Holographic Antenna Research Articles

A Small-Aperture and High-Performance Endfire Holographic Antenna Based on Spoof Surface Plasmon Polaritons

A Small-Aperture and High-Performance Endfire Holographic Antenna Based on Spoof Surface Plasmon Polaritons

Highly efficient meta-lens integrated holographic surface antenna

We demonstrate the generation of highly directive circularly polarized beams by proposing a meta-lens to calibrate the near fields over the holographic surface. Such a design possesses the merits of ultra-low profile as a lens system on the basis of phase compensation of a specific radiating aperture rather than the conventional consideration of the lens focus, and the ratio between the overall height of the antenna architecture and diameter of radiating aperture is only 0.09. Especially, the proposed meta-lens integrated holographic surface also offers a satisfactory solution to improve the overall efficiency of holographic antennas, and the experimental results verify the proposed design with 27.6 dBic measured gain and 40.4 % aperture efficiency at 15 GHz. We expect the proposed strategy of integrating phase compensation lens closely over the holographic surface, pave the way for highly efficient meta-radiators with ultra-low profile.

Beamforming Inferring by Conditional WGAN-GP for Holographic Antenna Arrays

Beamforming Inferring by Conditional WGAN-GP for Holographic Antenna Arrays

Double-Layer Cross-Embedded Holographic Antennas With Compact Size and High Efficiency

Double-Layer Cross-Embedded Holographic Antennas With Compact Size and High Efficiency

Nonuniform Modulated Holographic Antenna With Wide Gain Bandwidth and Scanning Angle

Nonuniform Modulated Holographic Antenna With Wide Gain Bandwidth and Scanning Angle

Compact and Highly Isolated Continuous Scanning Dual-Polarized Holographic Antenna Using a Pillbox Feeding Structure

In this paper, we propose a novel approach to realize a compact and highly isolated dual-polarized holographic antenna using a pillbox feeding structure. The proposed antenna feeds dual orthogonal surface waves with low distortion phase distribution and high isolation through a compact three-layer pillbox feeding structure. This antenna also consists of a shared aperture dual-polarized hologram pattern calculated to radiate the objective wave in the desired direction without increasing the antenna size. As a result, the proposed holographic antennas (HA) have a compact size and support forward-to-backward continuous scanning with minimal gain degradation. The simulated and measured results are in good agreement, validating the efficiency of the proposed antenna design, which has the ability to scan the beam direction from +18° to −25°, passing through the broadside within the frequency range of 21–27 GHz. Finally, the proposed antenna has a broadside gain of 18.5 dBi in each polarization and a gain variation of less than 2 dB within the operating bandwidth.

Tensor-Free Holographic Metasurface Leaky-Wave Multi-Beam Antennas with Tailorable Gain and Polarization.

Recently, the community has seen a rise in interest and development regarding holographic antennas. The planar hologram is made of subwavelength metal patches printed on a grounded dielectric board, constituting flat metasurfaces. When a known reference wave is launched, the hologram produces a pencil beam towards a prescribed direction. Most earlier works on such antennas have considered only a single beam. For the few later ones that studied multiple beams, they were achieved either by having each beam taken care of by a distinct frequency or by partitioning the hologram, thereby depriving each beam of the directivity it could have had it not shared the holographic aperture with other beams. There have been recent studies related to the use of tensor surface impedance concepts for the synthesis of holograms which have attained control over the polarizations and intensities of the beams. However, this approach is complicated, tedious, and time-consuming. In this paper, we present a method for designing a planar holographic leaky-wave multi-beam metasurface antenna, of which each simultaneous beam radiating at the same frequency towards any designated direction has a tailorable amplitude, phase, and polarization, all without hologram partitioning. Most importantly, this antenna is exempted from the need for the cumbersome technique of tensor impedance. Such features of beam configurability are useful in selective multiple-target applications that require differential gain and polarization control among the various beams. Only a single source is needed, which is another benefit. In addition, effective methods to mitigate sidelobes are also proposed here. Designs by simulations according to the method are herein validated with measurements performed on fabricated prototypes.

