Azimuth Plane Research Articles

A Pattern-Reconfigurable Antenna for Single-RF 5G Millimeter-Wave Communications

A millimeter-wave (mmWave) antenna with beam steering capability and a single feed is introduced. Fifth-generation (5G) systems with a single feed or a single radio frequency (RF) chain can provide inexpensive and energy-efficient solutions in applications such as the Internet of Things. The antenna consists of a half-wavelength dipole with a balun structure printed on both sides of a substrate and a parasitic pixel surface in front of the dipole. The antenna achieves beam-steering in the azimuth plane by controlling two diodes that alter the connections in the parasitic surface. Phase shifters or multiple feeds are not required to control the beam angle and therefore the antenna can support single-RF 5G operation. By introducing proper objective functions, the connections of the parasitic surface and locations of the two diodes can be optimized with the genetic algorithm. The ground plane and dc bias lines are printed on the backside of the substrate. Simulation and experimental results show that the proposed single port pattern reconfigurable antenna can operate in the 26–30 GHz mmWave bands. The realized gain of 7.96 dBi and two radiation patterns with peak gains directed to 75 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> and 110 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> are verified by experiment demonstrating the feasibility of the proposed design concept.

Risley-Prism-Based Dual-Circularly Polarized 2-D Beam Scanning Antenna With Flat Scanning Gain

Although the two-dimensional (2-D) beam scanning antenna based on the Risley-prism (R-P) principle has been proposed, the previous research mainly used linear phase progression phase-shifting surfaces, which has the problem that the gain decreases rapidly when the beam scans to a large angle in the elevation plane. Here, exponential phase gradient phase-shifting surfaces based on the Risley-prism principle are innovatively proposed, which can realize the flat scanning gain of 2-D beam scanning antenna. In addition, a rotatable polarization control surface is introduced to make the proposed 2-D beam scanning antenna work in dual-circular polarization. The experimental results show that the maximum scanning angle of the antenna is 52° in the elevation plane and 360° in the azimuth plane. In particular, the gain variation of the beam is only 0.6 dB within elevation angle 45°, showing a flat scanning gain characteristic.

A planar wideband 2‐D beam‐forming network for multibeam application

This article presents a wideband 2-D beam-forming network (BFN) utilizing a three-layer strip-line structure, which has 16 input ports and 16 output ports. The BFN, composed of multiple 2-D couplers, crossovers, and phase shifter groups, can provide an equal power signal distribution with ±45° or ±135° phase differences between the adjacent output ports, hence achieving 2-D beam scanning in both azimuth and elevation planes. To validate the concept, a prototype operating in the frequency range of 2.25–3.75 GHz is fabricated, measured, and discussed. The measurement results coincide well with the simulation ones.

Radiation pattern reconfigurable graphene plasmonics-based nanoantenna

We report a full-wave analysis of a graphene-based plasmonic nanoantenna with frequency and pattern reconfigurable characteristics. The proposed antenna consists of a circular graphene patch and four graphene fan-shaped parasitic elements. Ten different operational states of radiation patterns can be obtained by controlling the conductivity of parasitic elements. The main beam is rotated from −45 deg to +45 deg with a step increment of 90 deg in the azimuth plane. The resonance frequency for different operational states slightly varies from 2.43 to 2.47 THz with almost stable radiation performance. Simulated gain has been achieved up to 4.68 dBi with a total efficiency of 62%. The proposed antenna supports the surface plasmon waves; hence it can be successfully miniaturized at the THz frequencies. The simulated results for return loss, gain, and radiation patterns have been reported for 10 different operational states.

Synthesis of novel 8 × 8 beam‐forming network for broadband multibeam antenna array

Synthesis of a novel 8 × 8 beam-forming network (BFN) for broadband multi-beam antenna arrays in the X-band has been proposed. The synthesized BFN has 6 less path crossings than a classic Butler matrix. The BFN design is realized using basic elements such as slot-line transition and magic-Ts. A numerical simulation for the analysis of the frequency characteristics of the proposed BFN is carried out. In addition, we offer a design of an eight-channel multibeam antenna array consisting of the synthesized BFN and Vivaldi antennas. Eight spatial beams cover approximately 120° in the azimuth plane with a peak gain of 12 dB in the range of 8.3–11.7 GHz. The proposed broadband multibeam antenna array has good performance, compactness, and ease of fabrication that would be an attractive candidate for radar, satellite communication, and wireless computer networks.

