Ultra-wideband Modulation Research Articles

Onboard cooperative relative positioning system for Micro-UAV swarm based on UWB/Vision/INS fusion through distributed graph optimization

In recent years, the swarm of micro Unmanned Aerial Vehicles (micro-UAVs) is becoming a research hotspot. As the basis of swarm autonomous flight, traditional relative positioning methods typically rely on external base stations or onboard sensors of high power consumption, the vast majority of which are not feasible on resource-constrained micro-UAVs flying in a complex environment. This article proposes a lightweight relative positioning system implemented on a micro-UAV platform weighing 150 g. We have developed a distributed graph optimization (DGO) scheme fusing the results of the onboard Ultra-Wideband (UWB) module, camera, and inertial sensors. A Delay Extended Kalman Filter (DEKF) is utilized to mitigate communication delays and enhance accuracy. This scheme enables micro-UAVs to collaboratively compute the relative position graph in real-time. Through real-world experiments, our system has achieved a relative positioning accuracy of 0.167 m, exhibiting significant potential for future swarm applications.

Push the Limit of Highly Accurate Ranging on Commercial UWB Devices

Ranging plays a crucial role in many wireless sensing applications. Among the wireless techniques employed for ranging, Ultra-Wideband (UWB) has received much attention due to its excellent performance and widespread integration into consumer-level electronics. However, the ranging accuracy of the current UWB systems is limited to the centimeter level due to bandwidth limitation, hindering their use for applications that require a very high resolution. This paper proposes a novel system that achieves sub-millimeter-level ranging accuracy on commercial UWB devices for the first time. Our approach leverages the fine-grained phase information of commercial UWB devices. To eliminate the phase drift, we design a fine-grained phase recovery method by utilizing the bi-directional messages in UWB two-way ranging. We further present a dual-frequency switching method to resolve phase ambiguity. Building upon this, we design and implement the ranging system on commercial UWB modules. Extensive experiments demonstrate that our system achieves a median ranging error of just 0.77 mm, reducing the error by 96.54% compared to the state-of-the-art method. We also present three real-life applications to showcase the fine-grained sensing capabilities of our system, including i) smart speaker control, ii) free-style user handwriting, and iii) 3D tracking for virtual-reality (VR) controllers.

GPS-Free Wireless Precise Positioning System for Automatic Flying and Landing Application of Shipborne Unmanned Aerial Vehicle.

This research is dedicated to developing an automatic landing system for shipborne unmanned aerial vehicles (UAVs) based on wireless precise positioning technology. The application scenario is practical for specific challenging and complex environmental conditions, such as the Global Positioning System (GPS) being disabled during wartime. The primary objective is to establish a precise and real-time dynamic wireless positioning system, ensuring that the UAV can autonomously land on the shipborne platform without relying on GPS. This work addresses several key aspects, including the implementation of an ultra-wideband (UWB) circuit module with a specific antenna design and RF front-end chip to enhance wireless signal reception. These modules play a crucial role in achieving accurate positioning, mitigating the limitations caused by GPS inaccuracy, thereby enhancing the overall performance and reception range of the system. Additionally, the study develops a wireless positioning algorithm to validate the effectiveness of automatic landing on the shipborne platform. The platform's wave vibration is considered to provide a realistic landing system for shipborne UAVs. The UWB modules are practically installed on the shipborne platform, and the UAV and the autonomous three-body vessel are tested simultaneously in the outdoor open water space to verify the functionality, precision, and adaptability of the proposed UAV landing system. Results demonstrate that the UAV can autonomously fly from 200 m, approach, and automatically land on the moving shipborne platform without relying on GPS.

Loss compensation of an ultra-wideband electro-optic modulator in heterogeneous silicon/erbium-doped lithium niobate.

Electro-optic modulators (EOMs) are indispensable elements for integrated photonic circuits. However, optical insertion losses limit the utilization of EOMs for scalable integration. Here, we propose a novel, to the best of our knowledge, EOM scheme on a heterogeneous platform of silicon- and erbium-doped lithium niobate (Si/Er:LN). In this design, electro-optic modulation and optical amplification are simultaneously employed in phase shifters of the EOM. The excellent electro-optic property of lithium niobate is maintained to achieve ultra-wideband modulation. Meanwhile, optical amplification is performed by adopting the stimulated transitions of erbium ions in the Er:LN, leading to effective optical loss compensation. Theoretical analysis shows that a bandwidth exceeding 170 GHz with a half-wave voltage of 3 V is successfully realized. Moreover, efficient propagation compensation of ∼4 dB is predicted at a wavelength of 1531 nm.

