Conformal Phased Array Antenna Research Articles

A Subarray Selection Scheme for Cellular-Connected UAV With Conformal Phased Array Antenna

A Subarray Selection Scheme for Cellular-Connected UAV With Conformal Phased Array Antenna

A Tiling Method for Sub-Arrayed Spherical Conformal Phased Array Antennas Based on Maximum 3-D Space Entropy Model

A Tiling Method for Sub-Arrayed Spherical Conformal Phased Array Antennas Based on Maximum 3-D Space Entropy Model

Dual-Band Omni-Directional Scanning Conical Conformal Phased Array Antenna

Dual-Band Omni-Directional Scanning Conical Conformal Phased Array Antenna

A Bendable Wideband Dual-Polarization Conformal Phased-Array Antenna

In this letter, we proposed a bendable wideband dual-polarization low-profile conformal phased array antenna. The antenna element is an Invert-F fed stacked-patch antenna. It provides an active VSWR < 3 for 10.7 GHz to 12.75 GHz in the principal planes. The proposed phased array antenna employs a row modular architecture, which enables it to bend to a cylindrical geometry. Both the antenna aperture and the active components of the conformal phased array antenna are considered for bending in the letter. A prototype conformal phased array antenna with 8 rows of 4 dual-polarization antenna element was fabricated, assembled and measured. Wide-angle beam scanning is achieved by electronically scanning along the curved axis of the cylindrical conformal phased array antenna. Moreover, there is no grating lobe when scanning down to 60°.

A Conformal Phased Array Antenna with Improved Gain on a Cylindrical Surface

The manuscript reports phase compensation technique for improving the directionality and gain of a conformal phased array antenna on a cylindrical surface while steering the beam. The investigation reports two different components of phase compensation required for enhancing the directionality: (i) compensation required to mitigate the effect due to the vertical displacements of antenna elements on the conformal surface and (ii) additional phase shift required to align the broadside of each element in the direction of scan angle. It is highly effective in the restoration of the beam of a phased array mounted on conformal surfaces of a smaller radius causing significant deformation in the radiation pattern. The proposed formulation is implemented through Matlab and verified using CST for a 1-D circumferential phased array with 7 elements of a rectangular patch antenna of dimensions L = 8.72 mm and W = 14.52 mm designed for 10 GHz on a cylindrical surface of 10 cm radius. The model is also applicable to a Concave conformal phased array and can be extended to 2-D arrays. To the best of our knowledge, this is the first report on such a study and will find direct applications in the design and development of conformal phased arrays with high directionality and gain.

Millimeter-Wave Wide-Angle Scanning Phased Array Antenna Based on Heterogeneous Beam Elements

By imitating the element inclined beam distribution of a curved surface conformal (CSC) phased array antenna (PAA), a pseudo-curved surface conformal (PCSC) PAA realizes wide-angle scanning while maintaining a planar low profile. Inspired by the PCSC PAA, this communication proposes a PAA based on heterogeneous beam elements (HBEs) to realize wide-angle scanning. Using HBEs introduces a new design degree of freedom (DoFs), namely the element beam shape, to PAA. By optimizing HBEs and their arrangement, the effective aperture of a PAA can be increased at large scanning angles, and thus the scanning range can be improved. To verify the idea, first, a wide-beam 1×4-element subarray is developed. Then, a standard 4×4-element PAA is implemented using four uniform 1×4-element subarrays, achieving a >±60° 3-dB gain variation scanning range. At last, based on the standard PAA, by adjusting its structure to tailor four subarrays’ beam inclinations, a 4×4-element HBE PAA is designed. It further improves the scanning range to >±70° at an average cost of ~1.5dBi broadside scanning gain within the 5G mmWave band (24.25-29.5GHz, 19.5%). To the authors’ best knowledge, compared with the former planar mmWave PAAs, the proposed design shows the widest scanning range in a wide bandwidth.

Low profile conformal phased array with wide scanning range

AbstractA linearly polarized conformal phased array antenna with a low profile and a large scanning range is proposed, based on stacked patch antenna element fed by a coupled microstrip line. A backed compact cavity is designed in the antenna element, to reduce the mutual coupling between the elements. The prototype of the proposed conformal array, a conformal array composed of 4 × 4 elements which are axially mounted onto a cylindrical surface, is fabricated and measured, whose profile is as low as 0.072 λh (λh is the free‐space wavelength at the highest operating frequency). The experimental results demonstrate that the array achieves active VSWR below than 2.5 over the frequency band of 1.52–1.77 GHz (15%), within the wide‐scanning ranges of ±70° in the E plane and ±60° in the H plane, and the measured results are in good accordance with the calculation.

