Improving the Structure of a Signal Used for Real-Time Calibrating of the Receiving Channels of Digital Transceiver Modules in Digital Phased Antenna Arrays

Introduction. Modern digital phased array antenna (DPAA) systems incorporate a large number of identical transceiver modules (TMs). These modules require real-time calibration with a high level of accuracy. In a previous work, we proposed a real-time calibration method for all receiver channels, which is based on the use of a calibration signal (CalSig) of the same frequency spectrum as the reflected signal and modulated in phase and amplitude by BPSK and OOK codes, respectively. This method was found to have a number of advantages over conventional approaches. However, the use of the same CalSig sample for all receiving channels increases the noise power gain at the output of a digital beam-forming unit (DBU). To overcome this limitation, we set out to improve the structure of CalSigs by making them pseudo-orthogonal. As a result, the noise power gain at the DBU output can be significantly reduced compared to that obtained in our previous work.Aim. To propose an improved design of a controlled amplitude modulation code OOK generator, which allows creation of pseudo-orthogonal CalSigs. As a result, the noise power gain at the output will increase insignificantly, thus having no negative effect on the quality of digital beam forming, signal processing and calibration.Materials and methods. Theory of system engineering and technology; theory of digital signal processing; system analysis; mathematical modeling.Results. An improved CalSig for calibrating the receiving channels of TMs was obtained. A structural diagram allowing the formation of pseudo-orthogonal CalSigs was synthesized.Conclusions. We proposed a new approach to improving the structure of signals used for real-time calibrating the DPAA receiving channels. A structural diagram of an amplitude-modulated OOK code generator for pseudo-orthogonal CalSigs was developed.Introduction. Modern digital phased array antenna (DPAA) systems incorporate a large number of identical transceiver modules (TMs). These modules require real-time calibration with a high level of accuracy. In a previous work, we proposed a real-time calibration method for all receiver channels, which is based on the use of a calibration signal (CalSig) of the same frequency spectrum as the reflected signal and modulated in phase and amplitude by BPSK and OOK codes, respectively. This method was found to have a number of advantages over conventional approaches. However, the use of the same CalSig sample for all receiving channels increases the noise power gain at the output of a digital beam-forming unit (DBU). To overcome this limitation, we set out to improve the structure of CalSigs by making them pseudo-orthogonal. As a result, the noise power gain at the DBU output can be significantly reduced compared to that obtained in our previous work.Aim. To propose an improved design of a controlled amplitude modulation code OOK generator, which allows creation of pseudo-orthogonal CalSigs. As a result, the noise power gain at the output will increase insignificantly, thus having no negative effect on the quality of digital beam forming, signal processing and calibration.Materials and methods. Theory of system engineering and technology; theory of digital signal processing; system analysis; mathematical modeling.Results. An improved CalSig for calibrating the receiving channels of TMs was obtained. A structural diagram allowing the formation of pseudo-orthogonal CalSigs was synthesized.Conclusions. We proposed a new approach to improving the structure of signals used for real-time calibrating the DPAA receiving channels. A structural diagram of an amplitude-modulated OOK code generator for pseudo-orthogonal CalSigs was developed

