Reconfigurable Pattern Research Articles

Pattern reconfigurable dielectric resonator antenna based on phased array switches

This study examines a cuboid dielectric resonator antenna with partial ground plane. The dielectric resonator of the antenna is designed with high permittivity, ɛr=30. The dimension used to design this cuboid dielectric resonator antenna was based on the dielectric waveguide model (DWM). Meanwhile, the feeding structure depends on the microstrip feed line that resides above the FR4 substrate. The significance of this study is to obtain a reconfigurable radiation pattern. Switches were used to operate the two array elements with phased control in order to obtain reconfigurable pattern, by controlling the switches, the results produced three different radiation patterns at 2.6 GHz with total efficiency 88%. Hence, this proposed antenna can be used for Long Term Evolution (LTE) of band 7 and band 38 with an impedance bandwidth of more than 200 MHz. This study was implemented in a CST Microwave Studio.

Toward service selection for workflow reconfiguration:An interface-based computing solution

Due to the open and diverse features of the Internet, applications need an effective method of performing a workflow reconfiguration to achieve both the functional behaviors and non-functional requirements of workflow changes when a service failure occurs. This paper proposes a service selection method for workflow reconfiguration based on interface operation matching. First, formal models of service workflow and interface operations of Web services are defined, and functional behavior comparisons of service selections are performed to determine the operation coverage set that will fulfill all activities that predefine the form of an abstract process. Second, reconfiguration patterns are introduced to describe different solution types for service patterns, including one-to-one, one-to-many, many-to-many, and many-to-one modes. Third, to consider the quality of service (QoS), the quality of service workflow (QoW) is proposed according to control structures and service interface computing, and the unified QoW formula is then provided to effectively rank each reconfiguration plan to provide a top-k solution recommendation. Fourth, related algorithms and a case study are discussed to show the service selection process during the workflow reconfiguration. To support the engineering implementation, a novel service workflow reconfiguration architecture is designed to provide guidance, which ranges from monitoring to recommendations for project implementation. Finally, experiments are conducted to demonstrate the effectiveness and efficiency of the proposed method.

Pattern-Reconfigurable, Flexible, Wideband, Directive, Electrically Small Near-Field Resonant Parasitic Antenna

A pattern-reconfigurable, flexible, wideband, directive, electrically small near-field resonant parasitic (NFRP) antenna is presented. The antenna consists of a pair of Egyptian axe dipole NFRP elements, together with a pair of shaped metallic strips that act as the driven element and are fed by a coaxial cable. These NFRP and driven elements are designed to achieve compactness. Two pairs of p-i-n diodes are integrated into the driven element to enable the pattern reconfigurability. The antenna has two switchable directive endfire states, each pointed in direct opposition to the other. Examples of the evolution of the antenna are used to illustrate its operating principles. A prototype of the optimized design operating in a frequency range centered at 1.8 GHz was fabricated and measured. The simulation and experimental results are in good agreement. The antenna exhibits a wide ~13.1% impedance bandwidth and a ~4.42 dBi peak realized gain in both pattern-reconfigurable states while maintaining its electrically small size: $\textit {ka} \sim 0.94$ . The flexibility of this antenna is demonstrated under different bending conditions by mounting it on cylinders with several different radii, and the results confirm that its performance characteristics are maintained under all of them.

Core networks and their reconfiguration patterns across cognitive loads.

Different cognitively demanding tasks recruit globally distributed but functionally specific networks. However, the configuration of core networks and their reconfiguration patterns across cognitive loads remain unclear, as does whether these patterns are indicators for the performance of cognitive tasks. In this study, we analyzed functional magnetic resonance imaging data of a large cohort of 448 subjects, acquired with the brain at resting state and executing N-back working memory (WM) tasks. We discriminated core networks by functional interaction strength and connection flexibility. Results demonstrated that the frontoparietal network (FPN) and default mode network (DMN) were core networks, but each exhibited different patterns across cognitive loads. The FPN and DMN both showed strengthened internal connections at the low demand state (0-back) compared with the resting state (control level); whereas, from the low (0-back) to high demand state (2-back), some connections to the FPN weakened and were rewired to the DMN (whose connections all remained strong). Of note, more intensive reconfiguration of both the whole brain and core networks (but no other networks) across load levels indicated relatively poor cognitive performance. Collectively these findings indicate that the FPN and DMN have distinct roles and reconfiguration patterns across cognitively demanding loads. This study advances our understanding of the core networks and their reconfiguration patterns across cognitive loads and provides a new feature to evaluate and predict cognitive capability (e.g., WM performance) based on brain networks.