Millimeter-Wave 1-D Wide-Angle Scanning Pseudo-Curved Surface Conformal Phased Array Antennas Based on Elongated Planar Aperture Element

To perform wide-angle scanning while maintaining a planar low profile, we propose a new kind of millimeter-wave (mmWave) planar phased array antenna using inclined beam elements to imitate a curved surface conformal (CSC) array, called a pseudo-curved surface conformal (PCSC) phased array antenna. We present the concept of our PCSC phased array and then design an elongated planar aperture antenna (EPAA) element, achieving stable high broadside gain and wide beam on the scanning plane within a wide bandwidth. Then, by introducing asymmetries to the EPAA element, the beam inclination of the EPAA element can be adjusted. Accordingly, we use EPAA elements with different beam inclinations to form a 1 × 4-element 1-D wide-angle scanning PCSC phased array antenna. We design, fabricate, and measure a prototype of our proposal, with measured results showing that the proposed design has a 3 dB gain variation across a scanning range of more than ±62° (and as high as ±68°) within the 5G mmWave band (24.25 to 29.5 GHz), which is about ±10° better than its traditional counterpart.

Millimeter-Wave Wideband Wide-Angle Scanning Proactive Conformal Phased Array Antenna

Though conformal phased array antennas have better wide-angle scanning capability than their traditional planar counterparts do, their fabrication is generally complex. Therefore, this letter presents a millimeter-wave (mmWave) proactive conformal (PC) phased array antenna (PAA) formed by high-low alternate elements/subarrays to proactively modulate the array aperture, achieving wide-angle scanning and easy fabrication. A 1×6-element endfire high-gain low sidelobe level subarray is designed, based on which a 4×6-element PC PAA is implemented. The measured results show that the reflection coefficient of the fabricated prototype is mostly <−10 dB, the port isolation is >18 dB, the endfire scanning gain is >15.5 dBi, and the 3-dB gain variation scanning range is >±60° with a peak up to ±68° within 24.25–29.5 GHz (19.5%).

Wing Conformal Load-Bearing Endfire Phased Array Antenna Skin Technology

In this article, a phased array antenna skin is proposed for conformally assembling scenarios and wide scanning applications. Planar inverted F antenna (PIFA) is used as a radiation element of the proposed array due to its low profile and omnidirectional radiation pattern. The PIFA element is conformally assembled in a wing of an aircraft and is designed and fabricated with the technology of composite material, which makes the PIFA element load bearing. The endfire beam synthesis is also investigated, and the proposed array supports wide-angle beam scanning in both forward and backward regions. An array of 240 PIFA elements are designed, simulated, fabricated, and experimentally tested. The fabricated sample is able to bear an overload of 1 g in the mechanical test, and all the electronic experiment results agree well with the simulation data.

A Composite Right/Left-Handed Phase Shifter-Based Cylindrical Phased Array with Reinforced Particles Responsive to Magneto-Static Fields

A conformal cylindrical phased array antenna excited with composite right/left-handed (CRLH) phase shifters is proposed. The phase tuning of the CRLH phase shifter is achieved by embedding novel magneto-static field-responsive micron-sized particles in its structure. It is shown that through the tiny magnet activation of these novel magneto-static particles at appropriate locations along the length of CRLH stub and inter-digital fingers, variable phase shifts are obtained. The proposed particle-based CRLH phase shifter operates in C-band (5–6) GHz with a low insertion loss and phase error. The 1 × 4 cylindrical phased array is excited with the four unit cells of the proposed particle-embedded CRLH transmission line phase shifters to scan the main beam at desired scan angles. A prototype of a 1 × 4 cylindrical phased array excited with the particle-based CRLH phase shifters was fabricated, and the results show that the simulated results are in close agreement with the measured results. The conformal cylindrical array with the proposed particle-based CRLH phase shifters has great potential for use in printed and flexible electronics design where commercially available phase shifters have a definite drawback.

Beamforming with 1 × N Conformal Arrays.

