their measured peak gain is higher than 22 dBic, while the joint $S_{11} dB, axial ratio < 2 dB, beam squinting

In this article, a compact triple-port dual-band triple-mode antenna enabled by a shielded mushroom structure with operational bands centered at 2.4 and 5.8 GHz is proposed possessing both pattern and polarization diversities. By tailoring the dispersive properties of the artificial transmission line (ATL) cells and structuring them into a multilayer architecture, the integrated antenna is capable of generating vertically polarized, $y$ -horizontally polarized, and $x$ -horizontally polarized radiation patterns simultaneously at two predefined bands with good port isolations and field orthogonality. The design concept and the analysis of the ATL cells in the form of shielded mushrooms are described, illustrating the dual-band operating principle of the antenna. A proof-of-concept antenna is designed with a footprint of $0.48\lambda _{0}^{2}$ and a profile of $0.07\lambda _{0}$ , where $\lambda _{0}$ is the free space wavelength at 2.4 GHz. The proposed antenna was fabricated and characterized, achieving measured $S_{11} dB bandwidths of 35 and 85 MHz in the two targeted bands, respectively, with mutual coupling smaller than −15 dB and envelope correlation coefficients below 0.01 for all three ports. Moreover, it is shown that the two operational bands of the antenna can be independently controlled, which reveals the unprecedented degrees-of-freedom in its design. The demonstrated dual-band triple-mode antenna is highly useful for dual-band multimode wireless devices and dual-band multiple-input multiple-out communication systems.

A low-profile, broadband, dual-linearly polarized (dual-LP), and wide-angle millimeter-wave antenna array with beam-steerable capabilities operating in the Ka -band is proposed for 5G applications. By jointly exploiting miniaturized vertically stacked elliptical patches, orthogonal aperture-coupled stripline feeding structures, and groups of shorting pins loaded close to the coupling apertures, the proposed dual-LP element has a small footprint of 4.5 × 4.5 mm with a total thickness of 1.57 mm, which exhibits a measured −10 dB impedance bandwidth of 21.8% and a mutual coupling below −41 dB. Wideband stripline-based Butler matrix circuits are designed and integrated with the 1 × 4 element array for verifying its broadband dual-LP multibeam radiation performance. Experimentally, the integrated array generates four beams with an angular coverage of about ±61° and ±75° for x - and y -polarizations, revealing that the proposed array is a promising candidate for 5G applications.

A circularly polarized (CP) reflectarray with 2-D electronically steerable beam is reported. The reconfigurable CP reflectarray element is realized using a circular-patch-based structure with p-i-n diodes incorporated. A new electronical phase manipulation method is proposed based on the element rotation technique and by additionally exploiting symmetries in the field distribution of the element’s fundamental resonant mode. Element rotation can be equivalently achieved by altering the biasing voltage and changing the electromagnetic behavior of the reflective phasing cell. The proposed design approach brings about simplification in element configuration, leading to a reduction in the number of required diodes by a factor of one half. Practical concerns of the element and biasing complexity as well as the insertion loss are, therefore, well-handled. A fully functional $16\times16$ reconfigurable CP reflectarray is designed, fabricated, and tested to validate the concept. Good beam focusing and 2-D dynamic beam steering capabilities are confirmed through experiments, along with decent polarization purity and comparatively high aperture efficiency. The proposed simple and robust design could be attractive for implementing lightweight, low-cost, and large-scale 2-D reconfigurable CP reflectarrays.

Identifying, quantifying, and suppressing decoherence mechanisms in qubits are important steps towards the goal of engineering a quantum computer or simulator. Superconducting circuits offer flexibility in qubit design; however, their performance is adversely affected by quasiparticles (broken Cooper pairs). Developing a quasiparticle mitigation strategy compatible with scalable, high-coherence devices is therefore highly desirable. Here we experimentally demonstrate how to control quasiparticle generation by downsizing the qubit, capping it with a metallic cover, and equipping it with suitable quasiparticle traps. Using a flip-chip design, we shape the electromagnetic environment of the qubit above the superconducting gap, inhibiting quasiparticle poisoning. Our findings support the hypothesis that quasiparticle generation is dominated by the breaking of Cooper pairs at the junction, as a result of photon absorption by the antenna-like qubit structure. We achieve record low charge-parity switching rate (