Analysis and design of sea-water monopole Yagi-Uda antenna with pattern reconfigurability

In this article, a theoretical study of sea-water monopole Yagi-Uda antenna is presented. Unlike the conventional metal one, sea-water monopole is here treated as imperfect conductor. Based on this precondition, a methodology for analyzing sea-water monopole Yagi-Uda antenna is proposed by employing the 3-term theory and voltage-current relation. As such, both its input impedance and radiation pattern can be theoretically predicted. Commercial software packages ANSYS HFSS and CST Microwave Studio are used to verify the proposed methodology. Finally, a prototype is designed, fabricated, and tested. Due to the liquidity of sea water, the parasitic element can work as a director or reflector by altering its height to achieve pattern reconfigurability. Measured results show reasonably good agreement with the simulated and theoretical ones.

A Frequency- and Pattern-Reconfigurable Two-Element Array Antenna

A frequency- and pattern-reconfigurable two-element array antenna based on a stub-loaded configuration is presented. The frequency-tuning mechanism is implemented using varactor diodes loaded with open stubs. Two independent bias voltages allow to independently add pattern reconfigurability to the array. This is achieved by slightly detuning the resonances of the two patches, thus introducing a beam-steering relative phase difference between them. The design is optimized for a relative frequency tuning range of $\text{10}\%$ extending from 2.15 to 2.38 GHz, within which it presents a continuously beam-steerable radiation pattern covering scanning angles from $-\text{23}^{\circ }$ to $+ \text{23}^{\circ }$ across broadside. An antenna prototype is experimentally characterized, which validates the proposed concept.

A Patch-Slot Antenna Array With Compound Reconfiguration

This letter presents the design of a novel compound reconfigurable antenna array for WiMAX and WLAN application. The proposed array consists of a unit-cell antenna composed of a truncated circular radiator, C-shaped parasitic elements, and perturbed rhombic slot element. A compound reconfigurable unit-cell antenna element loaded with p-i-n diodes is investigated, and using the inference made, a 1 × 2 array is designed to increase the gain and efficiency of the dynamic antenna. In the first case, slot antenna alone gets excited with the feedlines of 0° and 90° phase difference to achieve pattern and polarization reconfiguration for WiMAX applications. In the other case, the patch is excited at the WLAN band and, with the help of parasitic elements, pattern tilting at 0° and ±30° is obtained. The proposed antenna array is fabricated, and the simulation results are verified using experimental measurements.

Circularly Polarized Antenna With Reconfigurable Broadside and Conical Beams Facilitated by a Mode Switchable Feed Network

A pattern-reconfigurable slot-augmented patch antenna is reported that radiates circularly polarized (CP) fields and is switchable between a broadside and a conical radiating mode. Two novel design strategies were adopted to realize these advantageous performance characteristics. First, a mode switchable feed network which includes a set of eight L-probes was developed that facilitates the proper excitation of either the patch’s TM11 or TM21 mode and yields symmetric radiation patterns. Second, their operating bands were made to overlap by augmenting this patch with an annular slot. Consequently, the radiation pattern is easily switched between the broadside and the conical modes within the overlapping operational bandwidths. A prototype was fabricated and tested. The measured results are in good agreement with their simulated values, verifying the design concepts. The measured operating bandwidth, 7.8% from 2.45 to 2.65 GHz, was determined from the overlap of the impedance and axial ratio bandwidths for both modes. The measured realized gain values are stable for both radiating states within this operational bandwidth, the broadside (conical) peak value being 8.5 dBic (5.8 dBic). The CP pattern reconfigurability of this antenna with its favorable performance characteristics makes it an ideal candidate for many RFID and satellite communication applications.

