Beam-steering Antenna Research Articles

Nonuniform Amplitude Transmitarray for Multibeam Including Near-Field Focusing

This article presents a nonuniform amplitude transmitarray for a multibeam that includes near-field focusing, based on a frequency selective surface (FSS). Each cell on the FSS is fed by a slot array and its feeding magnitude is adjusted by the slot position. The phase sets required for near-field focusing and far-field steering are controlled by the cell size of the FSS located above each slot. To confirm the performances of the antenna, a multibeam antenna for beam focusing and steering is designed. The required phase and amplitude of each cell are simply calculated and optimized by the principle of superposition. Finally, a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$6 \times 4$ </tex-math></inline-formula> array prototype antenna operating at 5.8 GHz is realized, and its characteristics are measured. The antenna can simultaneously focus on a near-field spot and radiate in the desired far-field direction. The measured and simulated results are found to be in good agreement.

High Aperture Efficiency Arced Conformal Array With Phasor Beam Steering Antenna

A phasor beam steering stacked patch antenna with abilities of both the amplitude and phase pattern reconfigurations is proposed and used for improving the aperture efficiency of arced conformal array. The phasor beam steering antenna is composed of two parasitic patches on the top integrated with four PIN diodes and a driven patch on the lower layer. By switching the bias states of the PIN diodes, the induced complex current of the top patch is alterable and the phasor beam steering can be delivered. Thus, in the conformal array design, the phase compensation can be realized by the phase pattern reconfiguration of the phasor beam steering antenna instead of the conventionally used phase delay lines. Meanwhile, the amplitude pattern reconfiguration of the phasor beam steering antenna can also be used for enhancing the contribution of side elements to the gain of axial beam. A four-element arced conformal array with the phasor beam steering antenna is designed and measured for verification. Both the simulated and measured results indicate that the realized gain of the proposed conformal array is 12.0 dBi, and the corresponding aperture efficiencies are improved up to 51.48%, which is better than the results of the arced conformal array with the phase compensation network.

State-of-the-Art Passive Beam-Steering Antenna Technologies: Challenges and Capabilities

State-of-the-Art Passive Beam-Steering Antenna Technologies: Challenges and Capabilities

3D Printed Directive Beam-Steering Antenna Based on Gradient Index Flat Lens With an Integrated Polarizer for Dual Circular Polarization at W-Band

In this communication, the design of a circularly polarized (CP) perforated gradient index (GRIN) flat lens antenna with directive beam-steering properties is presented for millimeter-wave applications at W-band (75–95 GHz). The dielectric lens, fed by an open-ended square waveguide (SWG) located in the lens focal plane, enhances the radiation in a particular direction, generating a high-directivity beam with planar wavefront. The integration of a dielectric polarizer with the lens allows the conversion from a linearly polarized (LP) incident wave to a CP-emitted wave over the whole bandwidth. Horizontally and vertically polarized waves, achieved by the excitation of the fundamental SWG TE01 and TE10 modes are transformed into left-hand CP and right-hand CP waves, respectively. A ±30° scan range in both azimuth and elevation planes is demonstrated for the whole frequency range, attained by displacing the feed along the focal plane of the lens. Lens and polarizer are manufactured as a single piece by stereolithography (SLA) 3-D printing technology with Form 3 Formlabs 3-D-printer. Measured results show maximum measured directivity values that range from 23.5 to 23.8 dB, a remarkable circular polarization purity as a wide axial ratio bandwidth of 20.58% (< 3 dB), from 77.5 to 95 GHz, is achieved for the principal beam steers and an aperture efficiency for broadside beam direction between 90.32% and 57.34% in the frequency band of interest.

2-Dimensional (2D) Beam Steering-Antenna Using Active PRS for 5G Applications.

This paper presents a compact coaxial-fed square microstrip patch antenna integrated with a beam-steering Partially Reflective Surface (PRS). The proposed design has a two-dimensional (2-D) Fabry-Perot Cavity (FPC) antenna acting as a radiator and the PRS as a beam-steering superstrate operating at 5.5 GHz. The PRS consists of 6 × 6 reconfigurable unit cells etched on Rogers 5880 with a thickness of 1.57 mm. By controlling the switching of PIN diodes in different sections of PRS, beam steering can be achieved up to ±47° in the azimuth plane with a gain of 9.1 dB and 10.2 dB and ± 15° steering in an elevation plane with a measured gain of 9.3 dB and 8.9 dB, respectively. The antenna prototype is 2.56 λ × 2.56 λ at 5.5 GHz, and the measured gain values are around 10 dBi for all the states. The beam is able to radiate at boresight or tilted to 42° in two azimuthal directions and 45° in elevation direction by adjusting the PIN diodes ON/OFF states. The 10 dB impedance bandwidth of 5.4-5.52 GHz is achieved.

