Antenna Alignment Research Articles

Learning and Uncertainty-Exploited Directional Antenna Control for Robust Long-Distance and Broad-Band Aerial Communication

Aerial communication using directional antennas (ACDA) is a promising solution to enable long-distance and broad-band unmanned aerial vehicle (UAV)-to-UAV networking. The automatic alignment of directional antennas allows the transmission energy to focus in certain direction and significantly extends the communication range and rejects interference. Robust automatic alignment of directional antennas is not easy to achieve, considering practical issues such as the limited on-board sensing devices due to the physical constraints of UAV payload and power supplies, uncertain and varying UAV movement patterns, and unstable GPS and unknown communication environments. In this paper, we develop reinforcement learning (RL)-based online antenna control solutions for the ACDA system to conquer these challenges. The control solution adopts an uncertain UAV mobility modeling and intention estimation framework to capture and predict the uncertain intentions of UAV maneuvers and hence permit robust tracking. To account for an unstable GPS environment, the control solution features a learning of communication channel models to provide additional measurement signals in GPS-denied settings. A novel stochastic optimal control solution for nonlinear random switching dynamics is developed that integrates RL, an effective uncertainty evaluation method called multivariate probabilistic collocation method (MPCM), and unscented Kalman Filter (UKF). Simulation studies are conducted to illustrate and validate the proposed solutions.

Design and implementation of aerial communication using directional antennas: learning control in unknown communication environments

To support an increasing number of commercial multi-unmanned aerial vehicle (UAV) applications, robust UAV-to-UAV communication is critical. A promising solution is aerial communication using directional antennas (ACDA), with features like long communication distance, low power consumption, broad bandwidth, and interference rejection. Nevertheless, ACDA requires the automatic alignment of directional antennas, which is not easy to achieve considering the imperfect communication environment unknown in advance and the limited sensing devices onboard due to the constrained payloads and power sources. In this study, the authors design and implement a new ACDA system, including the platform, communication, computing, control, middleware, and interface components. Practical implementation issues for the emergency response application are also considered. The ACDA system features a communication and control co-design, where the communication quality indicator, received signal strength indicator, serves as the goal function for antenna alignment. The solution also features a reinforcement learning-based directional antenna control algorithm that learns the unknown communication environment models. The performance of the ACDA system is verified using simulation studies, field tests, and disaster drills.

Antenna alignment by using computer vision technology

AbstractAn automatic alignment approach is proposed for tracking unmanned aerial vehicle (UAV) antennas by using computer vision technology. In this approach, UAV carries a low‐gain omnidirectional antenna and a ground station uses high gain directional antenna which can be driven by a pan‐tilt to point to UAV's antenna. A camera is bound together with the antenna and a computer is employed to recognize the video and control motion of the pan‐tilt, so as to move the image of UAV's antenna toward the center of the whole picture. If the distance between center of UAV image and center of the picture is kept within a few pixels, then the antennas are aligned. Performance analysis and experiment results are given, showing that the proposed antenna autoalignment approach can achieve accurate alignment of the antennas with an angle error of less than 1°.

Alignment-and-metrological facility for fine adjustment of antenna linear and angular position during spacecraft assembly

The paper discusses issues involved in fine adjustment of the linear and angular position of antenna system reflectors on a spacecraft (SC) during its assembly using an alignment-and-metrology facility that has been developed, which consists of a 6-DOF pointing device and a laser coordinate measurement tracker. Achieving the specified linear and angular positions of antenna system elements in the SC datum reference frame, reducing human effort and time needed to perform this processing operation is an important task when building a spacecraft. To address this problem, a procedure was developed and tried out during an actual SC assembly consisting in the joint use of the 6-DOF pointing device Hexapod PM-mkm-P and the high-precision laser tracker Leica AT 403 for measuring the coordinates. An algorithm was developed for hardware/software interfacing between elements of the alignment-and-metrology facility, which provides iterative linear and angular positioning of the antenna reflectors in a closed loop with a feedback. The paper discusses sources of errors and the way to minimize their effect on the operation of various types of pointing using continuous monitoring by means of an external measuring system. The developed alignment-and-metrology facility provided high-precision spatial positioning of antenna elements in the SC coordinate system, which made it possible to rule out any errors by operator/installation worker during alignment and significantly reduce the time needed to perform the said operation. Key words: spacecraft, antenna alignment, 6-DOF hexapod-type platform with parallel kinematics, Gough-Stewart platform, laser coordinate measuring system.