Design and Experimental Verification of Targeted and Variable Sprayer for the Potato

For potatoes, a crop with a specific plant spacing and a large row spacing, continuous spray has problems including low spraying accuracy and washability. In order to improve the utilisation of this crop, this manuscript designed a targeted and variable sprayer. To ensure that the spray function is achieved, the design and verification of the vehicle body and the targeting device of the sprayer were carried out. To guarantee that the automation and precision of spray are improved, the autonomous marching system based on the Ultra-wideband (UWB) module and the targeted and variable spray system based on the Open machine vision (Open MV) module, were built. The experiments showed that the sprayer could follow a preset route, correct its marching direction in time, and provide feedback on its position. The targeted and variable spray was influential on the surface and back of the leaf (about 66%) and more uniform than the general spray mode. Moreover, the sprayer’s targeted and variable spray mode reduced the amount of liquid applied by 37.9% compared to the continuous spray mode, significantly improving the liquid utilisation rate.

Fingerprinting-Based Indoor Positioning Using Data Fusion of Different Radiocommunication-Based Technologies

Wireless-radio-communication-based devices are used in more and more places with the spread of Industry 4.0. Localization plays a crucial part in many of these applications. In this paper, a novel radiocommunication-based indoor positioning method is proposed, which applies the fusion of fingerprints extracted with various technologies to improve the overall efficiency. The aim of the research is to apply the differences, which occur due to that different technologies behave differently in an indoor space. The proposed method was validated using training and test data collected in a laboratory. Four different technologies, namely WiFi received signal strength indication (RSSI), ultra-wideband (UWB) RSSI, UWB time of flight (TOF) and RSSI in 433 MHz frequency band and all of their possible combinations, were tested to examine the performance of the proposed method. Three widely used fingerprinting algorithms, the weighted k-nearest neighbor, the random forest, and the artificial neural network were implemented to evaluate their efficiency with the proposed method. The achieved results show that the accuracy of the localization can be improved by combining different technologies. The combination of the two low-cost technologies, i.e., the WiFi and the 433 MHz technology, resulted in an 11% improvement compared to the more accurate technology, i.e., the 433 MHz technology. Combining the UWB module with other technologies results in a less significant improvement since this sensor provides lower error rates, when used alone.

Angle of Arrival and Centimeter Distance Estimation on a Smart UWB Sensor Node

Accurate and low-power indoor localization is becoming more and more of a necessity to empower novel consumer and industrial applications. In this field, the most promising technology is based on Ultra-Wideband (UWB) modulation; however, current UWB positioning systems do not reach centimeter accuracy in general deployments due to multi-path and non-isotropic antennas, still necessitating several fixed anchors to estimate an object’s position in space. This paper presents an in-depth study and assessment of Angle of Arrival (AoA) UWB measurements using a compact, low-power solution integrating a novel commercial module with Phase Difference of Arrival (PDoA) estimation as integrated feature. Results demonstrate the possibility of reaching centimeter distance precision and 2.4° average angular accuracy in many operative conditions, e.g., in a 90° range around the center. Moreover, integrating the channel impulse response, the phase differential of arrival, and the point-to-point distance, an error correction model is discussed to compensate for reflections, multi-paths, and front-back ambiguity.

Research on AGV positioning method combined with IMU and UWB

Aiming at the problem that automated guided vehicle (AGV) is difficult to locate accurately due to the influence of environment and time drift when it works in the indoor intelligent storage system. In this paper, an extended kalman filtering (EKF) framework is designed. In order to make full use of the original ranging values of ultra wideband (UWB) and inertial measurement unit (IMU), the framework realizes the fusion positioning between UWB module and IMU module in a tight coupling manner, so as to ensure that the system can still work when the available base station signal is inaccurate. Firstly, for the problem that the traditional UWB positioning method is easily affected by the non-line of sight (NLOS) error indoors, the calculated positioning coordinate value is unstable. With the help of different NLOS probability distribution curves of different obstacles, the weighted least square method is applied to the UWB positioning method to determine the positioning coordinate value of UWB, which improves the sudden change of AGV positioning coordinate in the static environment. Then the data fusion algorithm is optimized, and the error value of IMU and UWB coordinate is taken as the observation value of EKF, which reduces the influence of cumulative error on IMU positioning results, provides the global optimal estimation of the system optimal state, and improves the fusion positioning accuracy. Finally, the measured data of UWB and IMU systems in indoor complex environment are simulated in MATLAB. The experimental results show that when NLOS signal seriously affects the positioning effect, the UWB and IMU combined positioning system can provide more reliable positioning results than the single IMU positioning system. It improves the positioning accuracy of AGV and provides a new idea for indoor positioning mode.