Millimeter-Wave Beam Steerable Slot Array Antenna Using an Inter-Digitated Capacitor Based Corrugated SIW

A new class of electronically beam-steerable corrugated substrate integrated waveguide (CSIW) slot array antenna operating at 26–29 GHz has been developed. The conventional via-based walls of substrate integrated waveguides (SIWs) or stub-based walls of CSIWs have been replaced with an interdigitated capacitor (IDC) structure to enable reconfigurability. This novel IDC-CSIW is shown to have a lower transmission loss compared with conventional CSIWs in the literature. A new mathematical method has been described to calculate the cutoff frequency of IDC-CSIWs. The surface of the IDC-CSIW is then loaded with longitudinal slots, building a leaky-wave architecture. Radiation from individual slots is controlled by shorting the IDC at specific points using p-i-n diodes. The antenna is fed at either end using a single-pole–double-throw (SPDT) switch to achieve a 2-D reconfigurable beam. A compact switched array of two IDC-CSIWs is demonstrated to produce a continuous full sector coverage of 120° in the azimuth plane and ±15° in the elevation plane, providing a 2-D beam steer with a stable gain of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 13.5$ </tex-math></inline-formula> dBi and an efficiency greater than 80%.

Design technique to mitigate unwanted coupling in densely packed radiating elements of an antenna array for electronic devices and wireless communication systems operating in the millimeter-wave band

A feasibility study of an innovative design is presented of a metamaterial inspired antenna array for millimeter-wave band applications where non-mechanical beam-steering is required such as in 5G and 6G communications, automotive and radar systems. In communication systems beam-steering antennas can significantly improve signal-to-noise ratio, spatial directivity, and the efficiency of data transmission. However, in tightly packed arrays the effects of mutual coupling between the radiating elements can severely limit the array’s performance. The proposed antenna array consists of a 3 × 3 matrix of patch radiators that are tightly packed and interconnected to each other. Rows of radiators are demarcated by a horizontal microstrip transmission-line whose ends are short-circuited to the ground-plane. This technique reduces unwanted surface waves that contribute to undesired coupling. Embedded in the square patch radiators is a rhombus shaped slot that increases the effective aperture of the antenna with no impact on the antenna’s size. As the antenna is excited via a single feedline the edge-to-edge spacing between the radiators and the interconnected feedlines are made such that there is phase coherency at the radiating elements. Measured results show that the effectiveness of the proposed array in simultaneously improving its impedance bandwidth and radiation characteristics. The measured peak gain and radiation efficiency are 13.6 dBi and 89.54 %, respectively.

Guest Editorial Disruptive Beam-Steering Antenna Technologies for Emerging and Future Satellite Services

The papers in this special section focus on the state-of-the-art of applied and analytical research, including the latest technological advancements and the use of innovative materials and methods to disrupt the way beam-steering antennas are designed and to reveal novel approaches for the design and analysis of antennas for the next generation of satellite communication systems.

Mechanical Beam Steering Array Antenna With Tunable Height

This letter presents a mechanical beam steering array antenna (MBSA) with tunable height elements. Each antenna element is composed of a U-slot radiation patch and a stepper motor supported by the three-dimensional-printed structure. By controlling the height of each antenna element using a stepper motor, an arbitrary phase shift value in the range of 0°∼360° can be achieved. In addition, steering high-gain beams can be generated by flexibly adjusting the height of each antenna element. A prototype of 8 × 8 MBSA was designed and fabricated to realize beam scanning in the pitch angle range from −40° to 40° in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">xoz-</i> plane and near-field focusing. The measured gain of MBSA is 23.3 dBi with an aperture efficiency of 85.7% at 10 GHz. The proposed MBSA has the advantages of simple structure, low cost and high stability, which can be applied in satellite communication systems.

Reconfigurable Half-Mode SIW Antenna Using Uniaxial Field Programmable Microwave Substrate Structure

This communication presents the design and implementation of a beam steerable leaky wave antenna (LWA) based on integrated electronic devices (varactor diodes). The design uses a half-mode substrate-integrated waveguide (HMSIW) where the short-circuited wall or PEC boundary is realized with field programmable microwave substrate (FPMS)-based unit cells. By virtue of placing integrated varactor diodes in these unit cells, the wavenumber and the phase shift of the propagating signal can be controlled. This allows a beam steering of 25° for a fixed center frequency. Furthermore, control of the varactor bias voltages allows a fixed beam direction over a wide frequency bandwidth. An excellent agreement can be observed between the simulated and measured results, validating the first ever FPMS-based reconfigurable antenna design.