Wireless Power Transfer Antenna Alignment Using Intermodulation for Two-Tone Powered Implantable Medical Devices

Wireless power transfer (WPT) to the implantable medical devices (IMDs) often suffers from antenna radiation direction and polarization misalignments, which degrades the wireless power link efficiency. Although increasing the incident power density is able to solve the power hunger of IMDs, it poses safety issues to the human tissue. In this paper, an antenna alignment method using intermodulation is proposed to address WPT antenna misalignment in a safe way. Two-tone (2T) waveform excitation is employed to enhance the rectification as well as to generate intermodulation. The intermodulation power is fed back via a magnetic resonant coupling link. Due to the monotonic relation between the intermodulation power and the degree of antenna misalignments, the receiving antenna (in body) can be aligned with the transmitting one (out body). Such a scheme has the advantages of less harm to human tissue and less interference between the 2T waveform excitation and the magnetic resonant coupling link. The whole system is theoretically analyzed and experimentally validated.

MmWave Backhaul Testbed Configurability Using Software-Defined Networking

Future mobile data traffic predictions expect a significant increase in user data traffic, requiring new forms of mobile network infrastructures. Fifth generation (5G) communication standards propose the densification of small cell access base stations (BSs) in order to provide multigigabit and low latency connectivity. This densification requires a high capacity backhaul network. Using optical links to connect all the small cells is economically not feasible for large scale radio access networks where multiple BSs are deployed. A wireless backhaul formed by a mesh of millimeter-wave (mmWave) links is an attractive mobile backhaul solution, as flexible wireless (multihop) paths can be formed to interconnect all the access BSs. Moreover, a wireless backhaul allows the dynamic reconfiguration of the backhaul topology to match varying traffic demands or adaptively power on/off small cells for green backhaul operation. However, conducting and precisely controlling reconfiguration experiments over real mmWave multihop networks is a challenging task. In this paper, we develop a Software-Defined Networking (SDN) based approach to enable such a dynamic backhaul reconfiguration and use real-world mmWave equipment to setup a SDN-enabled mmWave testbed to conduct various reconfiguration experiments. In our approach, the SDN control plane is not only responsible for configuring the forwarding plane but also for the link configuration, antenna alignment, and adaptive mesh node power on/off operations. We implement the SDN-based reconfiguration operations in a testbed with four nodes, each equipped with multiple mmWave interfaces that can be mechanically steered to connect to different neighbors. We evaluate the impact of various reconfiguration operations on existing user traffic using a set of extensive testbed measurements. Moreover, we measure the impact of the channel assignment on existing traffic, showing that a setup with an optimal channel assignment between the mesh links can result in a 44% throughput increase, when compared to a suboptimal configuration.

Dual‐mode charge pump with second‐harmonic readout for antenna alignment in wireless power transfer system

A charge pump is presented by integrating two identical voltage doublers and a modified rat-race coupler to enable its dual-mode operations: radio-frequency (RF)-to-direct current (dc) power conversion and second-harmonic readout. Due to the property of the modified rat-race coupler, it is able to differentially divide incident RF signals for successive voltage doublers' high-efficiency rectification, and couple second harmonics for readout in two highly isolated channels. Output dc voltages are combined in parallel on a single load resistance for more practicality. Experimental validations are demonstrated by both simulation and measurement with a maximum RF-to-dc power conversion efficiency of 71.3% and -14.2 dBm second-harmonic generation with an incident signal power of 19 dBm. This dual-mode charge pump brings a prospect for antenna alignment in the wireless power transfer system by further exploiting second harmonics.

Exploiting Third Harmonic of Differential Charge Pump for Wireless Power Transfer Antenna Alignment

Wireless power transfer (WPT) always suffers from the antenna radiation direction and polarization misalignments between the base station and the WPT terminal. In this letter, the third harmonic of a differential charge pump is exploited for antenna alignment with only one pair of antennas. Due to the intrinsic nonlinearity of diodes, the third harmonic can be generated and reflected by the differential charge pump. A ring coupler is employed to distribute the received fundamental frequency power for rectification by the differential charge pump and couple the third-harmonic generation back to its input port. Such third-harmonic power is feedback by a dual-band antenna operating at the third-harmonic frequency. In consequence, the WPT antennas can be aligned by obtaining the maximum third-harmonic feedback at the base station. The whole system is theoretically analyzed and experimentally validated.