International audience; We report here the design and experiments of dual-wideband dual-circularly-polarized (dual-CP) shared-aperture reflectarrays (RAs) operating at K-/Ka-band utilizing a single functional substrate. By coupling the adjacent but separated resonances of H-shaped aperture and circular patch and utilizing the shorted microstrip phase delay lines, the proposed RA cells can offer wideband performance. Then, these RA cells are interleaved in a shared aperture for dual-band operation. By combining the dynamic phase and Berry phase compensation techniques, the RA cells can independently control the reflective phase delay of orthogonal CP beams at both of the targeted bands, providing four degrees of freedom for beamforming. The diffractive property of an infinite periodic gradient array of the interleaved K- and Ka-band cells is investigated, which verifies the wideband performance of the proposed cells. Two RAs with a thin panel thickness of 0.27 and#x03BB;K (and#x03BB;K is the free-space wavelength at K-band) are fabricated and characterized, generating symmetrically- and asymmetrically-distributed dual-wideband dual-CP beams at K-/Ka-band, respectively. The measured bandwidths for the two RAs are wider than 14.1% for K-band right-/left-handed CP beams and about 11% for Ka-band right-/left-handed CP beams with both the gain variation and axial ratio smaller than 2 dB.

In this article, a self-calibration method for 5G full-digital time-division duplexing (TDD) beamforming systems is proposed and demonstrated, including the self-calibration for both the transmit (Tx) and receive (Rx) channels. By incorporating an embedded transmission line (ETL) in the antenna array that weakly couples with all the radiating elements, the relative magnitude and phase of each Tx/Rx channel can be obtained with the proposed calibration procedure. Comparing with conventional self-calibration methods, the proposed approach requires simpler hardware and reduced calibration time. As a proof-of-concept example, a $1\times 8$ full-digital TDD beamforming array operating at 3.5 GHz with an ETL is fabricated for validation. To further evaluate the accuracy of the calibration data, the “stepped null” calibration was conducted by the over-the-air (OTA) measurement. It is shown that the root mean square (rms) phase and magnitude errors of the calibration results for the Tx and Rx channels are 5.8°/0.84 and 6.3°/0.91 dB, respectively, which are sufficiently accurate for beamforming in 5G communication systems.

A hybrid analog–digital multibeam antenna array (MBAA) consisting of two types of 1-D beamformers for two orthogonal planes, respectively, is proposed for massive multiple-input multiple-output (MIMO) communication systems at millimeter-waves. In the vertical direction, the multiple beams are generated by a passive beamformer, i.e., a Butler matrix, whereas the multibeam coverage in the horizontal plane is achieved digitally at the baseband. Comparing to a full-digital multibeam array, the digital beamforming (DBF) processing is simplified in the proposed scheme, significantly alleviating the computational burden of data processing. Since the radiation beams are generated by only a part of the radio frequency (RF) channels in the hybrid multibeam array, the power consumption could be reduced by powering down the idle channels. To verify the concept, a two-dimensional (2-D) array comprised by 16 columns of eight-beam tapered slot antenna subarrays is designed and fabricated, in which each subarray contains a pair of $4 \times 8$ modified Butler matrices based on the substrate-integrated waveguide technology. The measured results exhibit that the operating bandwidth is 13.45% for the subarray fed by the modified Butler matrices implemented by substrate-integrated waveguides. The RF receivers, intermediate frequency (IF) chains, and analog-to-digital converters (ADCs) are also implemented to enable the DBF in the horizontal plane. The maximum simulated directivity of the array is 27 dBi. A wide 2-D spatial angle is covered simultaneously by the proposed hybrid passive-DBF scheme. The demonstrated 2-D millimeter-wave hybrid array may find widespread potential applications in future communication systems.

In this article, the theory, design, and validation of planar array antennas capable of producing dual-circularly-polarized (dual-CP) dual-beam radiation with a single feeding network are reported. Importantly, the properties of the formed CP beams with different handedness can be independently controlled. Such a capability is achieved by exploiting both the in-plane rotation-induced Berry phase and excitation phase for all the linearly polarized array elements, which can be regarded as a generalization of the well-known sequential rotation arrays. Microstrip patch arrays with such single-feed dual-CP dual-beam functionalities can be synthesized through a straightforward analytical approach that accurately predicts the radiation patterns for both right- and left-handed CP beams. The proposed technique and design methodology were verified by two proof-of-concept microstrip arrays consisting of $8 \times 8$ linearly polarized circular patch elements operating in the $K$ -band, one with uniform excitation amplitudes and the other with tapered excitations for sidelobe suppression. Both arrays were fabricated and measured, experimentally achieving a joint $S_{11} dB, axial ratio < 3 dB, and 3 dB gain bandwidth of more than 22.5%/20.0% and 16.7%/15.8%, respectively, for the right- and left-handed CP beams. Within this broad operational band, the beam squinting is on average within ±3°. The proposed dual-CP dual-beam arrays have fully planarized structures, low profiles, wide operational bandwidths, and high polarization purity, making them useful candidates for applications including satellite communications, point-to-multipoint communications, and so on.