HRP UWB 채널임펄스응답의 측정 및 분석

Ultrawideband (UWB) wireless communication technology, which appeared 20 years ago, is becoming popular in various fields because the ability to measure the precise distance between UWB devices beyond wireless communication is being re-examined. The currently commercialized UWB technology is high-rate pulse repetition frequency (HRP) UWB technology, which uses high-speed UWB pulses of several tens of megahertz, and precise distance and direction measurements are made by using the characteristic changes of the channel impulse responses (CIRs). Therefore, to understand HRP UWB technology, it is necessary to understand the CIR characteristics first. However, because HRP UWB technology is commercially successful, the disclosure of the technology has been insufficient, so the understanding of the meaning of the CIR of HRP UWB technology is inadequate. Therefore, in this study, the CIR characteristics of HRP UWB integrated circuits are explained, and the CIR was measured in various environments using a DWM3000 HRP UWB module (Qorvo). These results are expected to be helpful in understanding UWB technology and applying it to various fields.

Drone Positioning System Using UWB Sensing and Out-of-Band Control

Research on drones becomes vigorous not only for single drone but also drone fleet, which operates multiple drones in a formation. To widen the applicability of drone fleet, high positioning accuracy and low latency are required. Most drone products or research use the Global Positioning System (GPS) for positioning, but the accuracy is insufficient for performing various drone missions in dense or indoor environments. In this paper, we present a novel Ultra-wideband (UWB) positioning system that uses an out-of-band network for control channel. Each UWB module serves as a remote sensor for detecting and positioning multiple drones. Unlike traditional anchor-tag based UWB ranging, all nodes in the proposed system have no distinction between the roles of anchor and tag by utilizing enhanced multidimensional scaling (MDS). We practically implemented our proposed system and evaluated the system with numerical experiments. Through the numerical analysis, we have found that the proposed system provides enough accuracy and low latency to be applied to the drone fleet.

Multi-clad optical fiber design for ultra-wideband modulation instability

Developments of electro-optic (EO) modulators do not have a satisfactory pace and bandwidth restrictions are still limited to several hundred GHz, thus, obtaining methods that enable using broadband optical channels are key factors in high-speed optical communications. In this paper, Modulation Instability (MI) as an approach in order to improve the performance of EO modulators, is investigated in the anomalous and zero-dispersion regimes of proposed optical fiber. In present conventional optical fibers, MI is observed over a few hundred gigahertz bandwidths at low pump power. In order to obtain ultra-wideband (a few Terahertz) bandwidths and maximum gain in the MI process at low pump power, a new structure for optical fiber is proposed. The genetic algorithm is utilized for performance optimization in optical fiber design. It is shown that the proposed optical fiber is able to support MI for a few Terahertz bands at low pump power (100 mW). Furthermore, in this analysis, it is demonstrated that higher-order dispersion terms have a strong impact on modulation instability. Finally, it is concluded that the geometrical and optical parameters of optical fiber are key factors to control modulation instability parameters (gain and bandwidth). The proposed optical fiber can be used as an optical booster in order to compensate frequency response of EO modulators, which is a considerable step forward in high-speed optical communication.

A Wirelessly Powered Reconfigurable FDD Radio With On-Chip Antennas for Multi-Site Neural Interfaces

This article presents a fully integrated, wireless, RF-powered data transceiver for high-performance implants, such as neural interfaces. The design occupies a total volume of 1.6 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> with no need for an off-chip component. The integrated circuit (IC) receives power and downlink data with amplitude-shift-keying (ASK) modulation by an on-chip coil through an RF wireless link. For uplink data transmission, we designed a transmitter (TX) based on a power oscillator stage directly connected to an on-chip dipole antenna that supports various data rates with both on–off-keying (OOK) and ultrawideband (UWB) schemes. The radio includes a power receiver (RX) system that enables the IC to operate under various power budgets by adjusting the duty cycle of the TX. With a 25-dBm power TX at a 1-cm distance, the RX achieves a maximum data rate of 2.5 Mbps with a power consumption of 2.6 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula> . Also, the TX supports data rates of up to 150 Mbps with UWB modulation with a 15-cm operating range achieving an energy efficiency of 4.7 pJ/b. This work improves RX and TX energy inefficiencies by <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times 50$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times 2.3$ </tex-math></inline-formula> , respectively.