Research on Antennas Alignment of Dynamic Point-to-Point Communication

In the dynamic point-to-point communication, to track and aim at antenna fast and accurately is the guarantee of high quality communication signal. In order to solve the problem of antenna alignment, we used the least square method (LSM) to fit the optimal level signal value (LSV) point which is based on coordinate coarse tracking alignment and matrix scanning strategy to find the LSV in this paper. Antenna is driven by two-dimensional turntable (azimuth and elevation angle (AE)): the two-dimensional turntable is decomposed into two independent one-dimensional turntables, and the LSV in AE direction are obtained by scanning, respectively. The optimal LSV point of two-dimensional turntable can be find by combing optimal LSV point of two independent one-dimensional turntables. The method has the advantages of high precision and easy implementation and can meet the requirement of fast and accurately alignment in dynamic point-to-point communication antenna engineering.

Wireless Power Transfer Antenna Alignment Using Third Harmonic

The efficiency of wireless power transfer (WPT) always suffers from misalignment between transmitting and receiving directional antennas. In this letter, a maximum radiation direction alignment method is proposed for WPT using the unexploited third harmonic generated from rectifiers. The widely used second harmonic is untouched, retaining the possibility of its further recycling. A hybrid coupler is used for the received power distributing and third-harmonic coupling simultaneously. Due to the nonlinearity of diodes, the third harmonic is generated during the rectification and reflected back by the rectifier filter. Its power is completely returned to the base station by the same hybrid and another antenna pair working at the third-harmonic frequency. Maximum power transfer is thus realized when both transmitting and receiving antennas are aligned. The proposed method is validated by Advanced Design System simulation and measurement.

Enhancements in mm‐wave antenna measurements: automatic alignment and achievable accuracy

Due to various error sources, accurate integrated antenna measurements can be difficult to achieve. This study analyses the accuracy of a measurement set-up for radiation pattern (RP), directivity and gain measurements. The main sources of uncertainty are pointed out and the overall achievable accuracy is determined. The expanded uncertainty budgets for RP, directivity and gain measurements are 0.2, 0.2 and 1.7 dB, respectively. Furthermore, the phase centre of the antenna under test (AUT) is calculated for a more accurate and faster antenna alignment. The standard deviation of the calculated phase centre position is 50 μm on each axis.

LOCALI: Calibration-Free Systematic Localization Approach for Indoor Positioning.

Recent advancements in indoor positioning systems are based on infrastructure-free solutions, aimed at improving the location accuracy in complex indoor environments without the use of specialized resources. A popular infrastructure-free solution for indoor positioning is a calibration-based positioning, commonly known as fingerprinting. Fingerprinting solutions require extensive and error-free surveys of environments to build radio-map databases, which play a key role in position estimation. Fingerprinting also requires random updates of the database, when there are significant changes in the environment or a decrease in the accuracy. The calibration of the fingerprinting database is a time-consuming and laborious effort that prevents the extensive adoption of this technique. In this paper, we present a systematic LOCALIzation approach, “LOCALI”, for indoor positioning, which does not require a calibration database and extensive updates. The LOCALI exploits the floor plan/wall map of the environment to estimate the target position by generating radio maps by integrating path-losses over certain trajectories in complex indoor environments, where triangulation using time information or the received signal strength level is highly erroneous due to the fading effects caused by multi-path propagation or absorption by environmental elements or varying antenna alignment. Experimental results demonstrate that by using the map information and environmental parameters, a significant level of accuracy in indoor positioning can be achieved. Moreover, this process requires considerably lesser effort compared to the calibration-based techniques.

Terahertz transmission control using polarization-independent metamaterials.

We present terahertz (THz) transmission control by several uniquely designed patterns of nano-slot antenna array. Collinearly aligned slot antenna arrays have been usually applied to THz filters with frequency band tunability by their geometry. Normally the amplitude in transmission (reflection) in the collinear alignment case can be varied via rotating the azimuthal angle with a sinusoidal trend, which can limit their utilization and performance only at fixed angle between the alignment of the resonant antennas and incident beam polarization. To pursue a variety of metamaterial uses, here, we present polarization-independent THz filters using variously aligned antenna array (asterisk, chlorophyll, and honeycomb patterns) in such counter-intuitive aspects. Besides, unprecedented multi resonance behaviors were observed in chlorophyll and honeycomb patterns, which can be explained with interferences by adjacent structures. The measured spectra were analyzed by harmonic oscillator model with simplified coupling between slots and their adjacent.