無線センサネットワークのための超低消費電力と高感度CMOS RF受信機に関する研究

Wireless sensor networks (WSN) have been applied in wide range of applications and proved the more and more important contribution in the modern life. In order to evaluate a WSN, many metrics are considered such as cost, latency, power or quality of service. However, since the sensor nodes are usually deployed in large physical areas and inaccessible locations, the battery change becomes impossible. In this scenario, the power consumption is the most important metric. In a sensor node, the RF receiver is one of the communication devices, which consume a vast majority of power. Therefore, this thesis studies ultra low power RF receivers for the long lifetime of the sensor nodes. Currently, the WSNs use various frequency bands. However, for low power target, the sub-GHz frequency bands are preferred. In this study, ultra-low power 315 MHz and 920 MHz receivers will be proposed for short-range applications and long-range applications of the WSNs respectively. To achieve ultra-low power target, the thesis considers some issues in architecture, circuit design and fabrication technology for suitable choices. After considering different receiver architectures, the RF detection receiver with the On-Off-Keying (OOK) modulation is chosen. Then the thesis proposes solutions to reduce power consumption and concurrently guarantee high sensitivity for the receivers so that they can communicate at adequate distances for both short and long-range applications. First, a 920 MHz OOK receiver is designed for the long-range WSN applications. Typically, the RF amplifiers and local oscillators consume the most of power of RF receivers. In the RF detection receivers, the local oscillators are eliminated, however, the power consumption of the RF amplifiers is still dominant. By reducing the RF gain or removing the RF amplifier, the power consumption of the receivers can be reduced drastically. However, in this case the sensitivity is very limited. In order to overcome the trade-off between power consumption and sensitivity, the switched bias is applied to the RF amplifiers to reduce their power consumption substantially while guaranteeing high RF gain before RF detection. As a result, the receiver consumes only 53 W at 0.6 V supply with -82 dBm sensitivity at 10 kbps data rate. Next, an OOK receiver operating at 315 MHz for the short-range WSN applications with low complexity is proposed. In this receiver, the RF amplifier is controlled to operate intermittently for power reduction. Furthermore, taking advantage of the low carrier frequency, a comparator is used to convert the RF signal to a rail-to-rail stream and then data is demodulated in the digital domain. Therefore, no envelope detector or baseband amplifiers is required. The architecture of the receiver is verified by using discrete RF modules and FPGAs before it is designed on CMOS technology. By simulation with the physical layout, the 315 MHz OOK receiver consumes 27.6 W at 200 kbps and achieves -76.4 dBm sensitivity. Finally, the Synchronized-OOK (S-OOK) modulation scheme is proposed and then an S-OOK receiver operating in the 315 MHz frequency is developed to reduce power consumption more deeply. The S-OOK signal contains not only data but also clock information. By generating a narrow window, the RF front-end is enabled to receive signal only in a short period, therefore, power consumption of the receiver is reduced further. In addition, thank to the clock information contained in the input signal, the data and corresponding clock are demodulated simultaneously without a clock and data recovery circuit. The architecture of the S-OOK receiver is also verified by using discrete RF modules and FPGAs, then VLSI design is carried out. Physical layout simulation shows that the receiver can achieve -76.4 dBm sensitivity, consumes 8.39 W, 4.49 W, 1.36 W at 100 kbps, 50 kbps and 10 kbps respectively. In conclusion, with the objective is to look for solutions to minimize power consumption of receivers for extending the lifetime of sensor nodes while guaranteeing high sensitivity, this study proposed novel receiver architectures, which help reduce power consumption significantly. If using the coin battery CR2032 for power supply, the 920 MHz OOK receiver can work continuously in 1.45 years with communication distance of 259 meters; the 315 MHz OOK receivers can work continuously in 2.8 years with approximately 19 meters communication distance in free space. Whereas, the 315 MHz S-OOK receiver with the minimum power consumption of 1.36 W is suitable for batteryless sensor nodes.電気通信大学201

An integrated localization-navigation scheme for distance-based docking of UAVs

In this paper we study the distance-based docking problem of unmanned aerial vehicles (UAVs) by using a single landmark placed at an arbitrarily unknown position. To solve the problem, we propose an integrated estimation-control scheme to simultaneously achieve the relative localization and navigation tasks for discrete-time integrators under bounded velocity: a nonlinear adaptive estimation scheme to estimate the relative position to the landmark, and a delicate control scheme to ensure both the convergence of the estimation and the asymptotic docking at the given landmark. A rigorous proof of convergence is provided by invoking the discrete-time LaSalle's invariance principle, and we also validate our theoretical findings on quadcopters equipped with ultra-wideband ranging sensors and optical flow sensors in a GPS-less environment

A Machine Learning-based Approach to Vietnamese Handwritten Medical Record Recognition

Handwritten text recognition has been an active research topic within computer vision division. Existing deep-learning solutions are practical; however, recognizing Vietnamese handwriting has shown to be a challenge with the presence of extra six distinctive tonal symbols and extra vowels. Vietnam is a developing country with a population of approximately 100 million, but has only focused on digitalization transforms in recent years, and so Vietnam has a significant number of physical documents, that need to be digitized. This digitalization transform is urgent when considering the public health sector, in which medical records are mostly still in hand-written form and still are growing rapidly in number. Digitization would not only help current public health management but also allow preparation and management in future public health emergencies. Enabling the digitalization of old physical records will allow efficient and precise care, especially in emergency units. We proposed a solution to Vietnamese text recognition that is combined into an end-to-end document-digitalization system. We do so by performing segmentation to word-level and then leveraging an artificial neural network consisting of both convolutional neural network (CNN) and a long short-term memory recurrent neural network (LSTM) to propagate the sequence information. From the experiment with the records written by 12 doctors, we have obtained encouraging results of 6.47% and 19.14% of CER and WER respectively