Improving Impedance Calculations for Cylindrical Conformal Holographic Antenna With a Small Radius

Improving Impedance Calculations for Cylindrical Conformal Holographic Antenna With a Small Radius

Compact Holographic Antenna for Continuous Backward-to-Forward Scanning With Low Cross Polarization Using Anisotropic Cells

Compact Holographic Antenna for Continuous Backward-to-Forward Scanning With Low Cross Polarization Using Anisotropic Cells

Low-profile Circularly Polarized Dual-beam Holographic Antenna

Low-profile Circularly Polarized Dual-beam Holographic Antenna

Non-linear least squares optimization for the design of low side lobe level bidirectional holographic antennas

In this manuscript, an analytical framework aimed at optimizing the performance of double-sided modulated metasurface antennas featuring independent beams is introduced. To synthesize the aperture field distribution, the proposed framework employs the adiabatic Floquet-wave expansion technique as the analysis strategy and the aperture field estimation method as the synthesis technique. For the modulation index, the nonuniform distribution with unknown coefficients is chosen to improve the side lobe level. The ideal values for each of these unknown coefficients are obtained using a non-linear least squares approach. The obtained results demonstrate the efficiency of the proposed methodology for both vortex and pencil beams. To illustrate its feasibility, a double-sided hologram is designed, radiating a pencil beam and a vortex beam on each side.

THz quad-beam holographic antenna with independent beam control and low sidelobe levels

THz quad-beam holographic antenna with independent beam control and low sidelobe levels

Deep-learning-assisted reconfigurable metasurface antenna for real-time holographic beam steering

Abstract We propose a metasurface antenna capable of real-time holographic beam steering. An array of reconfigurable dipoles can generate on-demand far-field patterns of radiation through the specific encoding of meta-atomic states i.e., the configuration of each dipole. Suitable states for the generation of the desired patterns can be identified using iteration, but this is very slow and needs to be done for each far-field pattern. Here, we present a deep-learning-based method for the control of a metasurface antenna with point dipole elements that vary in their state using dipole polarizability. Instead of iteration, we adopt a deep learning algorithm that combines an autoencoder with an electromagnetic scattering equation to determine the states required for a target far-field pattern in real-time. The scattering equation from Born approximation is used as the decoder in training the neural network, and analytic Green’s function calculation is used to check the validity of Born approximation. Our learning-based algorithm requires a computing time of within 200 μs to determine the meta-atomic states, thus enabling the real-time operation of a holographic antenna.

Flat-Topped Radiation Pattern Synthesis of a Conformal Leaky-Wave Holographic Antenna

A novel method to synthesize a flat-topped pattern in single-curvature conformal leaky-wave antennas (CLWAs) is presented. When synthesizing the antenna, aperture field estimation (AFE), the holographic principle, the transformation optic (TO) approach, and the effects of the geometrical parameters of a curved structure on the far-field radiation pattern are considered. In the design process, three software packages (HFSS, MATLAB, and CST) are used to achieve the desired far-field radiation pattern at the design frequency. The shaped beam is in the broadside direction at 10 GHz. This CLWA is composed of unit cells with square patches that are printed on a double-layer grounded substrate which consists of PLA (Polylactic Acid) and Rogers RO4003 having thicknesses of 4 mm and 0.127 mm, respectively. An edge-fed 1:8 power divider excitation with a substrate integrated waveguide (SIW) structure is designed to illuminate the hologram. The proposed CLWA is fabricated and tested. The maximum realized gain of the novel antenna at the design frequency is about 13 dBi, and the weighted aperture efficiency of the proposed CLWA is about 0.86. There are also good agreements between the simulation and the measurement results of the proposed antenna frequency responses.

Angle-Dependent Synthesis Method for Holographic Multi-Feed Antennas

A novel synthesis method for holographic multi-feed antennas is presented to combine all sub-holograms into an angle-dependent shared holographic aperture. In order to find the global error minimum between the shared holographic aperture and all ideal sub-holograms, a non-pixel-based genetic optimization is used. For a more accurately implementation of the analytical impedance tensor an eigenvector approach taking all tensor components into account is introduced. The optimized holographic antenna has four feeds for an exemplary integration into a 2D-monopulse radar system and is realized on a fused silica wafer due to its lower loss at millimeter-wave frequencies compared to Teflon-based materials. The antenna prototype provides a measured gain of 23 dBi, a polarization purity of 26and a side-lobe level of 20for feed 1, 2 and 4 is reached across 76–81. The S-parameters are measured from 60to 90, and a reflection coefficient of –14and an inter-port coupling <–38are achieved. The measured 2D-monopulse patterns provide a FOV of 10, the sum beam has a gain of 26 dBi leading to an aperture efficiency of 45and the differential beams show a null depth of 30.