Performance analysis for W‐band antenna alignment using accurate mechanical beam steering

ABSTRACTThis article presents a study of antenna alignment impact on bit error rate for a wireless link between two directive W‐band horn antennas where one of them is mechanically steered by a Stewart platform. Such a technique is applied to find the optimal alignment between transmitter and receiver with an accuracy of 1° both in azimuth and elevation angles. The maximum degree of misalignment which can be tolerated is also reported for different values of optical power in the generation of W‐band signals by photonic up‐conversion. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:1125–1128, 2017

Analysis and Improvement of the Effectiveness of General Quantities of the Radio Links with Short Vibrator Antennas for Shortwave and Ultra-Shortwave Bands

Влияние приемопередающих антенн остается основным из факторов, определяющих эффективность радиолинии. В статье выполнен расчет параметров полуволновых и укороченных симметричных вибраторных антенн. Рассмотрен расчет параметров укороченных штыревых антенн и факторы повышения их эффективности. Предложены способы повышения эффективности укороченных антенн: использование системы противовесов для уменьшения сопротивления потерь; применение согласующих индуктивностей, утолщение антенны и добавление концевой емкости на верхний конец штыря для уменьшения реактивной составляющей входного сопротивления антенны. Вместе с этим на практике особенно важное значение следует придавать вопросам юстировки и настройки укороченных антенн и их согласующих устройств. Приведен пример моделирования укороченной антенны в программе ММАNА.

Electromagnetic Simulation and Alignment of Dual-Polarized Array Antennas in Multi-Mission Phased Array Radars

Electromagnetic (EM) simulation of dual-polarized antennas is necessary for precise initial alignments, calibration and performance predictions of multi-function phased array radar systems. To achieve the required flexibility and scalability, a novel Finite-Difference Time-Domain (FDTD) solution is developed for rectangular, cylindrical and non-orthogonal coordinate systems to simulate various types of array antenna manifolds. Scalable array pattern predictions and beam generations are obtained by combining the FDTD simulation solutions with the Near-Field (NF) chamber measurements. The effectiveness and accuracy of this approach are validated by comparing different simulations and comparing simulations with measurements.

Elevator Safety Monitoring and Early Warning System Based on Directional antenna transmission technology

In order to solve problems of the absence of security protection and the lack of early warning mechanism in the current elevator operation process, elevator safety monitoring and early warning system based on directional antenna transmission technology was proposed. The system includes sensor module circuit, microcontroller module circuit, display module, directional antenna transmission module, remote server and data monitoring system. Design ideas of hardware development, remote server and data monitoring system are introduced. Two version monitoring software are written, one for PC monitor, the other one for mobile phone monitoring. In order to improve data transmission distance, transmission rate and transmission quality, automatic antenna alignment system is designed, which combines the advantages of directional antennas and omnidirectional antennas transmission technique. To overcome problems such as instability of the alignment process, delay and other factors, DMC（ Dynamic Matrix Control ） algorithm should be used in the system and optimal control of the antenna angular alignment will be achieved. The system can continuously transmit real-time elevator’s working status information and environmental information, and it also send commands to notify elevator company managers once an abnormal conditions occur in the elevator, so that people can take urgent measures and maintenance measures. This system can be applied to real-time warning of all-types elevators.

衛星姿勢/アンテナ協調制御及びアンテナアライメント誤差推定に関するALOS-2軌道上評価結果

衛星姿勢/アンテナ協調制御及びアンテナアライメント誤差推定に関するALOS-2軌道上評価結果

Generalized Spatial Modulation Based Reduced-RF-Chain Millimeter-Wave Communications

A generalized spatial modulation (GSM)-based millimeter-wave communications system is proposed. The GSM transmitter is characterized by a lower number of radio frequency (RF) chains than the number of transmit antennas; hence, it is capable of reducing both the transmitter cost and the energy consumption. The antenna array alignment is optimized so as to maximize the rank of the channel matrix encountered. Furthermore, we employ an array of analog beamformers, which allows us to benefit both from the beamforming gain and from the GSM scheme's high rate. It is demonstrated that the constrained capacity of the GSM transmitter equipped with as few as two RF chains is capable of approaching the performance of the full-RF spatial multiplexing having eight RF chains.

Position-Aided mm-Wave Beam Training Under NLOS Conditions

Ray tracing simulation results indicate that a high-resolution database is not needed to exploit user position knowledge in the 28-GHz band, even in the case of inexact information. A proposed antenna alignment algorithm (using maximum position errors and database resolutions of 10 and 4 m, respectively) that takes advantage of the propagation characteristics knowledge of database points located around the reported location is applied. The results show that the distance between the points can be increased up to 2 m with no considerable negative impact on performance. Simulations also indicate that this outcome is sustained when the maximum power level received at the user equipment varies. The algorithm provides the benefit of a higher initial power delivery and fewer steps, as long as the exact geographical position of the user is within the circular area containing the considered database points. The performance is similar to or better than that of a modified classical hierarchical procedure.