Lens Antenna Research Articles

Obstacle-tolerant terahertz wireless link using self-healing Bessel beams

Wireless communications using highly directive terahertz (THz) waves exhibit lower immunity to obstructions than microwaves, limiting their applications. This study demonstrates an obstacle-tolerant THz wireless link established by a self-healing Bessel beam at 300 GHz. The Bessel beam is generated by sending a Gaussian beam through a dielectric axicon lens. Furthermore, experiments were conducted to investigate the short-range transmission (98 mm) reception characteristics with and without the dielectric cubic obstacle (7.5 λ in size) and the metallic obstacle (22 λ in length and 8 λ in width) in the Gaussian beam and self-healing Bessel beam cross sections. The maximum attenuation of the received power due to obstruction was 8.8 and 2.2 dB for the Gaussian and Bessel beams, respectively, when the dielectric obstacle is placed in the middle of the transmission path (49 mm from a transmission lens). This study further investigated the bit error rate (BER) characteristics (1 Gbps, on–off keying) with the dielectric obstacle crossing the beam cross section. When the obstacle crosses the Gaussian beam, the BER degrades as the obstacle approaches the optical axis, breaking the wireless link. In contrast, when the obstacle crosses the Bessel beam cross section, the BER is maintained at <3.8 × 10−3 (the forward error correction limit), and the wireless link is maintained. A self-healing beam, such as the Bessel beam, makes the THz wireless link more tolerant than the Gaussian beam to obstacle and expand applications for THz wireless communications.

A compact and fully integrated FMCW radar transceiver combined with a dielectric lens

Abstract Electronic measurement systems in the THz frequency range are often bulky and expensive devices. While some compact single-chip systems operating in the high millimeter-wave frequency range have recently been published, compact measurement systems in the low THz frequency range are still rare. The emergence of new silicon-germanium (SiGe) semiconductor technologies allow the integration of system components, like oscillators, frequency multipliers, frequency dividers, and antennas, operating in the low THz frequency range, into a compact monolithic microwave integrated circuits (MMIC), which contains most components to implement a low-cost and compact frequency-modulated continuous-wave-radar transceiver. This article presents a single transceiver solution containing all necessary components. It introduces a $0.48\,\mathrm{THz}$ radar transceiver MMIC with a tuning range of $43\,\mathrm{GHz}$ and an output power of up to $-9.4\,\mathrm{dBm}$ in the SG13G3 $130\,\mathrm{nm}$ SiGe technology by IHP. The MMIC is complemented by a dielectric lens antenna design consisting of polytetrafluoroethylene, providing up to $39.3\,\mathrm d\mathrm B\mathrm i$ of directivity and half-power beam widths of 0.95∘ in transmit and receive direction. The suppression of clutter from unwanted targets deviating from antenna boresight more than 6∘ is higher than $24.6\,\mathrm d \mathrm B$ in E- and H-Plane.

Design of miniaturized and high gain dielectric lens antenna

AbstractA miniaturized and high‐gain dielectric lens antenna is presented and demonstrated. The dielectric lens antenna is mainly composed of a spherical dielectric lens, a pedestal, and a radiating element. The spherical dielectric lens is made of a special material called cross‐linked styrene co‐polymer showing an ultra‐low dielectric loss and a stable permittivity. The pedestal is made by the 3D printing technique and used for supporting the dielectric lens. The radiating element is embedded in the bottom of the pedestal, a proper spacing between the dielectric lens and the radiating element is maintained. The proposed dielectric lens antenna shows impedance bandwidth ranging from 24.4 to 25.8 GHz and an excellent directional radiation characteristic is obtained.

Design, Simulation, and Construction of a SWB Antenna Using a Metasurface Luneburg LENS

Design, Simulation, and Construction of a SWB Antenna Using a Metasurface Luneburg LENS

1-to-N terahertz integrated switches enabling multi-beam antennas

Implementing terahertz circuits and system designs relies on integrating reconfigurable devices such as switches, to fulfill a critical role in controlling and manipulating the flow of terahertz signals on the chip. Although there have been several demonstrations of on–off switching in the terahertz range, there have been no demonstrations of 1-to-N switching, to our knowledge. This pronounced lack of dynamically reconfigurable routing has severely limited the achievable complexity of terahertz systems. To address this, we propose 1-to-N switches made of cascaded disk resonators integrated into a substrateless silicon waveguide platform. A single switch can be controlled via photoexcitation using a low-power 658-nm laser focused onto the disk resonator, turning off the resonance and inhibiting coupling into a crossing port. The measurement results demonstrate that the proposed switch has low insertion loss, which can be attributed to the inherently low dissipation of the platform. The proposed on–off switch achieves a maximum insertion loss of 1.2 dB, and the maximum extinction ratio of the switch is 16.1 dB with 1.5 GHz of bandwidth. Furthermore, a 1-to-3 switch is monolithically integrated together with a Luneburg lens in order to project each of its output ports to a different far-field direction and, thereby, translate the switching operation into a form of reconfigurable beam control for future applications.