Design of Quad feed end-fire microstrip patch antenna for Airborne Systems

To design a quad feed end-fire microstrip patch antenna for airborne systems. Basically these type of antennas are most helpful for avoiding mid-air collisions between aircraft. The microstrip patch antenna is very small in size and it is less in weight. Due to small size and less weight, it offers an easy design and fabrication process. The microstrip patch antenna has radiating patch on one side and ground on the other side. They operate at microwave frequencies. The low profile structure of microstrip antenna offers its wide use in wireless communication. They are used as communication antenna on missiles. Traffic alert and Collision Avoidance System (TCAS) is an airborne system which is utilized to provide the service as last defense equipment for avoiding mid-air collisions between the aircraft. 1.03 GHz and 1.09 GHz are the transmitting and receiving frequencies of the existing TCAS antenna respectively. In airborne systems, low aerodynamic drag is required. FR4 epoxy is chosen as the substrate material whose dielectric constant is 4.4. 1.06GHz is chosen as the design frequency, since it is centre frequency between 1.03GHz and 1.09GHz. Microstrip patch antenna always radiates in the broadside direction which is along elevation plane. Due to metallic cap, microstrip patch antenna can also radiate in the end fire radiation which is along the azimuth plane. The ground plane must have very large dimensions than the patch. This microstrip patch antenna working at UHF (Ultra High Frequency) band is designed and their parameters like gain, directivity, return loss, VSWR (Voltage Standing Wave Ratio) and radiation pattern have been analyzed and simulated using ANSYS HFSS (High Frequency Structure Stimulator).

Research and Modeling of Digital Antenna Arrays with Directional Elements on Azimuth-Elevation in VHF Terrain and Vegetation Multipath Propagation Situations

In the paper the problem of using digital antenna arrays equipped with dipole and directive elements simultaneously in the azimuthal and elevation planes is discussed. In particular, they are investigated for communication channels of the VHF range below 1 GHz. This range is characterized by the fact that it has found wide distribution. However, its application is fraught with many difficulties, such as attenuation, reflection from rough surfaces, etc. One of the solutions to these problems can be azimuth-elevation digital beamforming. The paper presents the simulation results for the propagation of signals in the VHF range in free space, two-ray ground-reflection and foliage models. It is assumed that a symmetrical dipole is used on the transmitting side, and a directional Yagi antenna on the receiving digital antenna array (DAA) also equipped with a dipole. The circular (CAA) and hemi-dodecahedron shapes of the arrangement of elements of the receiving digital antenna array are simulated. The bit error rates (BER) depending on the distance between the transmitter and the receiver are estimated for the three above mentioned cases.

Monopulse antenna array based on three-modes with orthogonal radiation beams

A compact multi-layer substrate integrated waveguide (SIW) monopulse antenna array operating at X-band is proposed. The structure consists of four stacked layers, including one layer for the radiating 4 × 4 rectangular microstrip antenna elements and two SIW layers for the comparator network. The sum and difference modes provide orthogonal radiation patterns in the azimuth and elevation planes. The two SIW layers of the comparator network feature a compact multi-feed design while maintaining high isolation between the antenna ports. To validate the proposed antenna concept, silmulations and measuremets are carried out. The obtained resuts show good performnces, a −10-dB impedance bandwidth of 13.45 % (9.35–10.7 GHz) for the sum and difference ports, better than 30 dB isolation between the antenna ports, the difference radiation patterns better than −38 dB null-depth. The comparison between the simulated and measuremed results shows a good agreement.

Radial Basis Function for Breast Lesion Detection from MammoWave Clinical Data.

Recently, a novel microwave apparatus for breast lesion detection (MammoWave), uniquely able to function in air with 2 antennas rotating in the azimuth plane and operating within the band 1–9 GHz has been developed. Machine learning (ML) has been implemented to understand information from the frequency spectrum collected through MammoWave in response to the stimulus, segregating breasts with and without lesions. The study comprises 61 breasts (from 35 patients), each one with the correspondent output of the radiologist’s conclusion (i.e., gold standard) obtained from echography and/or mammography and/or MRI, plus pathology or 1-year clinical follow-up when required. The MammoWave examinations are performed, recording the frequency spectrum, where the magnitudes show substantial discrepancy and reveals dissimilar behaviours when reflected from tissues with/without lesions. Principal component analysis is implemented to extract the unique quantitative response from the frequency response for automated breast lesion identification, engaging the support vector machine (SVM) with a radial basis function kernel. In-vivo feasibility validation (now ended) of MammoWave was approved in 2015 by the Ethical Committee of Umbria, Italy (N. 6845/15/AV/DM of 14 October 2015, N. 10352/17/NCAV of 16 March 2017, N 13203/18/NCAV of 17 April 2018). Here, we used a set of 35 patients. According to the radiologists conclusions, 25 breasts without lesions and 36 breasts with lesions underwent a MammoWave examination. The proposed SVM model achieved the accuracy, sensitivity, and specificity of 91%, 84.40%, and 97.20%. The proposed ML augmented MammoWave can identify breast lesions with high accuracy.