Characteristic Modes-Inspired Polarization Twisting Metasurface Element for 1-bit Folded Reflectarray

A 1-bit folded reflectarray (FRA) based on characteristic modes-inspired polarization twisting metasurface element is proposed. The element is inspired by a 2×2 patch-based metasurface where a corner patch is removed and a pair of the patch is connected to break the symmetry for polarization twist and reduce the number of switches with the assistance of the characteristic mode analysis. On this basis, only two switches are required in each element for 1-bit phase encoding. To verify the proposed metasurface element, two 1-bit FRA in the Ka-band with beam directions of 0° and 60° are designed and fabricated where the metal stubs/open circuits are employed instead of real switches. The measured peak gains reach 27.4 dBi at 30 GHz with an aperture efficiency of 21.2% and a 3 dB bandwidth of 16.2%. This FRA exhibits good beam scanning characteristics with high gain and wide fractional bandwidth, which shows great potential in the application of low-cost electronically beam-steerable antennas.

ARIEL: Passive Beam-Scanning Antenna teRminal for Iridescent and Efficient LEO Satellite Connectivity

A novel low-cost high-gain beam-steering antenna terminal topology for global data connectivity with low-earth-orbit satellite constellations in the UHF 900 MHz ISM band is reported. It is shown how a simple printed-circuit-board half-width microstrip leaky-wave antenna (LWA) with passive frequency-beam scanning capacity provides an energy-efficient scanning method avoiding more power-demanding and expensive beam-steering techniques (such as electronic scanning, mechanical rotation, or beam switching). For that, iridescent channel-agile operation and cross-layer optimization are needed. As an example, two single-element LWAs and an LWA array are designed to scan the celestial vault with an angular elevation scanning range of 130° and using the available LoRaWAN protocol channels from 902 to 928 MHz. It is reported a scanned-beam peak gain above 9 dBi for the compact printed-circuit LWA array design with 55 cm × 27 cm aperture dimensions.

Tunable Multibeam Holographic Metasurface Antenna

A metasurface beam-steering antenna at microwaves is proposed in this letter, which is designed according to holographic theory and has the ability to create multibeam radiation patterns with independent control of the individual beam direction. The holographic design approach of the modulated impedance surface follows the methodology of linear superposition of individual field patterns for each beam. The unit cell of the proposed antenna is tuned with a low-loss varactor diode, and its dispersion diagram is obtained with a transverse resonance technique. A novel multibeam antenna fed by a single source is designed with independent beam steering of each beam at around 7.2 GHz. The dual-beam antenna exhibits an average of 11.6 dBi of realized gain for each independent beam.

A Direct Antenna Modulator With Beam Steering Capability Based on Space-Time-Coding Arrays

We propose an RF front-end architecture with simultaneous direct antenna modulation and beam steering capability based on space-time-coding (STC) arrays. In an STC array, digital codes control the state of each array element. The element state determines the amplitude and phase of the radiated wave, and in a time scale over which the state of the elements is changed by a few successive codes, the frequency harmonics are generated. We first introduce a vector representation of bits in a code and their effects on the resultant harmonic wavefront. We show that by choosing proper codes with a minimum of two repetitions, one can modulate data on the phase and amplitude of a desired far-field harmonic where proof-of-concept simulations are given for a 16-APSK digital modulation scheme. We investigate the data rate, spectral efficiency, and the limitation of switching speed in our proposed scheme. Moreover, it is shown that the harmonic beam patterns of an STC array can be easily steered by a consecutive shifting of bits in the code without affecting the transmitted data symbols. Through cosimulation of digital design and coded antenna array, we calculate the constellation of the QPSK digital modulation scheme for a steered beam and study its angular dependency. Finally, we provide an upper bound for the efficiency of STC arrays.

Metasurface Superstrate Beam Steering Antenna with AMC for 5G/WiMAX/WLAN Applications

A beam-steering antenna based on non-uniform metasurface superstrate and artificial magnetic conductor (AMC), operating at 3.5 GHz, is proposed. The antenna can steer the beam along θ = −18° and 18° with the superstrate and along θ = 0° in the absence of the superstrate with almost zero scan loss. The proposed antenna structure consists of a top layer of non-uniform metasurface superstrate made of a 20 × 20 grid of electrically-small square-shaped metallic pixels while the bottom part consists of AMC with a grid of 5 × 5 pixels. The radiating element, CPW-fed monopole antenna, is placed between AMC and superstrate. The fabricated prototype shows desired beam steering in directions of θ = −18°, 0°, and 18° while maintaining uniform realized gain of 5.5 dBi and matching well with simulations.