In this work, compact polarization-controllable dual-band antennas are designed, prototyped, and experimentally verified, which are composed of a planar monopole on top of a dual-layer truncated metasurface (MS) containing patches and nonbianisotropic complementary split ring resonators. By tailoring the dispersive properties of the MS, the relative phase difference of resonances associated with surface waves supported along two orthogonal horizontal directions can be independently engineered at two separate frequency bands, thereby giving rise to compact dual-band antennas with controllable polarization in each band. Three proof-of-concept example antennas with a form factor on the order of $0.3\lambda _{\mathbf {0}}\times 0.3 \lambda _{\mathbf {0}} \times 0.04 \lambda _{\mathbf {0}}$ were designed and measured. The first one provides circularly polarized (CP) radiation with the same sense of polarization in both bands, the second one offers linearly polarized (LP) radiation in the lower band and CP radiation in the higher band, while the last one achieves CP radiation in the lower band and LP radiation in the higher band. The measured results agree well with the simulation predictions, thus verifying the proposed concept and specific antenna designs.

Ever since the deployment of the first-generation of mobile telecommunications, wireless communication technology has evolved at a dramatically fast pace over the past four decades. The upcoming fifth-generation (5G) holds a great promise in providing an ultra-fast data rate, a very low latency, and a significantly improved spectral efficiency by exploiting the millimeter-wave spectrum for the first time in mobile communication infrastructures. In the years beyond 2030, newly emerged data-hungry applications and the greatly expanded wireless network will call for the sixth-generation (6G) communication that represents a significant upgrade from the 5G network - covering almost the entire surface of the earth and the near outer space. In both the 5G and future 6G networks, millimeter-wave technologies will play an important role in accomplishing the envisioned network performance and communication tasks. In this paper, the relevant millimeter-wave enabling technologies are reviewed: they include the recent developments on the system architectures of active beamforming arrays, beamforming integrated circuits, antennas for base stations and user terminals, system measurement and calibration, and channel characterization. The requirements of each part for future 6G communications are also briefly discussed.

This letter reports a strategy of full-digital arrays with nonreciprocal transmitting (Tx) and receiving (Rx) beam patterns, for the first time, for 5G/6G wireless communications. The proposed full-digital array contains a smaller number of Rx channels than that of the Tx channels. The unequal number of Tx and Rx channels makes the transmitting and receiving patterns asymmetrical, which would not only release the burden of data processing but also reduce the hardware cost and power consumption of the entire system. Importantly, as compared with conventional large-scale beamforming arrays, the proposed strategy will not deteriorate the range of coverage at an instantaneous time. A 64-element full-digital beamforming array prototype was designed, fabricated, and characterized for a proof-of-concept demonstration.

In this article, a novel beamforming patch array with a cosecant fourth power pattern is proposed for millimeter-wave synthetic aperture radar (SAR) applications. It enables radar receiving identical power in the field of view, provided that the radar cross section levels of targets within the illuminated area are similar. Different from “one-way” communication application, the SAR is a “two-way” system such that the received power is inversely proportional to $R^{4}$ , not $R^{2}$ , where $R$ is the distance between target and radar. Thus, conventional cosecant squared patterns are not suitable for SAR. Here, the concept and link properties of the proposed cosecant fourth power pattern are introduced, while its synthesis process is facilitated by a mixed optimization method, including nonlinear fitting and active pattern methods. As demonstrated, an array prototype, which consists of 12 series-fed patch subarrays and a substrate integrated waveguide network for power distributing and phase shifting, is designed and fabricated. Particularly, the power-distributing section only consists of symmetrical T-junctions with equal power division, thus making the antenna more tolerant to fabrication error. Good cosecant fourth pattern performance is achieved from 23.8 to 25.0 GHz. The presented array also owns the advantage of low profile ( $\sim 0.09\lambda _{0}$ ), compact, reliable, and low cost.