Electromagnetic near-field focusing based on metasurfaces

Near-field electromagnetic focusing has become a hot research topic due to its high application value in wireless transmission, wireless sensing, biomedicine, and radio frequency identification. In this paper, anisotropic metasurfaces have been proposed to manipulate the phase of the electromagnetic (EM) wave for obtaining EM near-field focusing. Under orthogonal linearly polarized incidence, dual focus functions can be realized independently for polarization multiplexing on the metasurfaces. Meanwhile, Single focus and multi focus with different energy distributions and focal position is obtained by the proposed metasurfaces. By using the Vivaldi antenna as the feed source positioning at the focal of the metasurfaces, a lens antenna with high gain is obtained with circularly polarized far-field mode and broadband characteristics. Due to the unique advantages of metasurfaces in modulating the phase distribution of EM waves, the proposed method may pave a new way for EM focusing application.

23.1-Gb/s 135-GHz Wireless Transmission Over 4.6-Km and Effect of Rain Attenuation

In this article, we have experimentally demonstrated a fiber-wireless-integration <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$D$</tex-math> </inline-formula> -band (110–170 GHz) transmission system. To extend the wireless transmission distance while maintaining the wireless bit rate as high as possible, we designed high-gain lens horn antenna modules consisting of a pair of dielectric plano-convex lenses and horn antennas for long-haul wireless links. In addition, we employ the Volterra nonlinear equalization (VNE) algorithm based on the multiple-input–multiple-output (MIMO) structure to precisely compensate for the in-phase/quadrature (I/Q) imbalance and nonlinear impairment of quadrature amplitude modulation (QAM) signals mainly caused by photoelectric (O-E) conversion and electric-photo (E-O) conversion. Meanwhile, one of the methods adopted in our experiment to decrease the influence of nonlinearity on high-order QAM signals is coupling the high-order modulation format with the probabilistic shaping (PS) technology. As a result of outdoor field experimental verification, the demonstration at 135 GHz carrier with a net rate of 23.1 Gb/s over 10 km optic-fiber and 4.6 km wireless transmission distance has been successfully carried out. It is, as we know, the first time that a record-breaking product of net bit rate and wireless transmission distance, i.e., 23.1 Gb/s <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> 4.6 km <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$=$</tex-math> </inline-formula> 106.3 Gb/s <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot$</tex-math> </inline-formula> km, has been accomplished based on a fiber-wireless-integration system. Also, for the first time, we have measured the effect of rain attenuation for the 135 GHz millimeter-wave (mm-wave) wireless link and established more accurate rainfall models for the Shanghai region of China by comparing them with multiple rainfall models. This work can be used as a complement to the International Telecommunication Union-Radiocommunication sector (ITU-R) recommendations.

Truncated 2-D Gutman Lens Antenna With Planar Feeding Surface for Stable Wide-Angle Beam Scanning in Millimeter-Waveband

Truncated 2-D Gutman Lens Antenna With Planar Feeding Surface for Stable Wide-Angle Beam Scanning in Millimeter-Waveband

Dual-Polarized Antenna Feed Matrix Design for Multibeam Lens Antenna

Dual-Polarized Antenna Feed Matrix Design for Multibeam Lens Antenna

High-solid-content paste for stereolithography self-supporting printing of Luneburg lenses with a high degree of geometric-design freedom

Luneburg lenses prepared by alumina stereolithography, have the advantages of low dielectric loss, corrosion resistance, and flexible structure. However, the supporting structure limits the degree of geometric design freedom. This paper analyzes the effects of modifiers and dispersants on paste properties from the molecular structure, which is different from the traditional process that doesn’t analyze the influence of similar mechanisms and binding site competition while ignoring the correlation. Based on the dispersant’s better flexibility bringing more obvious change in viscosity, we first determine the amount of dispersant and then adapt the amount of modifier to obtain self-supporting pastes of 82 wt % and 24.9 Pa.swithout gradation. The gain and beam deflection angle of Luneburg lenses with high geometric complexity and working bandwidth of 38° formed by stereolithography self-supporting process is matched to the simulation results without manufacturing defects, which provides a theoretical basis for more flexible design and manufacture of Luneburg lenses.