Two-dimensional shear rate field and flow structures of a pseudoplastic fluid in a stirred tank using particle image velocimetry

For non-Newtonian fluids, an accurate determination of the shear rate is essential to optimize process parameters, which can lead to the improvement of the process efficiency. This work proposes the evaluation of an aqueous solution of carboxymethylcellulose (CMC) analyzing two azimuthal planes, AZ 0° and 45°, and four blade positions, AR 0°, 22.5°,45° and 67.5°, by ensemble-averaged and angle-resolved PIV measurements, respectively, in a stirred tank equipped with a pitched-turbine impeller. Results are shown in terms of time-averaged velocity, shear rate, apparent viscosity and Reynolds number fields. Differences between both PIV measurements approaches were significant in terms of velocity magnitude and characteristics of trailing vortices. The results demonstrate that the shear rate is strongly influenced by spatial resolution. The highest shear rates were obtained in the impeller region. The presence of a vortex above the blade resulted in high values of local Reynolds number, reflecting the presence of turbulence in that region.

A compact ultra‐wideband receiving antenna for monitoring applications

AbstractIn this paper, a compact ultra‐wideband receiving antenna is proposed. It consists of a top loaded planar monopole and a circular ground plane. This design combines various techniques such as the comb shaped top loading and the integrated lumped elements to effectively reduce the antenna size, while keeping a wide bandwidth and a reasonable realized gain. The proposed antenna operates across a wide frequency range from 20 to 8 GHz (for S11 &lt;−6 dB), occupies a compact volume of 500 × 500 × 340 mm3 (0.033λ0 × 0.033 λ0 × 0.023 λ0 at 20 MHz) and has a stable omnidirectional radiation pattern in azimuth plane from 20 to 6 GHz. Simulations and measurements are conducted to validate the antenna performance. It is demonstrated that this antenna is well suited to a variety of wideband radio frequency receivers for monitoring use.

2D Optical Phased Arrays for Laser Beam Steering Based On 3D Polymer Photonic Integrated Circuits

We propose a novel concept for the implementation of 2-dimensional (2D) optical phased arrays (OPAs) with end-fire waveguides as antenna elements (AEs), and we present its theoretical model and experimental proof. The concept is based on the use of 3-dimensional (3D) photonic integrated circuits (PICs) with multiple waveguiding layers on the PolyBoard platform. In their simplest form, the 3D PICs comprise AEs at different layers, vertical and lateral couplers for the distribution of light among the AEs, and phase shifters for the execution of the 2D beam scanning process. Using the field equivalence principle, we model the radiated field from the single-mode waveguide of the platform at 1550 nm, and we find that the expected beam width is 12.7°. We also investigate the perturbation that is induced into propagating fields inside parallel waveguides in proximity, and we conclude that waveguide spacings down to 6 µm can be safely used for development of uniform OPAs in the PolyBoard platform. For OPAs with 6 µm pitch and 4 AEs, we find that the maximum steering angle is 14.0° and the expected angular clearance, wherein the main radiation lobe is higher than any grating lobe by at least 3, 6 and 10 dB is 10.8°, 7.6° and 2.8°, respectively. Based on our simulations, we design and fabricate single- and 2-layer PICs with 1 × 4 and 2 × 4 OPAs. The lateral pitch of the OPAs ranges from 10 down to 6 µm, while the vertical pitch is 7.2 µm. We experimentally characterize these OPAs and validate the potential of the 2-layer PICs for 2D beam scanning on the azimuthal and elevation plane. The beam profiles and the main scanning parameters such as the maximum steering angle and the relative intensity between the main and the grating lobes are found in excellent agreement with our simulations.

Proof of Concept Novel Configurable Chipless RFID Strain Sensor.

This paper contains two main areas of research: First, this work outlines a novel, highly sensitive strain sensor design that should support various levels of deformation, depending on the substrate type used. Physical implementations in this work have focused on proving its large deformation capabilities, and simulations have been used to assess its more general electromagnetic response. The other part of this paper focusses on exploring other effects that will impact the sensing of strain of resolutions below 10 με, which is a capability achieved by other aerospace-grade strain sensor technologies. These effects are limited to mechanical swelling and sensor orientation in the azimuth and elevation planes, as these appear to be unexplored and highly relevant issues to the topic of chipless RFID-based strain sensing. From this exploration, it is apparent that the effects of mechanical swelling and sensor orientation (amongst others) will need to be addressed in any real-life implementation of the sensor, requiring a strain resolution below 10 με.