Dual Feed Pattern Reconfigurable Antenna for Wireless Applications

In this paper, a novel dual band dual feed multiple input multiple output reconfigurable antenna is designed. On-plane printing methodology is focused in designing the antenna. To implement the design, a circular Defected Ground Structure (DGS) with concentric split ring is employed beneath the signal plane and the reconfiguration is attained without using any switching elements. The signal plane comprises of octagonal ring pattern with orthogonal dual feed arrangement. The antenna prototype has the dimension of 0.66ź × 0.66ź, where the octagonal ring is of 0.34ź. An impedance of 50 Ω is maintained in designing the prototype. The dual band has been achieved by the periodic property of split ring employed within the circular DGS in the ground plane. Alternate shorting of ports has been performed to attain the reconfiguration. The prototype is designed to be utilized in public safety and aeronautical radio navigation under US standards at 0.816 and 1.072 GHz with reflection coefficients of ź 17 and ź 21 dB respectively. The patterns have been reconfigured by terminating one of the ports with 50 ź impedance termination. This resulted in change of beam directions, attaining pattern reconfiguration.

Design of Frequency- and Pattern-Reconfigurable Wideband Slot Antenna

A wideband slot antenna with frequency- and pattern-reconfigurable characteristics for TD-LTE (3.4–3.8 GHz) and C-band (3.7–4.2 GHz) applications is proposed. The antenna consists of two symmetric slots that are fed by a fork-shaped microstrip line. Two PIN diodes are loaded in the slots to produce two different frequency bands. Meanwhile, two additional PIN diodes are inserted in the feed line to achieve the pattern reconfigurability. The wideband operation is realized by using the symmetric slots and fork-shaped feed line. Simulated and measured results show that the antenna provides 25° and 20° beam-steering in 3.4–3.8 and 3.7–4.2 GHz bands, respectively. Also, an impedance bandwidth of at least 12.8% is obtained in the operating bands.

Broadband Pattern Diversity Patch Antenna With Switchable Feeding Network

A single-feed wideband pattern diversity antenna is presented in this paper. The pattern reconfigurability is realized by a p-i-n-diodes-intergrated switchable feeding network with the ability of providing 0° in-phase or 180° out-of-phase antenna excitation. The radiating patch is excited by the feeding network through a pair of symmetric stepped probes. When the two stepped probes are with in-phase excitation, a conical mode can be generated on the patch. On the other hand, the antenna can operate at a broadside mode if the excitation is out-of-phase. A meticulous prototype is developed, manufactured, and measured. The measured impedance bandwidths of the 10-dB return loss are 60.7% from 1.95 to 3.65 GHz for the broadside mode and 72.7% from 1.65 to 3.65 GHz for the conical mode. Meanwhile, measured peak gains of up to 10.2 and 7.7 dBi and measured radiation efficiencies of higher than 80% and 76% are obtained for the broadside mode and conical mode, respectively.

Pattern-Reconfigurable Unidirectional Dipole Antenna Array Fed by SIW Coupler for Millimeter Wave Application

A directional two-element mm-wave dipole antenna array with reconfigurable patterns is presented in this paper. An substrate integrated waveguide (SIW) 90° coupler is used to realize reconfigurable patterns of the antenna array. The two dipole elements are parallel in space, and there is a distance of $\lambda _{0}$ /4 ( $\lambda _{0}$ is the wavelength of the free space) between them. When the two inputs of the 90° coupler are excited, respectively, two completely opposite radiation patterns are able to be achieved. In order to further enhance the directivity of the proposed antenna, two groups of novel zero-index metamaterials and three metallic strips are introduced. As a consequence, a 0.7–1.2 dBi gain enhancement and reduced back lobe are obtained within the working frequencies. The measured amplitudes of S11 and S22 are below −10 dB from 45.5 to 49.5 GHz, and the measured gain is all great than 5 dBi within this band.