The rapid growth of wireless spectrum access through cellular and IoT devices, for example, requires antennas with more capabilities such as being conformal and self-adapting beamforming. In this paper, the adaptive beamforming patterns of microstrip patch antenna arrays on changing flexible (or conformal) curved surfaces are developed by deriving array coefficients based on the projection method that includes the mutual coupling between elements. A linear four-element microstrip patch antenna array is then embedded on two deformed conformal surfaces to investigate the projection method for desired beamforming patterns. The generated beamforming radiation patterns using the computed weighting coefficients are validated with theoretical equations evaluated in MATLAB, full-wave simulations in HFSS and measurement results. The measured results of the fabricated system agree with the simulated results. Furthermore, new guidelines are provided on the effects of mutual coupling and changing conformal surfaces for various beam-forming patterns. Such demonstrations pave the way to an efficient and robust conformal phased-array antenna with multiple beam forming and adaptive nulling capabilities.

2–18 GHz balanced antipodal Vivaldi conformal phased array antenna with resistive load and shorting posts

In this paper, a 2–18 GHz balanced antipodal Vivaldi conformal phased array antenna is proposed. Firstly, the conformal array achieves a low profile of 0.11λLow by using the tightly coupling mechanism. Here, the gap-induced element resonance (GIER) and the common mode resonance occur in the operating band, limiting the impedance bandwidth. Thus, the resistors are loaded to eliminate the GIER by suppressing the resonant current. Furthermore, the shorting posts are used to remove the common mode resonance by decreasing the resonant length. A transition structure between the stripline (SL) and the ground coplanar waveguide (GCPW) is designed to feed the antenna. The simulated results show that the array achieves a 9:1 bandwidth (2–18 GHz) for active VSWR <2.5 at broadside. Besides, the active VSWR is less than 2.5 for ±60° scanning in E-plane and 3.8 for ±45° scanning in H-plane. A 12 × 8 array prototype is fabricated and measured to validate the performance of the array. The measured results show a good agreement with the simulation.

Ultra-Wide-Scanning Conformal Heterogeneous Phased Array Antenna Based on Deep Deterministic Policy Gradient Algorithm

This article investigates the pattern synthesis of the conformal phased array antenna (PAA) by using the deep deterministic policy gradient (DDPG) algorithm, and a nearly full solid angle for beam steering is realized. The beam steering capability of the planar and conformal PAAs is theoretically compared at first, and a conclusion is obtained that conformed to the conical-and-cylindrical structure can help to achieve ultrawide-angle beam steering. Next, a typical deep reinforcement learning algorithm, which is the DDPG algorithm, is utilized to deal with the fast beam steering problem of the conformal heterogeneous PAA. By virtue of the strong fitting ability of the DDPG algorithm for high-dimensional continuous nonlinear problems, the performance of fast beam steering is achieved within a wide-angle range within (−150°, 150°). Finally, a prototype of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\times17$ </tex-math></inline-formula> conformal PAA is fabricated for measurement and verification, and the measured results are in good agreement with the simulation results.

Cognitive Conformal Antenna Array Exploiting Deep Reinforcement Learning Method

A cognitive antenna array, which is designed by using deep reinforcement learning (DRL) is proposed in this article to adapt to the complex electromagnetic environment. Specifically, the phased array antenna is utilized as the manipulatable component to achieve the characteristic of beam steering with the help of the DRL algorithm. We begin by establishing a DRL-based framework, which is comprised of a microprogrammed control unit, power divider, digital phase shifter, and the patch antenna array. In the DRL algorithm, the desired beam steering is obtained through trial-and-error interactions with the environment, which is required to observe predefined rewards based on the current state and action. Next, the system is trained to perform beam steering, and a set of hyperparameters of the deep neural network are obtained and stored for practical usage. A good agreement is achieved between the simulated and measured radiation patterns of the planar phased array antenna, which validates the DRL-based phase distribution regulation algorithm. Finally, the algorithm is implemented in the design process of a conformal phased array antenna, and it is shown that the measured radiation performance of the array is satisfactory for different beam scan angles.

Beam Steering of Orbital Angular Momentum Vortex Waves With Spherical Conformal Array

In this letter, a spherical conformal antenna is designed, fabricated, and experimentally demonstrated to realize the beam steering of orbital angular momentum (OAM) vortex waves with hemisphere coverage. The theoretical formula of phase shift is deduced to design the conformal array antenna producing vortex radio waves with arbitrary beam direction. A prototype of a geodesic dome-based spherical conformal phased-array antenna is presented to validate the theoretical analysis. The experimental results verify that the hemispherical beam steering of OAM vortex waves can be effectively and flexibly generated. The proposed method can provide a reference for OAM vortex communication with full space coverage.

