Lens Antenna Research Articles

Sparse RF Lens Antenna Array Design for AoA Estimation in Wideband Systems: Placement Optimization and Performance Analysis

Sparse RF Lens Antenna Array Design for AoA Estimation in Wideband Systems: Placement Optimization and Performance Analysis

Parameter Sensitivity Analysis of 3D-Printed W-Band Reflective Fresnel Lens Antenna based on Acrylonitrile Butadiene Styrene Plastic

To improve the design of the 3D-printed W-band reflective Fresnel lens antenna based on acrylonitrile butadiene styrene (ABS) plastic, we have examined the parameter sensitivity related to the dielectric material constant. Although we have developed a high-gain millimeter-wave reflective Fresnel lens antenna, the material constant of the ABS filament used in 3D printing needs further investigation to optimize antenna performance. First, a 150-mm-diameter W-band reflector Fresnel antenna is designed and analyzed using finite-difference time-domain (FDTD) analysis. The analyzed and measured maximum antenna gains are 33.3 and 32.4 dBi, respectively. Subsequent sensitivity analysis focused on the impact of the loss tangent, relative dielectric constant, and folding length of the lens, based on both FDTD analysis and measurements.

Electrically tunable virtual image Luneburg lens using graphene.

Virtual image lenses play essential roles in various optical devices and applications, including vision correction, photography, and scientific instruments. Here, we introduce an approach for creating virtual image Luneburg lenses (LL) on graphene. Remarkably, the graphene plasmonic lens (GPL) exhibits electrically tunable virtual focusing capabilities. The design principle of the tunability is based on the nonlinear relationship between surface plasmon polariton (SPP) wave mode index and chemical potential of graphene. By controlling the gate voltage of graphene, we can achieve continuous tuning of virtual focus. A ray-tracing technique is employed to determine the required gate voltages for various virtual focal lengths. The proposed GPL facilitates adjustable virtual focusing, promising advancements in highly adaptive and transformative nanophotonic devices.

Wide-Angle Beam-Switching Antenna with Stable Gain Based on a Virtual Image Lens

Beam-switching antennas based on quasi-optical beamformers can provide cost-effective solutions for high-frequency communication applications. Here, we propose a wide-angle beam-switching planar lens antenna based on the recently presented virtual image lens. The antenna operates from 24 to 28 GHz and produces a beam that can be steered in a 100-degrees range in one plane with less than 2 dB simulated gain variation over the angular range and operational band. The performance of the presented antenna is similar to reported lens antennas with stable gain, but the proposed lens requires a smaller refractive index range to be realized, which alleviates the manufacturing.

Lightweight polypropylene/BaTiO3 composite foams with tunable dielectric constant

Lightweight dielectric foam materials with tunable dielectric constant of 2–1 have broad application prospects in the field of Luneburg lens. Expandable polystyrene (EPS) foam is commonly used for fabricating discrete dielectric layers of Luneburg lens, while its temperature resistance and mechanical properties are poor. EPS foam with dielectric constant of >1.5 is also difficult to prepare because of its low expansion ratio. In this work, choosing polypropylene (PP) with better temperature resistance and mechanical properties as polymer matrix, PP/BaTiO3 composite foams are fabricated by subcritical CO2 batch foaming and steam-chest molding. Through the dual regulation of expansion ratio and mold-opening distance, the dielectric constant of PP/BaTiO3 foams can be tunable from ∼1.19 to ∼1.91, with the density increasing from ∼0.14 to ∼0.59 g/cm3. Compared with EPS foams, PP/BaTiO3 foams have lower density under the similar dielectric constant, indicating the weight reduction of polymer dielectric foam materials by introducing high dielectric fillers.

Design method of a focusing dielectric lens antenna and temperature increment measurement at the focusing spot

In radio wave hyperthermia therapy, array antenna configuration was mainly studied to generate a small spot at the diseased part. Array antennas have the flexibility in controlling radiation performance, such as spot positions, by using their numerous radiating elements. However, the flexibility is achieved at the expense of antenna structure complexity. On the other hand, a lens antenna can concentrate radio waves into a small spot by forming a lens shape. The simplicity of a lens antenna structure lends itself to easy handling in a practical application. Moreover, the frequency independence of the lens antenna allows for a more flexible selection of hyperthermia therapy frequencies. Therefore, the lens antenna is selected as a focusing antenna in this paper. The lens shaping method and the temperature increment measurement are the main contents of this paper. The designed lens has a diameter of 30 cm, a focusing distance of 30 cm, and a working frequency of 2.45 GHz. A thin lens design method is applied to reduce lens weight. Firstly, the focusing ability of the designed lens is ensured by comparing the spot size results of electromagnetic (EM) simulation with its theoretical value. A spot size of 1.77 cm is obtained in both cases. Next, the temperature increment is examined by EM simulations. The temperature at the 2 cm tumor was increased to 41 °C from the human body temperature of 37 °C by an input power of 10 Watts (W). For the temperature increment measurement, a tumor within human body phantom is utilized and the available input power is reduced to 4 W. The tumor temperature increased from 21.5 °C of room temperature to 24.4 °C, which was captured by a thermal imaging camera. As a result, the functionality of the lens antenna for hyperthermia therapy is verified.