Electrically Small, Planar, Horizontally Polarized Dual-Band Omnidirectional Antenna and Its Application in a MIMO System

A method of designing a miniature planar dual-band horizontally polarized (HP) omnidirectional antenna is presented. It combines an electrically small (ES) lower band omnidirectional loop antenna with an upper band Alford loop antenna on a single substrate. Its frequency ratio is higher than two. A technique that effectively increases the bandwidth of the Alford loop is developed. To reduce the gain variation in the azimuthal plane, the ES loop is fed by four symmetrical radial strips extended from a circular patch. For demonstration, the ES loop and Alford loop were designed for the 2.4 and 5 GHz Wi-Fi bands for Wi-Fi applications. The antenna prototype has a diameter of 0.296λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> and a height of 0.012λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> only, where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the wavelength in air at the lowest operating frequency. It covers the Wi-Fi bands of 2.4-2.5 and 5.1-5.9 GHz, with a high total efficiency of ~90%. Based on the single-element design, a four-element multiple-input-multiple-output (MIMO) antenna is developed for Wi-Fi applications. The MIMO antenna has a size of 0.93×0.93×0.012λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , with a small gain variation of less than 3.2 dB in the azimuthal plane. The isolations between any two antenna elements are higher than 16 and 24.5 dB for the 2.4 and 5 GHz bands, respectively.

Vortex breakdown control using varying near axis swirl

In this paper, the Vogel–Escudier flow is studied at an aspect ratio of 2.5 and a Reynolds number range of 330–3000. An attempt is made to control the vortex breakdown bubbles using a thin rod in co- and counter-rotation cases. The flow is studied qualitatively using planar laser-induced fluorescence and quantitatively using particle image velocimetry measurements. In terms of swirl strength, defined as the ratio of Reynolds numbers of the disk and control rod, a complete suppression and subsequent reemergence of vortex breakdown bubbles is observed at 56 and 37, respectively. Counter-rotation shows a slight decrease until −150 and a periodic and aperiodic shedding of the vortices at −112 and −75. An attempt is made to explain the flow behavior by experimental and analytical means taking into consideration the azimuthal plane flow using the swirl decay mechanism. Further, experiments are performed for time varying co- and counter-rotations for various combinations of amplitude and frequency. The anomalous behavior at high frequencies of destabilization of vortices in co-rotation and a milder change in counter-rotation is observed.

Chiral polarization textures induced by the flexoelectric effect in ferroelectric nanocylinders

Polar chiral structures have recently attracted much interest within the scientific community, as they pave the way towards innovative device concepts similar to the developments achieved in nanomagnetism. Despite the growing interest, many fundamental questions related to the mechanisms controlling the appearance and stability of ferroelectric topological structures remain open. In this context, ferroelectric nanoparticles provide a flexible playground for such investigations. Here, we present a theoretical study of ferroelectric polar textures in a cylindrical core-shell nanoparticle. The calculations reveal a chiral polarization structure containing two oppositely oriented diffuse axial domains located near the cylinder ends, separated by a region with a zero-axial polarization. We name this polarization configuration "flexon" to underline the flexoelectric nature of its axial polarization. Analytical calculations and numerical simulation results show that the flexon's chirality can be switched by reversing the sign of the flexoelectric coefficient. Furthermore, the anisotropy of the flexoelectric coupling is found to critically influence the polarization texture and domain morphology. The flexon rounded shape, combined with its distinct chiral properties and the localization nature near the surface, are reminiscent of Chiral Bobber structures in magnetism. In the azimuthal plane, the flexon displays the polarization state of a vortex with an axially polarized core region, i.e., a meron. The flexoelectric effect, which couples the electric polarization and elastic strain gradients, plays a determining role in the stabilization of these chiral states. We discuss similarities between this interaction and the recently predicted ferroelectric Dyzaloshinskii-Moriya interaction leading to chiral polarization states.

Single and double scattering mechanisms in ionization of helium by electron vortex projectiles

Triple differential cross sections (TDCSs) for electron vortex projectile ionization of helium into the azimuthal plane are calculated using the distorted wave Born approximation. In this collision geometry, the TDCSs at low and intermediate energies exhibit unique qualitative features that can be used to identify single and double scattering mechanisms. In general, our results predict that the ionization dynamics for vortex projectiles are similar to those of their non-vortex counterparts. However, some key differences are observed. For non-vortex projectiles, a double scattering mechanism is required to emit electrons into the azimuthal plane, and this mechanism becomes more important with increasing energy. Our results demonstrate that for vortex projectiles, emission into the azimuthal plane does not require a double scattering mechanism, although this process still significantly influences the shape of the TDCS at higher energies. At low projectile energies, non-vortex ionization proceeds primarily through single binary collisions. The same is generally true for vortex projectiles, although our results indicate that double scattering is also important, even at low energy. Vortex projectiles have an inherent uncertainty in their incident momentum, which causes a broadening of the binary peak at all energies and results in a splitting of the binary peak at higher energies. The results presented here lead to several predictions that can be experimentally tested.