A Cloud-based Asset Tracking System for Hospitals Using Ultra-wideband Localization

Nosocomial infections are fatal diseases caused by microorganisms in the hospital environment. It has mortality rates of up to 70% in intensive care units. The most important way to fight this infection is to pay attention to the hygiene of the assets in the hospital. Within the scope of this paper, an IoT-based real-time advanced asset tracking system has been implemented. This system consists of three main components: Hand Hygiene Surveillance System, Device Tracking System, and Infection Control System. Providing hand hygiene in hospitals is critical for the prevention of infections. The proposed Hygiene Surveillance System provides hand hygiene control in intensive care units and neonatal services, which are the areas with the highest risk of infections. Received signals from ultrawide-band (UWB) modules are processed by a designed positioning algorithm. While competitors are insufficient in many scenarios because of the 1-2 m precision positioning, the proposed system provides a solution in these scenarios with 20-25 cm precision. Antibiotic-resistant nosocomial infection is difficult to treat, contagious, and fatal. These patients are kept in quarantine. During the transportation of these patients, end-to-end hygiene control is required. By using the developed Infection Control System, these patients will be followed end-to-end in real-time. Our system consists 3 main layers. In the first layer, the distributed IoT devices in the environment collect the broadcasted UWB and Bluetooth Low Energy (BLE) signals from the mobile nodes. The strength of the received signals is sent to the second layer which is responsible for calculating the location of mobile nodes based on the received signals from different anchor nodes. The detected locations are sent to the thir layer which provide the real time tracking system for the web and mobile applications. In this layer different technologies such as JSON, Ajax, Server Sent Events, WebSockets, and RestFul technologies are used to deliver the real time location data to the users.

UWB Based Relative Planar Localization with Enhanced Precision for Intelligent Vehicles

Along with the rapid development of advanced driving assistance systems for intelligent vehicles, essential functions such as forward collision warning and collaborative cruise control need to detect the relative positions of surrounding vehicles. This paper proposes a relative planar localization system based on the ultra-wideband (UWB) ranging technology. Three UWB modules are installed on the top of each vehicle. Because of the limited space on the vehicle roof compared with the ranging error, the traditional triangulation method leads to significant positioning errors. Therefore, an optimal localization algorithm combining homotopy and the Levenberg–Marquardt method is first proposed to enhance the precision. The triangular side lengths and directed area are introduced as constraints. Secondly, a UWB sensor error self-correction method is presented to further improve the ranging accuracy. Finally, we carry out simulations and experiments to show that the presented algorithm in this paper significantly improves the relative position and orientation precision of both the pure UWB localization system and the fusion system integrated with dead reckoning.

Ultrawideband (UWB)-based precise short-range localization for wireless power transfer to electric vehicles in parking environments.

As the necessity of wireless charging to support the popularization of electric vehicles (EVs) emerges, the development of a wireless power transfer (WPT) system for EV wireless charging is rapidly progressing. The WPT system requires alignment between the transmitter coils installed on the parking lot floor and the receiver coils in the vehicle. To automatically align the two sets of coils, the WPT system needs a localization technology that can precisely estimate the vehicle’s pose in real time. This paper proposes a novel short-range precise localization method based on ultrawideband (UWB) modules for application to WPT systems. The UWB module is widely used as a localization sensor because it has a high accuracy while using low power. In this paper, the minimum number of UWB modules consisting of two UWB anchors and two UWB tags that can determine the vehicle’s pose is derived through mathematical analysis. The proposed localization algorithm determines the vehicle’s initial pose by globally optimizing the collected UWB distance measurements and estimates the vehicle’s pose by fusing the vehicle’s wheel odometry data and the UWB distance measurements. To verify the performance of the proposed UWB-based localization method, we perform various simulations and real vehicle-based experiments.

A Novel V2V Cooperative Collision Warning System Using UWB/DR for Intelligent Vehicles.