An All‐Silicon Metalens Integrated with a Mid‐Wave Infrared Black Phosphorus Photodiode

AbstractBlack phosphorus (BP) is a promising material for mid‐wave infrared (MWIR) photodetection because of its direct tunable bandgap and compatibility with a wide range of substrates, particularly silicon. However, optical signal collection in BP devices can be limited by its absorber thickness or active area. Dielectric metasurface lenses, which can be directly integrated into a device's substrate, are a scalable approach to increase the signal collected by BP photodetectors. This work presents the design, fabrication, and characterization of an all‐silicon metasurface lens for focusing MWIR light through its substrate. Then, a BP‐MoS2 heterojunction photodetector is integrated with the metalens, and MWIR photodetection increases at room temperature. These results demonstrate that integrated metasurface lenses are an excellent approach for boosting the performance of MWIR BP photodetectors.

Differential beamforming using Rotman lens for wireless sensor networks

In this article, an optimal beamforming technique using a low cost intelligent Rotman lens antenna is proposed. The proposed technique enjoys full diversity with high coding gain, has a very low encoding and decoding complexity, and does not require channel knowledge at any transmitting or receiving antenna. From our simulation results, the proposed technique outperforms the best known non-coherent multi-antenna techniques. Furthermore, we prove that the BER expressions obtained from the theoretical analysis enjoy full diversity gain and match our conducted simulations.

E-band backhaul antenna for fine beam alignment

Abstract An E-band Cassegrain switched beam high-gain antenna concept for 5G backhauling systems is proposed in this article. The antenna requirements target the compensation of small misalignments (within ±1 degrees in both azimuth and elevation planes) in E-band backhauling links due to adverse weather conditions or thermal deformations. The intended antenna is able to realize beam-switching operations by using a feed-array architecture based on a 7 × 7 array of cavity-backed magnetoelectric (ME) dipoles, where every element is capable of providing a steering of ±0.33 degrees in both the elevation and the azimuth planes. The ME dipole illuminators combined with a Cassegrain reflector provide a gain of 52 dBi within the whole scanning range. Besides, they can be easily integrable with the front-end modules, thus being an easily implementable and low-cost alternative to other more complex solutions based on horns or lens antennas.

Experimental realization of an ultra-thin and continuous scanning metasurface mimicking a Luneburg lens

Luneburg lens is traditionally a spherical dielectric with centro-symmetric and graded refractive index, which has been widely applied in civilian and military fields due to its outstanding abilities of focusing or collimating electromagnetic waves. However, the existing designs of Luneburg lens generally suffer from the disadvantages of bulkiness, complex fabrication process, and limited scanning angles, etc. Herein, a planar metasurface that could mimic the planar Luneburg lens is designed by utilizing the addition theorem. It has been experimentally verified that the Luneburg-like lens has large and continuous scanning angles from −52° to 52° at a frequency of 10 GHz if an excitation antenna is moved along a straight line. Besides, the total thickness of the proposed lens is only 3 mm and it has the advantages of low cost, ease of fabrication, as well as being isolated from the feeder. As a result, the proposed Luneburg-like lens has great potential values of being flexibly applied in numerous fields.

Beam-steering of dielectric flat lens nanoantenna with elliptical patch based on antenna displacement for optical wireless applications

In this paper, the switched-beam nanoantenna (NA) concept is introduced with a theoretical design of an inhomogeneous dielectric flat lens modelled with different materials to steer and enhance the radiation in a particular direction based on shifting the illuminator element. Firstly, the design of hybrid plasmonic NA is introduced and analyzed considering different silicon patch shapes such as rectangular, circular, hexagonal, and elliptical shapes. The elliptical patch NA achieves a gain of up to 10.7 dBi and a return loss of − 14.41 dB. Then the design of a gradient-index dielectric flat lens with the NA is introduced to improve the antenna performance by increasing the directivity and consequently decreasing the beam-width. Furthermore, the beam-steering capabilities by displacement of the NA according to different feeding points along the X and Y-direction. By using the gradient-index dielectric flat lens, the gain is increased to 18.4 dBi with an improvement in the return loss reach to − 19.15 dB compared with traditional NA. In addition, the beam-steering capabilities were achieved with a range ± 60° × ± 55° with acceptable average antenna gain, side-lobe levels, and half power beam-width of 16.5 dBi, − 12.3 dB and 13.6° respectively.

