Jie Wu

This letter introduces a compact electronically tunable antenna capable of reconfiguring its polarization and beam direction. The designed antenna consists, from top to bottom, of a Circular Reconfigurable Metallic Wire (CRMW) layer, a parasitic patch layer, and a driven antenna multilayer board. By programming the FPGA to control the PIN diodes on the CRMW, the length distribution of the metallic segments can be changed, enabling beam reconfiguration. Additionally, the PIN diodes on the DC feeding network (DFN) allow for rapid switching among six polarization states. The effective overlapping operating frequency range for all beam states is 3.5 to 3.8 GHz. The radiation beam varies in two dimensions: with an azimuth range from 0 to 360° and an elevation range from -30° to +30°. The experimental results show excellent agreement with simulations for 18 different beam states. Furthermore, the antenna achieves an average peak gain of 7.1 dBi, with a total efficiency exceeding 55.9% across all reconfigurable states. The antenna has potential applications in multifunctional integrated systems for drone communications and anti-jamming systems.

This letter reports a wide band linearly polarized(LP) and orbital angular momentum (OAM) mode reconfigurable magneto-electric (ME) dipole antenna array. A switchable microstrip balanced feed structure (MBFS), which can provide a stable phase difference of 180-degree in the whole operating frequency band, is employed in the design of ME dipole element. By using two orthogonal MBFS, two high-isolation LP modes with switchable 180-degree phase shifting characteristics can be generated, enabling the reconstruction of LP modes through polarization synthesis. By manipulating the states of the reconfigurable feed network and the four ME dipole elements, the polarization can be altered among two orthogonal LP states and the OAM mode can be reconfigured between l=-1,0,and+1.The measurement results indicate that the proposed ME dipole array exhibits good reflection coefficient in the frequency range of 3.0-4.0 GHz (|S11| < -10 dB) and demonstrates excellent reconstruction capability in both polarization and OAM modes.

This article presents a novel continuous meta-grating array (MGA) for the generation of ultra-wideband, near-perfect orbital angular momentum (OAM) beams with extremely high mode purity. First, a novel dielectric-doping strategy is proposed to overcome the inherent narrowband characteristics of conventional grating atoms, resulting in an ultra-wideband dielectric-doping meta-grating atom (DDGA). By establishing an equivalent circuit model (ECM), the operational mechanism is analyzed. The design method is provided to establish clear DDGA design guidelines to follow. Simulation and ECM calculations reveal that within the 9.06–19.88 GHz (74.7%), the circularly co-polarized reflection coefficient and polarization conversion ratio exceed 99.7% and 98.7%, respectively. Subsequently, a space-variant sub wavelength MGA is generated using grating functions. The continuous grating array ensures the continuity of the reflected field, thereby avoiding beam distortions and low mode purity that may result from potential mutual coupling and diffraction effects caused by discontinuities in traditional metasurfaces. In the 9.0–21.0 GHz (80.0%), the MGA is capable of generating near-perfect vortex beams, ranging from low-orders to high-orders, with extremely high purity and very low mode crosstalk. In addition, it demonstrates frequency-aperture size insensitivity and dual-wideband properties, facilitating miniaturization and size customization while delivering high-performance OAM in the high-frequency 37–50 GHz. Finally, experimental validation confirms the effectiveness.

This paper presents a novel continuous dielectric meta-grating array (DMGA) for generating wideband, high-performance transmission orbital angular momentum (OAM) vortex beams with high mode purity. A broadband meta-grating unit (MGU) was designed and modeled theoretically, including a detailed analysis of its design process. Simulations and theoretical calculations show that, in the 26-39 GHz (40%), the unit achieves a 180° transmission phase and a transmission coefficient over 0.9. The array patterning was determined using a grating function. The DMGA is composed of continuously spatially varying grating strips, effectively preventing issues caused by array discontinuity such as inter-atom coupling and discontinuous step phase changes, which could lead to vortex beam distortion and low purity. Simulations show that the DMGA generates broadband, high-performance vortex beams with high mode purity for mode orders l = 2, 3, 4, 5, 6, 7, 8, 9, and 10, exhibiting advantages in generating high-quality, high-order OAM beams. Additionally, it exhibits frequency-aperture size insensitivity, enabling miniaturization and customization of aperture sizes. Finally, the measurement confirms the effectiveness.

The performance of holographic multiple-input multiple-output (MIMO) communications, employing two-dimensional (2-D) planar antenna arrays, is typically compromised by finite degrees-of-freedom (DOF) stemming from limited array size. The DOF constraint becomes significant when the element spacing approaches approximately half a wavelength, thereby restricting the overall performance of MIMO systems. To break this inherent limitation, we propose a novel three-dimensional (3-D) antenna array that strategically explores the untapped vertical dimension. We investigate the performance of MIMO systems utilizing 3-D arrays across different multi-path scenarios, encompassing Rayleigh channels with varying angular spreads and the 3rd generation partnership project (3GPP) channels. We subsequently showcase the advantages of these 3-D arrays over their 2-D counterparts with the same aperture sizes. As a proof of concept, a practical dipole-based 3-D array, facilitated by an electromagnetic band-gap (EBG) reflecting surface, is conceived, constructed, and evaluated. The experimental results align closely with full-wave simulations, and channel simulations substantiate that the DOF and capacity constraints of traditional holographic MIMO systems can be surpassed by adopting such a 3-D array configuration.