Beam‐steering lens antenna for point to multipoint communications at 28 GHz band

In this article, we propose a new design of a multibeam cylindrical Luneburg lens antenna designed in the 28 GHz band. The proposed antenna is based on the parallel plate waveguide technique, in which the plates are separated by a fixed spacing and a homogenous dielectric material is applied between the plates. The most intuitive advantage of the proposed lens against the previous ones is the simplicity of the lens profile and volume, which is essential for the whole design and manufacturing processes for high-frequency applications. In addition, it provides a cost-effective and simple mechanical assembly. To reduce the losses associated with the feed elements, the lens is excited by an array of simple and compact integrated waveguide elements. The measured results show that the proposed antenna achieves a maximum gain of 17.73 dB and a maximum beam steering angle of 57.7° in the azimuth plane. Furthermore, the measured gain of the antenna varies by only 1 dB over the entire beam steering rang and the measured side lobe level of the antenna is less than −12.2 dB.

Ear-Specific Hemispheric Asymmetry in Unilateral Deafness Revealed by Auditory Cortical Activity.

Profound unilateral deafness reduces the ability to localize sounds achieved via binaural hearing. Furthermore, unilateral deafness promotes a substantial change in cortical processing to binaural stimulation, thereby leading to reorganization over the whole brain. Although distinct patterns in the hemispheric laterality depending on the side and duration of deafness have been suggested, the neurological mechanisms underlying the difference in relation to behavioral performance when detecting spatially varied cues remain unknown. To elucidate the mechanism, we compared N1/P2 auditory cortical activities and the pattern of hemispheric asymmetry of normal hearing, unilaterally deaf (UD), and simulated acute unilateral hearing loss groups while passively listening to speech sounds delivered from different locations under open free field condition. The behavioral performances of the participants concerning sound localization were measured by detecting sound sources in the azimuth plane. The results reveal a delayed reaction time in the right-sided UD (RUD) group for the sound localization task and prolonged P2 latency compared to the left-sided UD (LUD) group. Moreover, the RUD group showed adaptive cortical reorganization evidenced by increased responses in the hemisphere ipsilateral to the intact ear for individuals with better sound localization whereas left-sided unilateral deafness caused contralateral dominance in activity from the hearing ear. The brain dynamics of right-sided unilateral deafness indicate greater capability of adaptive change to compensate for impairment in spatial hearing. In addition, cortical N1 responses to spatially varied speech sounds in unilateral deaf people were inversely related to the duration of deafness in the area encompassing the right auditory cortex, indicating that early intervention would be needed to protect from maladaptation of the central auditory system following unilateral deafness.

Selective auditory attention modulates cortical responses to sound location change in younger and older adults.

The present study measured scalp potentials in response to low-frequency, narrowband noise bursts changing location in the front, azimuthal plane. At question was whether selective auditory attention has a modulatory effect on the cortical encoding of spatial change and whether older listeners with normal-hearing thresholds would show depressed cortical representation for spatial changes relative to younger listeners. Young and older normal-hearing listeners were instructed to either passively listen to the stimulus presentation or actively attend to a single location (either 30° left or right of midline) and detect when a noise stream moved to the attended location. Prominent peaks of the electroencephalographic scalp waveforms were compared across groups, locations, and attention conditions. In addition, an opponent-channel model of spatial coding was performed to capture the effect of attention on spatial-change tuning. Younger listeners showed not only larger responses overall but a greater dynamic range in their response to location changes. Results suggest that younger listeners were acquiring and encoding key spatial cues at early cortical processing areas. On the other hand, each group exhibited modulatory effects of attention to spatial-change tuning, indicating that both younger and older listeners selectively attend to space in a manner that amplifies the available signal.NEW & NOTEWORTHY In complex acoustic scenes, listeners take advantage of spatial cues to selectively attend to sounds that are deemed immediately relevant. At the neural level, selective attention amplifies electrical responses to spatial changes. We tested whether older and younger listeners have comparable modulatory effects of attention to stimuli moving in the free field. Results indicate that although older listeners do have depressed overall responses, selective attention enhances spatial-change tuning in younger and older listeners alike.