Fast Approach for the Simulation of Stratified Spherical Lens Antennas Through Simplified Source Extraction

Fast Approach for the Simulation of Stratified Spherical Lens Antennas Through Simplified Source Extraction

GO Analysis of GRIN Lens Antennas by Combining in a Single ODE, Field and Wavefront-Curvature Transport to the Ray Tracing

GO Analysis of GRIN Lens Antennas by Combining in a Single ODE, Field and Wavefront-Curvature Transport to the Ray Tracing

A 3D printed low‐profile wideband circularly polarised elliptical integrated lens antenna

AbstractThe authors presents a low‐profile wideband circularly polarised (CP) millimetre‐wave (mmWave) elliptical integrated lens antenna (ILA) fabricated by dielectric 3D printing technology. The proposed lens is integrated with a dielectric polariser and an air cavity for phase compensation, which can transfer incident waves from linearly polarised (LP) to planar CP waves over a wide bandwidth. Compared to the classic bifocal ILA, the proposed lens has a low profile. The phase compensation is performed by introducing a specifically shaped air cavity, which greatly reduces the length and weight of the lens. The polariser causes the two electric field components Ex and Ey to degenerate with an orthogonal phase difference, which results in the wideband characteristics of the antenna. The polariser, air cavity and lens can be conveniently and precisely fabricated by low‐cost 3D printing technology. Measurements show that the proposed ILA has a wide axial ratio (AR) bandwidth of 21.9–32.6 GHz, while the gain reaches 22.54 dBic with a 38% size reduction and a 60.7% weight reduction. Benefiting from the low profile, high gain, wide bandwidth and low cost, the proposed ILA has great potential to be the candidate antenna for 5G applications and satellite communications.

Miniaturized Lens Antenna with Enhanced Gain and Dual-Focusing for Millimeter-Wave Radar System.

This paper presents a waveguide Lens antenna at the W-band adopting dual-focusing Lens to improve the performance. The Lens antenna consisted of a waveguide slotted structure and lenses processed using NOA73 meet the demands of miniaturization for current communication systems. The antenna radome fabricated using NOA73 not only protects the antenna structure but also improves the gain of the antenna by about 9.5 dBi via electromagnetic wave dual-focusing. A prototype is fabricated using novel UV-LIGA technology. Measured results are compared with simulated values. Measured results confirmed the fabricated antenna operated in the W-band with a 10 dB fractional bandwidth (FBW) of 6.5% from 97.5 to 104 GHz and a peak gain of 22 dBi at 100 GHz in the direction perpendicular to the plane of the feed waveguide. A good agreement between simulation and measurement is obtained, demonstrating efficient radiations in the operating band.

An improved gain and directivity design of an antipodal Vivaldi antenna for ultra‐wideband detection

AbstractA novel antipodal Vivaldi antenna (AVA) is proposed to achieve improved gain and directivity. To enhance the bandwidth of the antenna, a series of equal‐sized slots are etched onto the patch surface. Additionally, a dielectric lens with a fan‐shaped structure is integrated along the patch openings to boost gain. The length of the lens which will affect the radiation characteristics of the antenna in the end‐fire direction will be discussed. Furthermore, three arrays of directors are added to enhance the directivity. The fabricated antenna is then measured using a vector network analyzer in a microwave chamber to assess its performance. The results indicate that the antenna's minimum operating frequency is reduced by 0.5 GHz after etching the slots. Besides, the average gain is improved by 1 dBi after installing the fan‐shaped expansion structure. By introducing the directors, the sidelobe levels decrease and the 3 dB Half‐Power Beamwidth becomes sharper. Finally, an ultra‐wideband (UWB) detection experiment is designed to analyze the detection capability of the fabricated antennas. The results demonstrate that the antenna is well‐suited for UWB applications.

Wide-angle passive beam steering using 3D modified partial Maxwell fisheye lens

This study presents a broadband, 3D gradient index beam-steering lens, derived from an optimized modification of the partial Maxwell fisheye (PMFE) design, achieving a boresight gain of 23 dBi, -80° to 80° beam steering, and <10 dB gain roll-off. Utilizing fused filament fabrication (FFF) to realize its intricate geometry, the design employs a novel polar space-filling curve (PSFC) to establish a 3D varying, effective permittivity distribution. Rigorous simulations and experimental validation attest to its effectiveness, marking the first 3D implementation of a PMFE-type lens to our knowledge. This research underscores the feasibility and diverse applications of a low-cost, wide-angle passive beam-steering dielectric lens.

Resonant-type Luneburg lens for broadband low-frequency focusing

In this paper, a novel structural Luneburg lens with local resonators is proposed. This lens allows the realization of subwavelength focusing in low-frequency range. The lens is achieved by graded refractive index from the lens's centre to the outer surface. Numerical simulations are conducted to obtain data on wave propagation waveform, maximum displacement amplitude, and full width at half-maximum (FWHM) of the lens's focal region. The results show that a broadband frequency range can be achieved for subwavelength focusing. This provides a straightforward and adaptable method for designing the structural Luneburg lens for numerous applications.