Height Reduced Concave Sector-Cut Spherical Conformal Phased Array Antenna Based on Distributed Aperture Synthesis

The conventional spherical conformal phased-array antenna (SPAA) has a wide beam coverage but suffers from a high profile due to its spherical conformal carrier. In this article, a low-profile conformal array antenna is modified from the conventional SPAA, which can be called the concave sector-cut spherical phased-array antenna (CSSPAA). A distributed aperture synthesis is employed to guarantee that the performance of the CSSPAA is close to that of the SPAA after reducing its height as much as possible. The CSSPAA’s height and the element’s half-power beamwidth (HPBW) are properly designed to minimize the blockage influence due to the special topology of the CSSPAA. A prototype CSSPAA with 48 elements is designed as an example, and the height of the CSSPAA is 43% lower than that of the SPAA with the similar performance in the hemispherical beam coverage. Both numerical and experimental results indicate the effectiveness of the developed method.

Conformal Phased Array Antenna for Unmanned Aerial Vehicle With ±70° Scanning Range

Conformal antennas are practicable candidates to the aerodynamic platforms. A wide-angle scanning conformal phased array antenna for an unmanned aerial vehicle (UAV) platform is designed and presented in this article. An eight-element linear phased array loaded with frequency selective surface (FSS) operating in S-band is investigated. The horizontally polarized antenna element is designed based on a tapered slot feeding dipole. The antenna aperture can be easily conformed to the front wing airframe of the UAV due to the flexibility of the employed polyimide film. To fulfill the requirement of the airborne communication system, two kinds of FSSs are loaded on the dipole antenna to enhance the gain and reduce the 3 dB beamwidth of the main lobe in the elevation plane. To improve the active impedance matching when the beam scans to the large angles, a novel parasitic structure is proposed. Finally, a 1 ×8 linear conformal array prototype is simulated, fabricated, and measured. The experimental results indicate that the antenna array achieves a fractional bandwidth of 22.1% with ±70° scanning along the E-plane. The measured results validate the performance of the proposed conformal array and the design.

Inkjet-Printed Graphene-Based 1 × 2 Phased Array Antenna.

Low-cost and conformal phased array antennas (PAAs) on flexible substrates are of particular interest in many applications. The major deterrents to developing flexible PAA systems are the difficulty in integrating antenna and electronics circuits on the flexible surface, as well as the bendability and oxidation rate of radiating elements and electronics circuits. In this research, graphene ink was developed from graphene flakes and used to inkjet print the radiating element and the active channel of field effect transistors (FETs). Bending and oxidation tests were carried out to validate the application of printed flexible graphene thin films in flexible electronics. An inkjet-printed graphene-based 1 × 2 element phased array antenna was designed and fabricated. Graphene-based field effect transistors were used as switches in the true-time delay line of the phased array antenna. The graphene phased array antenna was 100% inkjet printed on top of a 5 mil flexible Kapton® substrate, at room temperature. Four possible azimuth steering angles were designed for −26.7°, 0°, 13°, and 42.4°. Measured far-field patterns show good agreement with simulation results.

Wide-Scanning Conformal Phased Array Antenna for UAV Radar Based on Polyimide Film

Polyimide film is a practicable alternative to the conventional substrates utilized in conformal antennas. Due to its flexibility, the antennas based on the polyimide film can be easily conformed to the platform surface. An eight-element linear-phased array operating at the P-band with a wide scan angle is investigated in this letter, which is constructed by the dipoles printed on the polyimide film. The antenna surface is mounted on the front wing of an unmanned aerial vehicle (UAV). Strong coupling is observed between the array elements when the beam scans. Therefore, decoupling structures are loaded in the array elements to broaden the scan angle. To satisfy the requirement of the radar system, directors and reflectors are also employed on the surface of the front wing to narrow the main lobe beamwidth in the elevation plane. The proposed phased array achieves a fractional bandwidth of 16.7% when scanning up to ±60° in the E-plane. The validity of this design is verified by the simulation and measurements of a 1 × 8 array prototype.