A Low-Profile Programmable Beam Scanning Holographic Array Antenna Without Phase Shifters

Beam scanning antenna brings new opportunities to reduce the data collision of multinode communication in the Internet of Things (IoT). This article proposes a new type antenna design scheme that can be used for IoT relay communication. A programmable beam scanning antenna without phase shifters operating in the X-band is designed to evaluate the feasibility of this scheme. The integrated design of excitation source and phase-modulated structure greatly reduces the profile of the antenna and improves the integrated degrees of freedom with other equipment. By switching the state of the PIN diode loaded on each element, different radiators can be selected and the direction of current polarization on elements can be adjusted to change the radiation phase. Furthermore, the diode states are encoded by the holographic antenna theory and controlled by the FPGA controller to realize programmable beam scanning. One-element, two-element, and 1-D array containing 32 elements are fabricated and measured. The experimental results are in good agreement with the simulation data. The operating bandwidth is 7.5% at 10 GHz while the beam scanning range of the array is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$- 60{^\circ }$ </tex-math></inline-formula> –60°, with a good scanning accuracy and stability. The proposed low-profile beam scanning antenna can provide stable communication services to multiple users and smart devices as a new type of beam scanning array antenna solution for the IoT application, which is beneficial to this field.

Performance Improvement of LC-Based Beam-Steering Leaky-Wave Holographic Antenna Using Decoupling Structure

A liquid crystal-based beam-steering leaky-wave holographic antenna is designed with decoupling structure. Since the distance between elements in holographic antennas is inevitably small ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ &lt; \!\!\!\lambda $ </tex-math></inline-formula> /5), the mutual coupling is strong and should be compensated for the accurate implementation of the excitation amplitude and phase of each element. The performance degradation of a holographic antenna due to mutual coupling is estimated and a decoupling structure is proposed, fabricated, and inserted into the designed antenna. The operating principle of the decoupling structure is explained with circuit model and the simulation confirms the enhanced gain and sidelobe performance when steered from −60° to 60° in 20° intervals. Compared to the antenna without the decoupling structure, the maximum improvement of the gain and the sidelobe level is 3.93 and 7.7 dB, respectively, in the simulation. The experimental results are consistent with the simulation results.

Graphene Based Tunable Terahertz Holographic Antennas

In this work, several representative terahertz (THz) graphene holographic impedance surface antenna are presented. Different to the conventional impedance surface antenna that manipulates the surface impedance via varying the patch size in each unit cell, the surface impedance of the proposed antenna in this paper is readily controlled by applying a tunable DC biasing to each graphene patch cell, the physics behind which is that the conductivity of the graphene is a function of imposed voltage. Thus, the graphene patches of the proposed antenna have same size as well as equal spacing, which makes the modeling process more convenient and efficient. Furthermore, for the purpose of beam scanning, the proposed THz graphene holographic antenna can be easily reached by varying the DC supply. Besides, due to the excellent mechanical property of graphene, the proposed THz graphene holographic antenna can be designed conformal to required platforms. To validate and verify the proposed above ideas, a linear polarized with beam scanning capability, a circularized and a conformal THz graphene holographic antenna are designed and simulated via full-wave commercial software HFSS, the simulation results are in good agreements with the design theories.

A wideband low‐radar cross section circularly polarized holographic antenna based on hybrid metasurface

A wideband low‐radar cross section circularly polarized holographic antenna based on hybrid metasurface

Improved performance of an axially-modulated conformal leaky-wave holographic antenna through using variable modulation index

In this paper, a novel method to decrease the sidelobe level (SLL) of conformal leaky-wave antennas (CLWAs) which are synthesized based on the holographic techniques is proposed. For this purpose, the holographic relation is modified by using the modulation index as a function of the spatial component corresponding to the propagation direction of the reference wave. In order to create a fascinating impedance matching between the launcher and the radiative metasurface, an initial phase is considered in the holographic formula. The designed one-dimensional (1D) sinusoidally modulated conformal antenna indicated a broadside fan beam at 18 GHz. At this frequency, about 3 dB SLL reduction was observed in the E-plane compared the traditinal holographic antenna. The measurement results indicated that the realized gain of the novel antenna at the design frequency was about 14.6dBi, and the SLL and the radiation efficiency of the antenna were −10.6 dB and 95%, respectively.