Subwavelength pulse focusing and perfect absorption in the Maxwell fish-eye

Maxwell's fish-eye is a paradigm for an absolute optical instrument with a refractive index deduced from the stereographic projection of a sphere on a plane. We investigate experimentally the dynamics of flexural waves in a thin plate with a thickness varying according to the Maxwell fish-eye index profile and a clamped boundary. We demonstrate subwavelength focusing and temporal pulse compression at the image point. This is achieved by introducing a sink emitting a cancelling signal optimally shaped using a time-reversal procedure. Perfect absorption and outward going wave cancellation at the focus point are demonstrated. The time evolution of the kinetic energy stored inside the cavity reveals that the sink absorbs energy out of the plate ten times faster than the natural decay rate.

3D-Printed Dielectric Rods for Radar Range Enhancement

A design strategy to alter the radiation characteristics of modular radar printed circuit boards without the need for expensive retooling and remanufacturing is presented in this paper. To this end, a compact radar module including microstrip array antennas integrated with a dielectric rod lens is considered for a demonstration of an X-band radar antenna gain improvement leading to radar detection range enhancement. Using travelling wave theory, the proposed lens is designed to target the excitation of HE11 mode to achieve gain improvement without disturbing reflection coefficients. Using a low-cost rapid-manufacturing 3D-printing technology, two pairs of the 3D-printed dielectric rods integrated with a dielectric housing are designed and fabricated uniformly for a commercially available off-the-shelf radar module. The radar integration with the dielectric rod lens leads to a low-cost and easy-to-fabricate long-range radar system. Compared with the radar without the rods, the design system achieved a measured 6.6 dB gain improvement of the transmitter and receiver antennas which causes doubling the detection range for both elevation and azimuth directions at 10.525 GHz.

Intelligent Simulation Technology Based on RCS Imaging

The target simulation of airplanes is an important research topic. It is particularly important to find the right balance between high performance and low cost. In order to balance the contradictions between realistic target simulations and controllable costs, the scientific formulation of the performance parameters of target simulation is the key to achieving high performance. This paper proposes an intelligent simulation technology based on RCS imaging simulation through the combination of 60° variation corner reflector and a Luneberg lens reflector. It is designed to simulate several important RCS characteristics of the aircraft. At the same time, the different RCS images are automatically shifted to the corresponding gear position to achieve the purpose of simulation, and the price is low and the performance is good. It can be used for the training of radar target searching.

Electrically tunable graphene plasmonic lens: from Maxwell Fisheye Lens to Luneburg Lens

A graphene plasmonic lens with an electrically tunable focal length is proposed and numerically investigated. The design philosophy of the proposed tunable lens is based on the nonlinear relationship of surface plasmon polariton (SPP) wave index with respect to chemical potential of graphene. By controlling the gate voltage of graphene, the proposed lens can be continuously tuned from a Maxwell Fisheye lens to a Luneburg lens. A ray-tracing method is employed to find out the corresponding gate voltages for various focal lengths. Full-wave EM simulations using COMSOL show that excellent focusing performances can be achieved. This work offers a new way in exploiting active transformational plasmonic elements in the mid-infrared region.

Thermally driven hybrid metastructure for multi-functional surface acoustic wave engineering

Acoustic wave engineering through solid mediums are essential for improving or optimizing the performances of various platforms, such as biomedical and industrial applications. Metamaterials or metasurfaces have been recently developed to artificially manipulate the wave propagation passing through mediums. However, they only conduct one fixed function passively, determined by the structure design for the particular wavelength, and their fabrication involves high-cost and complex procedures. Here, we report a thermally driven hybrid metastructure (HMS) for actively controlling surface acoustic waves. The HMS is designed as the layered structure of a thermoresponsive polymer (TP), thermal metamaterials (TMs) and an intermediate layer (IL) made of silica aerogel. For providing multi-functions, TPs conduct the considerable elastic modulus changes and corresponding wave manipulation at a certain glass transition temperature while TMs enable the programmed heating configuration, and the IL mitigates thermal and acoustic wave interference. By introducing the IL, the entire energy of the propagating wave is captured at the interface and interference between the wave and thermal energy is prevented, which directly reflects the temperature control through the TMs into the TP heating configuration. Versatile functions of programmable wave engineering including omnidirectional wave focusing-collimation through modified Luneberg lenses, dual-functioning focusing-bifurcation, and double refraction through 3-phase wave steering are demonstrated using the proposed HMS implemented by the temperature gradient design of TMs. This work will inspire tunable and scalable platforms for active controls of wave propagation enabled by thermal energy as a driving force.