The collision warning system (CWS) plays an essential role in vehicle active safety. However, traditional distance-measuring solutions, e.g., millimeter-wave radars, ultrasonic radars, and lidars, fail to reflect vehicles’ relative attitude and motion trends. In this paper, we proposed a vehicle-to-vehicle (V2V) cooperative collision warning system (CCWS) consisting of an ultra-wideband (UWB) relative positioning/directing module and a dead reckoning (DR) module with wheel-speed sensors. Each vehicle has four UWB modules on the body corners and two wheel-speed sensors on the rear wheels in the presented configuration. An over-constrained localization method is proposed to calculate the relative position and orientation with the UWB data more accurately. Vehicle velocities and yaw rates are measured by wheel-speed sensors. An extended Kalman filter (EKF) is applied based on the relative kinematic model to combine the UWB and DR data. Finally, the time to collision (TTC) is estimated based on the predicted vehicle collision position. Furthermore, through UWB signals, vehicles can simultaneously communicate with each other and share information, e.g., velocity, yaw rate, which brings the potential for enhanced real-time performance. Simulation and experimental results show that the proposed method significantly improves the positioning, directing, and velocity estimating accuracy, and the proposed system can efficiently provide collision warning.

Distance Measurements in UWB-Radio Localization Systems Corrected with a Feedforward Neural Network Model

An ultra-wideband (UWB) localization system is an alternative in a GPS-denied environment. However, a distance measurement with UWB modules using a two-way communication protocol induces an orientation-dependent error. Previous research studied this error by looking at parameters such as the received power and the channel response signal. In this paper, the neural network (NN) method for correcting the orientation-induced distance error without the need to calculate the signal strength, obtain the channel response or know any parameters of the antenna and the UWB modules is presented. The NN method utilizes only the measured distance and the tag orientation, and implements an NN model obtained by machine learning, using measurements at different distances and orientations of the two UWB modules. The verification of the experimental setup with 12 anchors and a tag shows that with the proposed NN method, 5 cm better root mean square error values (RMSEs) are obtained for the measured distance between the anchors and the tag compared to the calibration method that did not include orientation information. With the least-square estimator, 14 cm RMSE in 3D is obtained with the NN model corrected distances, with a 9 cm improvement compared to when raw distances are used. The method produces better results without the need to obtain the UWB module’s diagnostics parameters that are required to calculate the received signal strength or channel response, and in this way maintain the minimum packet size for the ranging protocol.

Narrowband and ultra-wideband modulation instability in nonlinear metamaterial waveguides

Waveguides based on metamaterials may exhibit strongly frequency-dependent nonlinearities. In this work, we focus on the phenomenon of modulation instability in this type of waveguide, departing from a new modeling equation that ensures strict conservation of both the energy and photon number of the parametric process. In particular, we analyse the case of a waveguide with a linearly frequency-dependent nonlinear coefficient, revealing unique features such as narrowband and ultra-wideband gain spectra and the suppression of the power cutoff giving rise to an ever-growing MI gain. These markedly distinct regimes are enabled by self-steepening (SS) and manifest themselves depending upon the magnitude and sign of the SS parameter. We believe these findings to be most relevant in the context of mid-IR supercontinuum sources.

MULTILATERATION UNDER FLIP AMBIGUITY FOR UAV POSITIONING USING ULTRAWIDE-BAND

Abstract. Ultrawide-band (UWB) ranging technology and multilateration techniques have recently been emerging solutions for positioning unmanned aerial vehicles (UAVs) in GNSS-denied environments. This solution offers cm-level ranging accuracy and considerable robustness to multipath receptions. UWB modules are commonly used in an anchor-based configuration; i.e., one UWB tag is mounted on the UAV, and several UWB anchors are installed on the ground. In real-world operational conditions, anchors can form a planar or a near-planar surface. This causes a geometric ambiguity, called flip ambiguity, in position estimation. Flip ambiguity can lead to considerable errors in the estimated position by multilateration. In this paper, we present a multilateration approach, which automatically resolves the flip ambiguity for UAV-positioning using UWB ranging. The proposed multilateration method first computes an algebraic solution through recursive least squares. If the initially estimated position is found to be flipped, then it is corrected by a symmetric reflection with respect to the anchor plane. Finally, the estimated position is refined by non-linear optimization. Extensive experiments in a real environment show that the proposed algorithm can effectively tackle the issue of flip ambiguity in multilateration, leading to a significant improvement in positioning accuracy.

A UWB-Based Indoor Positioning System Employing Neural Networks

Because of its high time-domain resolution, ultra-wideband (UWB) technology is capable of precise range measurement and has been applied in many accurate indoor positioning systems. This paper presents a practical indoor positioning and navigation system using the UWB modules we developed based on Decawave UWB chipset. In order to enhance the performance of the system in NLOS scenarios, a neural network approach is integrated. The feasibility of the combined approach is analysed and its accuracy is evaluated. The experiment results indicate that the neural network can maintain a stable accuracy no matter whether it is in an NLOS scenario and it is capable to identify the locations on two trajectories which are next to each other with very high confidence.