A Pattern Reconfigurable MIMO Antenna Design Using Characteristic Modes

A novel pattern-reconfigurable two-port multiple-input multiple-output (MIMO) antenna system at Wi-Fi band has been designed by resorting to characteristic modes analysis. The design method of the proposed MIMO antenna array is based on the selective excitation of three orthogonal characteristic modes. The selective excitation is achieved by integrating two pairs of capacitive coupling elements (CCEs) on the same plane with the ground. Two feeding networks related to two ports have been designed for achieving a good impedance matching and providing the feeding to the CCEs. By switching the p-i-n diodes in each feeding network, the selective excitation mode of the two ports can be varied, thus leading to the reconfigurable patterns. Three operating states can be obtained for the proposed antenna design. Simulation results demonstrate that the envelope correlation coefficients of the proposed MIMO antenna array are far less than 0.5 due to the orthogonality of radiation patterns between the characteristic modes in each of the three states. Measured S-parameters and the radiation patterns of a realized prototype are in good agreement with simulation ones confirming the reliability of the design method.

In Situ Electrical Properties’ Investigation and Nanofabrication of Ag/Sb2Te3 Assembled Multilayers’ Film

AbstractNanopatterned fabrication and electrical properties of Ag/Sb2Te3 layer‐by‐layer assembled films are systematically investigated by a conductive atomic force microscope. Multilayers’ film composed by alternating Ag and Sb2Te3 with respective thicknesses of 5 and 10 nm shows a bipolar resistive switching behavior contributed by the silver conductive filaments. Designed cross‐plane nanofilament arrays with reconfigurable patterns are fabricated, which show a potential application in memristor and nanofabrication. Multilayers with the same thickness of Ag but increased thickness of Sb2Te3 (up to 20 nm) present a Fowler–Nordheim tunneling‐dominated current and show in‐plane snowflake silver dendrite on the surface. Further studies on the silver dendrite may bring potential applications in extensive fields such as multifunctional data storage and neuromorphic. By controlling the type (Sb2Te3, Bi2Te3, etc.) and thickness of solid electrolyte materials, electronic devices with specific functions and applications can be designed.

A novel reconfigurable radiating plasma antenna array based on Yagi antenna technology

An electronically controlled plasma reflector antenna array is presented in term of Yagi antenna technology and plasma theory in this paper. The array comprised of a plasma symmetrical dipole in the center and 6 plasma column antennas uniformly around the dipole. When only the active plasma dipole and one of passive columns are energized, they perform like conductive metals capable to radiate radio signal like a two-element plasma Yagi antenna. Pattern reconfigurability of the antenna array can be achieved by sequentially exciting one of 6 plasma columns, and the plasma antenna array also produces better gain through increasing the number of plasma reflectors. Due to the adoption of equal amplitude and phase feeding technology, it greatly reduces the technical difficulty of the implementation of pattern reconfigurability. On the other hand, if all of plasma columns are off, there is only minor reflection from dielectric tubes, and hence, the plasma antenna array has stealth performance.

Parasitic Layer-Based Radiation Pattern Reconfigurable Antenna for 5G Communications

The design, prototyping, and characterization of a radiation pattern reconfigurable antenna (RA) targeting 5G communications are presented. The RA is based on a reconfigurable parasitic layer technique in which a driven dipole antenna is located along the central axis of a 3-D parasitic layer structure enclosing it. The reconfigurable parasitic structure is similar to a hexagonal prism, where the top/bottom bases are formed by a hexagonal domed structure. The surfaces of the parasitic structure house electrically small metallic pixels with various geometries. The adjacent pixels are connected by PIN diode switches to change the geometry of the parasitic surface, thus providing reconfigurability in the radiation pattern. This RA is designed to operate over a 4.8–5.2 GHz frequency band, producing various radiation patterns with a beam-steering capability in both the azimuth ( $0 {^{\circ }} ) and elevation planes ( $-18 {^{\circ }} ). Small-cell access points equipped with RAs are used to investigate the system level performances for 5G heterogeneous networks. The results show that using distributed mode optimization, RA equipped small-cell systems could provide up to 29% capacity gains and 13% coverage improvements as compared to legacy omnidirectional antenna equipped systems.

Laser-induced erasable patterns in a N* liquid crystal on an iron doped lithium niobate surface.