A low-cost millimeter-wave circularly polarized (CP) planar integrated magneto-electric dipole (ME-dipole) element with simple structure is proposed, which is fed by a low-profile feeding structure capable of being directly integrated with Ka -band front-end circuits. Two rotationally symmetrical L-shaped patches are adopted to replace the two straight arms of the original linearly polarized ME-dipole to generate a rotated electric field, thus radiating CP waves. Based on this CP ME-dipole element, CP array antennas containing 2 × 2 and 4 × 4 radiators with low-profile full-corporate feeding networks are developed without any additional dielectric layer. Prototypes of these two CP array antennas are fabricated and measured. Good agreement between the simulated and measured results is achieved, validating the correctness of these two designs. The 2 × 2 array exhibits a | S 11| Ka -band satellite communications, etc.

We present the modeling, design, and experiments of a class of low-profile and broadband dual-circularly polarized (DCP) reflectarrays (RAs) with independent beamforming for CP waves with opposite handedness. The proposed DCP RAs are comprised by an array of unit cells containing two cascaded anisotropic impedance surfaces backed by a ground plane. The DCP phase compensation offered by the RA cells is enabled by simultaneously utilizing cell rotation-induced Berry phase and dimension variation-induced dynamic phase. Numerical investigations of the diffraction properties of a linear gradient array of the DCP cells reveal that the designed cells can offer independent and high-efficiency deflection of CP waves with opposite handedness over a bandwidth of about 40%. Two Ka -band DCP RAs with a profile of only $0.16\lambda _{0} $ are demonstrated. The single-beam DCP RA achieves a measured peak gain of higher than 30 dBic with a joint 1 dB gain and axial ratio < 0.5 dB bandwidth of around 30%, while the multibeam DCP RA exhibits a measured peak gain of about 26 dBic with a joint 1 dB gain and axial ratio < 1.5 dB bandwidth of more than 25%. The demonstrated broadband DCP RAs are promising candidates for various wireless and satellite communication systems.

In this article, the Babinet principle is applied for complementary periodic sub wavelength metallic elements $A^{e}$ and $A^{c}$ at the interface between different substrates. For the problem, the restriction of the Babinet principle is mainly resulted from the inhomogeneity of the different substrates or the anisotropy of the metallic elements. In order to break the restriction, a virtual substrate with an effective permittivity is inserted into the interface to cover $A^{e}$ and $A^{c}$ as an updated physical boundary condition. As the thickness of such a virtual effective substrate layer approaches zero, the updated model will not only remain the same as the original one for $A^{e}$ and $A^{c}$ but also can be solved by the existing Babinet principle with a feasible mathematical method. Finally, according to the network transmission theory and Babinet principle, the proposed theory gives the specific mathematical relationship between the tangential transmission matrices of $A^{e}$ and $A^{c}$ . Two examples are simulated to verify the theory, regardless of the substrate, metallic elements, and incidence angle. This method not only greatly simplifies the solutions of complementary metasurfaces but also shows higher precision than the previous work.

Polarization manipulation plays an important role in real applications. In this article, full polarization transformation using graphene has been first achieved in microwave frequencies. Without the aid of lumped elements like varactors or p-i-n diodes and without changing the geometrical parameters of the structure, the polarization conversion such as linear to linear, linear to circular, and linear to elliptical can be realized simultaneously by only changing the sheet resistance of graphene. Furthermore, based on the transmission line (TL) model, the relationship between polarization states and different sheet resistance of graphene has been investigated in detail. Four prototypes have been fabricated based on the chemical vapor deposition (CVD) -grown graphene, which has the desired sheet resistance of 10, 150, 300, and $1000~\Omega $ /sq. Both the full-wave simulated results and measured results demonstrate that our structures can efficiently perform the function of polarization transformation by varying the sheet resistance of graphene, which reveal that graphene has great potential for microwave manipulation.

In this article, a low-profile and wideband triple-port printed antenna for wireless body area network (WBAN) on-body and off-body communications is presented. Three ports are responsible for exciting three different patterns that are orthogonal to each other, including a vertically polarized omnidirectional pattern and two horizontally polarized broadside patterns with radiated fields polarized along the x- and ${y}$ -directions, respectively. In particular, the vertically polarized pattern is achieved by loading an annular array of metallic vias connected to a pin-fed patch antenna on the bottom, while the horizontally polarized patterns are enabled by a closely spaced modified E-shaped stacked patch on the top with additional slot cuts. The integrated antenna was fabricated and characterized, achieving a measured wide $S_{11} dB bandwidth of nearly 14%, a mutual coupling smaller than −15 dB, and an envelope correlation coefficient of less than 0.01. Further numerical and experimental investigations reveal that the proposed antenna has robust electrical properties under both structural deformation and human body loading. The superior performance indicates that the demonstrated antenna is a promising candidate for WBAN devices that can simultaneously support multiple communication modes as well as for other MIMO communications and sensing systems.