A constant phase stable over the wideband for beam steering antenna applications

A K-band wideband self-compensating phase shifter based on gap waveguide is presented. The traditional waveguide phase shifter cannot easily achieve a stable phase shift over wideband due to the dispersion effect. Accordingly, a short-circuit structure and a slow-wave structure are designed in this paper, and their phase shifts show a positive-slope and a reverse-slope with respect to frequency. The two structures are realized using the tuning screw technology, and different phase shifts of 0–140° are realized by adjusting the number of screws. Besides, two structures are combined with a high-isolation power divider to realize a phase shifter with high phase and amplitude stability. The phase shifter is manufactured and measurement results of the eight phase shifts of the phase shifter show that the bandwidth of the phase changes within ±5° was greater than 30%. Finally, a four-way feeding network has been designed, which is used to form a four-element linear array. Generally, when the antenna beam is steered, the main-beam directions of different frequencies are not consistent. Therefore, by compensating the slope of the phase shifter with respect to the frequency, an array antenna whose main-beam direction does not change with respect to frequency is designed.

A Low-Cost Beam Steering Antenna for Indoor Wireless Communication

Low-cost beam coverage is one of the main goals of indoor wireless communication. We propose a low-cost beam steering (BS) antenna by using a hemispherical active frequency selective surface (AFSS) and its embedded varactors. At the same time, in the 3-D spherical coordinate system, we propose a universal design method for this type of antenna based on the principle of phase compensation. The designed BS antenna can realize energy gathering and beam switching in the quasi-full airspace on the ground. BS without phase shifter and reasonable allocation of energy brings the advantages of low cost. The proposed approach provides a feasible scheme for improving the robustness and energy saving of wireless communication.

Varactor-Based Phase Shifters Operating in Differential Pairs for Beam-Steerable Antennas

A concept of varactor-based phase shifter operating in differential pair for beam-steerable antennas is presented in this article. The basic phase-tuning unit consists of a microstrip transmission line and several shorted-stub-terminated varactors loaded on its edge. A pair of these phase-tuning units working in differential mode can achieve a full 360° phase shift, which allows a low loss and simple structure. An accurate equivalent circuit model for this phase shifter is developed for fast calculation allowing the design and optimization of the structure with a genetic algorithm (GA). A pair of phase-tuning units, each including three stub-loaded varactors, is identified as a practical solution to produce a continuously tunable phase difference nearly covering 0°–360°, with two symmetrical 11°-wide blind zones and a maximum insertion loss of 2.04 dB. A 1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times4$ </tex-math></inline-formula> beam-steerable dielectric resonator antenna (DRA) array is then designed, fabricated, and tested to demonstrate the practicality of the proposed phase shifter. The measured results illustrate that the array is able to continuously scan from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$- 45^\circ $ </tex-math></inline-formula> to 45°, with a tunable operating frequency band from 4.75 to 5.25 GHz. All these findings suggest that the proposed phase shifter concept is promising and practical to realize beam-scanning antennas.

Smart, Fast, and Low Memory Beam-Steering Antenna Configurations for 5G and Future Wireless Systems

Smart Antennas are important to provide mobility support for many enhanced 5G and future wireless applications and services, such as energy harvesting, virtual reality, Voice over 5G (Vo5G), connected vehicles, Machine-to-Machine Communication (M2M), and Internet of Things (IoT). Smart antenna technology enables us to reduce interference and multipath problems and increase the quality in communication signals. This paper presents a number of nonlinear configurations of dipole arrays for forming a single beam in any desired direction. We propose three, four, six, and eight-element array structures to perform this single beam-steering functionality. The proposed array configurations with multiple axes of symmetry (in the azimuthal plane) decrease the computational repetitions in optimizing respective weight factors for beam-steering. The optimized weight factors are obtained through the Least Mean Square (LMS) method. MATLABTM is used to calculate optimized weight factors as well as to determine the resulting radiation patterns. Since antennas are bidirectional elements, beamforming in one direction means that the antenna will also have high receiving gain in that direction. Performances of differently configured models are compared in terms of their directivity, sidelobe reduction, and computational complexities for beam-steering.

Experimental demonstration of dispersion-diversity multicore fiber optical beamforming.

Phased array antenna (PAA) beam-steering in high radiofrequency bands will be key for upcoming 5G & Beyond wireless communications systems. As a compact and efficient solution to provide tunable beam steering simultaneously to parallel antenna distribution and connectivity, we experimentally demonstrate, for the first time to our knowledge, tunable optical beamforming implemented on a dispersion-diversity multicore optical fiber. The uniqueness of this fiber lies in the fact that each one of its seven step-index trench-assisted cores has been tailored to provide the required chromatic dispersion to enable tunable optical true-time delay line operation. Continuous 1D beam-steering was demonstrated by measuring the radiating pattern of an in-house fabricated 8-element PAA in an anechoic chamber at the radiofrequency of 26 GHz, sweeping the beam-pointing angle from -43° up to 40° by varying the operating optical wavelength from 1542.50 up to 1548.28 nm. Next-generation fiber-wireless communications systems will benefit from the demonstrated dispersion-diversity MCF optical beamforming in terms of flexibility, versatility, capacity, and connectivity along with reduced size, weight, and power consumption.