A chiral nematic (N*) liquid crystal (LC) was hybridized with a z-cut iron doped lithium niobate (Fe:LN) substrate and exposed with a focused continuous wave diode laser beam. The N* LC layer was confined with a cover glass to provide a homogeneous LC layer thickness. Two distinct kinds of test cells were investigated, one with an uncoated glass covering slip and one with an indium tin oxide (ITO) coated cover glass. Photo generated electric fields (generated in the Fe:LN) resulted in a localized defect formation and textural transitions in the N* LC. Due to field confinement, the field induced responses were more localized in samples with ITO coated cover glasses. By scanning the laser beam on programmed trajectories, formation of persistent patterns could be achieved in the N* LC layer. Polarized optical microscopy of the exposed samples revealed that these patterns consisted of adjacent circular Frank-Pryce defects. Exposure with a slightly defocused laser beam could be applied selectively to erase these patterns. Thus, a promising method is reported to generate reconfigurable patterns, photonic motives, and touch sensitive devices in a hybridized N* LC with micron accuracy.

A Reconfigurable MIMO Antenna System for Wireless Communications

A reconfigurable antenna system is proposed to improve data throughput limitations in multiple input multiple output wireless communication systems in this investigation. The 4×4 MIMO antenna is designed to operate in the 2.4 and 2.6 GHz for Wireless Local Area Network (WLAN) and Long Term Evolution (LTE) applications. The system's radiation pattern re-configurability is realized by using the microcontroller-driven PIN diode switching concept. Simulations and measurements exhibited good agreements for the single, 2×2 MIMO and 4×4 MIMO configurations. The antenna is operational between 2.387 to 2.628 GHz, while the simulated and measured reflection coefficients are at least −24.3 dB. All configurations produced a narrow beam forward radiation, while the envelope correlation coefficient (ECC) and diversity gain for the two MIMO configurations are below 0.5 and at least 9 dBi, respectively.

Frequency-Agile Beam-Switchable Antenna

A novel antenna with both frequency and pattern reconfigurability is presented. The reconfigurability is achieved by integrating an active frequency selective surface (AFSS) with feed antenna. The smart FSS comprises a printed slot array loaded by varactors. A novel dc biasing arrangement is proposed to feed the slots vertically so that the unwanted effects caused by bias lines are minimized. A monopole antenna is designed to illuminate the AFSS. The resulting structure can operate in a frequency tuning range of 30%. By reconfiguring the different sections of active FSS cylinder into a transparent or reflector mode, the omnidirectional pattern of the source antenna can be converted to a directive beam. As an illustration, half of the AFSS cylinder is successively biased, enabling the beam switching to cover the entire horizontal plane over a range of frequencies. An antenna prototype was fabricated and measured. Experimental results demonstrate the capability of providing useful gain levels and good impedance matching from 1.7 to 2.3 GHz. The antenna offers a low-cost, low-power solution for wireless systems that require frequency and beam reconfigurable antennas. The proposed design consumes about 1000 times less dc power than the equivalent narrowband beam-switching antenna design using p-i-n diode-loaded AFSS.

PATTERN-RECONFIGURABLE ANTENNA FOR 5.5-GHZ WIMAX APPLICATIONS

Pattern reconfigurable antenna, which is based on multi-switchable radiators with rectangular reflectors, is presented. The antenna utilized the self-similarity double ring configuration property in the form of rectangular and a Wilkinson power divider feeder, to exhibit wideband and radiation pattern reconfiguration characteristics. The pattern reconfiguration is achieved by feeding these self-similarity double rings of antenna in two directions. A few switches and power divider is used in order to change the feeding direction. The antenna is capable of steering the beam in the four directions 25˚, 52˚, 155˚ and 158˚ in the azimuth plane and, four directions 20˚, 10˚, 5˚, and 51˚ in the elevation plane, depending on the state of switches loaded on the rectangular rings. Initial results were obtained by using short and open circuits to represent ON and OFF for switches respectively. The proposed reconfigurable antenna has the advantage of miniaturization, simple reconfigurable, low profile, light weight, and easy fabrication. For verification of simulation results, the proposed antenna is fabricated and the prototype is measured using R&S ZVL 13 Vector Network Analyzer. The results show a good agreement between simulated and measured results.