A Lightweight Spherical Generalized Luneburg Lens Antenna With Low Cross-Polarization Over a Wide Range in Azimuth and Elevation

A Lightweight Spherical Generalized Luneburg Lens Antenna With Low Cross-Polarization Over a Wide Range in Azimuth and Elevation

On the Use of an In-Package Dielectric Lens Antenna for Radar-Based Applications

On the Use of an In-Package Dielectric Lens Antenna for Radar-Based Applications

Design of Wideband Flat Artificial Dielectric Lenses at mmWave Frequencies

Design of Wideband Flat Artificial Dielectric Lenses at mmWave Frequencies

A novel mini 0.95MgTiO3-0.05CaTiO3 ceramic Luneburg lens fabricated by vat-photopolymerization 3D printing

With 5G and millimeter-wave technologies evolving rapidly, the high communication frequency leads to high integration and miniaturization of the Luneburg lens (LL). In this paper, a miniaturized K-band flat LL with 0.95MgTiO3–0.05CaTiO3 (95MCT) ceramic was designed and successfully printed by vat-photopolymerization 3D printing. Optimal 3D printing parameters and thermal treatment processes of 95MCT ceramic were investigated. The as-prepared 95MCT ceramic showed excellent properties: a density of 3.40 g/cm3, a high flexural strength of 81.78 MPa, a dielectric constant of 17.7, and a remarkably low dielectric loss value of 4.56 × 10-4. Based on the 95MCT ceramic, a flat LL with a diameter of 40 mm and thickness of 6 mm was printed with sophisticated metastructure. While miniaturization was accomplished with a high degree of dimensional compression, the printed flat LL showed a maximum gain enhancement over 5 dBi. Thus, this study provides a novel viewpoint on the fabrication of microwave dielectric ceramic and miniaturized ceramic radio frequency (RF) devices with complex structures.

3-D printed high-gain elliptic flat Luneburg lens

The antennas on remote sensing satellites play a crucial role in receiving and transmitting wireless signals, affecting data acquisition quality. Among them, Luneburg lens antennas have been successfully applied in satellite tracking due to their high-gain property. However, reducing the flat Luneburg lens(FLL) profile while maintaining performance and addressing manufacturing challenges remains a limitation. This paper first utilizes transformation optics theory to derive the permittivity distribution of the FLL. Moreover, an innovative approach is introduced by multiplying the distribution with a coefficient “g” to achieve the desired lower permittivity required for fabrication. Then, a layered implementation is used to design a circular FLL and improve its performance by compressing its horizontal profile. Therefore, a unique elliptic FLL is proposed by making a trade-off between the gain, beamwidth, and focal length of the lens antenna. The antenna achieves a 22.9 dB maximum gain with beamwidths of 9.5°(E-plane) and 7.4°(H-plane). The elliptic FLL was fabricated using 3D printing technology, and the measured results showed a small deviation from the simulated results within an acceptable range of error. The elliptic FLL possesses design flexibility and holds immense potential in applications such as remote sensing satellite communication.

An E‐band 3D‐printed dielectric lens antenna with flat‐top beam designed by hybrid optimization algorithm

AbstractAn all‐dielectric lens antenna (LA), with flat‐top radiation patterns in both E‐ and H‐planes, is proposed. The antenna covers the 64–70 GHz band. The dielectric LA consists of a source horn (LB‐12‐15‐A with WR12) and a dielectric lens. The lens is composed of multiple layers of dielectric rings with different heights. The structural parameters of the dielectric lens are optimized by a hybrid optimization algorithm (particle swarm optimization [PSO]‐genetic algorithm [GA]) that involves genetic operations of GA and PSO. The hybrid algorithm is beneficial to enhance the optimization efficiency, and an objective function is designed to optimize the beam width, the S11, and the sidelobe level (SLL). Both the simulated and measured results show that the dielectric LA provides good flat‐top radiation patterns within the desired band. Moreover, the dielectric lens is manufactured by three‐dimensional‐printed technology, which allows for low cost, easy manufacturing, and lightweight.

Selection of Parameters of a Multilayer Spherical Luneberg lens in its Implementation by Means of Additive Technologies

The issues of choosing the parameters of a multilayer spherical Luneberg lens (LL) when implementing it using additive technologies are considered. The influence of the electrical dimensions and the method of approximation of the LL on its electrodynamic characteristics is analyzed. The dependences of computational resource costs in the analysis of multilayer spherical structures of this type are given. The parameters of the layers are proposed to ensure the achievement of optimal LL characteristics with a smaller number of splitting of the lens body into layers. The procedure necessary for the implementation of LL by 3D printing is described. The construction of layers of a multilayer lens in the form of a Goldberg polyhedron is proposed. Experimental research data confirmed the results of calculations and modeling.