A circularly polarized (CP) reconfigurable and linear polarized (LP) orbital angular momentum (OAM) mode multiplexing concentric uniform circular array (CUCA) is presented. The designed antenna array consists of two parts: an inner UCA composed of four LP antenna elements and an external UCA composed of eight sequentially rotated CP reconfigurable elements. The inner UCA and outer UCA are capable of generating multiplexed OAM beams at 3.28 GHz with l = +1 and mode l = ±2, respectively. To assess the performance of these vortex beams, a purity analysis of the multiplexed OAM modes was conducted. When all elements are fed with the same amplitude signal, the mode purity of the inner UCA at l = +1 with LP is 27.6%. As for the external UCA, at l = +2 with right-hand CP (RHCP), the mode purity in the electric field Ex- component is 32.5%, and in the Ey- component, it is 47.5%. Furthermore, l = -2 with left-hand CP (LHCP) has similar results. The obtained results are consistent, validating the potential application of the proposed modal multiplexing method in future communication.

A microstrip dual-split-ring antenna array for fifth-generation (5G) millimeter-wave dual-band applications is presented in this letter. The microstrip dual-split-ring structure is adopted to generate two resonance points operating at 28/38 GHz dual band, respectively. To improve the radiation characteristics at 38 GHz band, two branches are added to the middle of microstrip dual-split-ring structure. Finally, the proposed 1 × 4 microstrip dual-split-ring antenna array can achieve impedance bandwidths of 12.5% (26–29.5 GHz) and 5.3% (36.7–38.7 GHz), and peak gains of 12.7 and 14.9 dBi at 28/38 GHz dual band, respectively. The proposed antenna array with one signal chain has these advantages of simple structure, wider dual-band impedance and gain bandwidths, higher gain and lower sidelobe level. Therefore, the design scheme will be suitable for the 5G millimeter-wave dual-band applications.

In this article, a low-profile compact array antenna using polarization-agile and frequency-tailored capabilities with digital-controllable radiation beams is presented. The antenna element consists of a square patch loaded by four capacitors and four switchable feeding ports which are controlled by a field-programmable gate array (FPGA). The frequency of the resulting structure can be altered from 1.35 to 2.19 GHz based on a compact size by choosing different capacitance values from 0.31 to 3.14 pF. By designing the coding patterns of the digital radiating elements, various radiation beams with three different linear polarization (+45°-LP, −45°-LP, and V-LP) can be achieved and arbitrarily controlled based on one antenna aperture. The simulation and experimental results demonstrate an acceptable agreement, which proves the polarization-agile and beam-controllable characteristic of the designed array antennas at three different frequency bands corresponding to 0.3, 1.0, and 3.0 pF. The multifaceted reconfiguration capability enables it to meet the needs of signal quality stability in many future communication systems.

A low-profile wideband circularly polarized (CP) millimeter-wave (mm-Wave) L-shaped dipole antenna with hexagonal parasitic patches is presented in this letter. Two types of hexagonal parasitic patches are placed round the rotationally symmetrical L-shaped dipole to enhance the impedance and axial ratio (AR) bandwidth. Based on this antenna element, a substrate integrated waveguide-fed 2 × 2 subarray with sequential rotate feeding technique is designed to further improve AR bandwidth. Finally, a 4 × 4 CP array is designed to further enhance the gain. The measurement shows the proposed array can achieve the impedance bandwidth of 27.7%, the AR bandwidth of 28.5%, and the peak gain of 17.85 dBic while maintaining a lower profile. Therefore, the design scheme will be suitable for 5G mm-Wave communications and satellite communication systems.

In this letter, a 2x2 wideband bidirectional dual circularly polarized (CP) orbital angular momentum (OAM) antenna array at millimeter-wave frequency is presented, which can be used to generate dual-mode simultaneously by the sequential rotation feeding (SRF) method. The proposed antenna array is composed of four bidirectional radiating dual-CP elements that rotate 90 degrees sequentially to each other in the clockwise direction. The antenna element structure consists of two metasurface patch layers which are loaded on the bidirectional cavity-back slot antenna based on substrate integrated waveguide (SIW) technology. Results indicate that the left-hand circular polarization (LHCP) with a mode lOAM = -1 in +z direction and right-hand circular polarization (RHCP) with a mode lOAM = +1 in z direction, over a wide impedance (S11 10 dB) and 3-dB axial ratio (AR) relative bandwidth of 32.3% from 26 to 36 GHz. An acceptable agreement has been achieved with the comparison between the measurement and simulation results. The proposed antenna provides a method of generating multi-mode OAM beams for wideband millimeter-wave wireless communication applications.