SPINS: Structure Priors aided Inertial Navigation System

Although Simultaneous Localization and Mapping (SLAM) has been an active research topic for decades, current state-of-the-art methods still suffer from instability or inaccuracy due to feature insufficiency or its inherent estimation drift, in many civilian environments. To resolve these issues, we propose a navigation system combing the SLAM and prior-map-based localization. Specifically, we consider additional integration of line and plane features, which are ubiquitous and more structurally salient in civilian environments, into the SLAM to ensure feature sufficiency and localization robustness. More importantly, we incorporate general prior map information into the SLAM to restrain its drift and improve the accuracy. To avoid rigorous association between prior information and local observations, we parameterize the prior knowledge as low dimensional structural priors defined as relative distances/angles between different geometric primitives. The localization is formulated as a graph-based optimization problem that contains sliding-window-based variables and factors, including IMU, heterogeneous features, and structure priors. We also derive the analytical expressions of Jacobians of different factors to avoid the automatic differentiation overhead. To further alleviate the computation burden of incorporating structural prior factors, a selection mechanism is adopted based on the so-called information gain to incorporate only the most effective structure priors in the graph optimization. Finally, the proposed framework is extensively tested on synthetic data, public datasets, and, more importantly, on the real UAV flight data obtained from a building inspection task. The results show that the proposed scheme can effectively improve the accuracy and robustness of localization for autonomous robots in civilian applications.Comment: 14 pages, 14 figure

A Fuzzy LQR PID Control for a Two-Legged Wheel Robot with Uncertainties and Variant Height

This paper proposes a fuzzy LQR PID control for a two-legged wheeled balancing robot for keeping stability against uncertainties and variant heights. The proposed control includes the fuzzy supervisor, LQR, PID, and two calibrations. The fuzzy LQR is conducted to control the stability and motion of the robot while its posture changes with respect to time. The fuzzy supervisor is used to adjust the LQR control according to the robotic height. It consists of one input and one output. The input and output have three membership functions, respectively, to three postures of the robot. The PID control is used to control the posture of the robot. The first calibration is used to compensate for the bias value of the tilting angle when the robot changes its posture. The second calibration is applied to compute the robotic height according to the hip angle. In order to verify the effectiveness of the proposed control, a practical robot with the variant height is constructed, and the proposed control is embedded in the control board. Finally, two experiments are also conducted to verify the balancing and moving ability of the robot with the variant posture

The Effectiveness of Knowledge Management Systems in Improving Teaching Motivation among Vietnamese Higher Education Staffs

This study investigates the dynamic relationship between knowledge management systems, particularly emphasizing knowledge acquisition and dissemination, and their impact on academic staff's teaching motivation. By employing the Bayesian Mindsponge Framework (BMF), data from 676 academic staff at higher education institutions in Vietnam was analyzed, revealing a complex interplay of factors. Notably, positive associations were found between knowledge acquisition, knowledge dissemination, and teaching motivation. However, the interaction effect of knowledge acquisition and knowledge dissemination appeared to be negatively associated with teaching motivation. This suggests the possible existence of a resource curse of knowledge in improving staff’s teaching motivation. It is recommended that the knowledge systems are refined to reduce complexity and that staff are trained with better knowledge processing methods for reducing resource curse risks

Exploring Italian Consumers’ Willingness to Pay for Sustainable Fashion: The Roles of Eco-Consciousness and Vintage Preference

Studying the psychology behind the purchase of eco-friendly products and second-hand items can offer valuable insights to promote sustainable consumer behavior. This paper examines factors influencing Italian consumers’ willingness to pay regarding bio-based clothing and second-hand items. Drawing from data collected from 402 Italian participants, we examine how motivations and socio-demographic factors are associated with willingness to pay in the context of sustainable fashion. Our findings reveal that motivations related to environmental concerns are positively associated with consumers’ willingness to pay higher premiums for bio-based clothing. Higher income and education levels are also associated with the willingness to pay higher premiums. Meanwhile, motivation related to vintage appeal is associated with lower desired discounts for second-hand items, particularly among older consumers. Gender differences also influence discount preferences, with men seeking larger discounts on second-hand clothing compared to women. By providing insights into Italian consumers’ sustainable fashion choices, this study offers implications for businesses, policymakers, and researchers aiming to promote eco-conscious consumption and sustainability in the fashion industry

When Intervention Becomes Imperative: A Case Report of Spontaneous Vulvar Edema During Pregnancy

Spontaneous idiopathic vulvar edema during the second trimester is a rare condition. The approach to managing this condition involves relieving symptoms, identifying underlying causes, and implementing appropriate treatment. Managing such cases during pregnancy is challenging because of concerns for potential adverse fetal outcomes. Conservative management expects the condition to be relieved spontaneously postpartum, whereas invasive treatment offers a more rapid resolution. Treatment choices are controversial because each method has its pros and cons and influences the delivery process to a certain extent. Surgical drainage becomes a viable option when patients are not responsive to medications. We report a case of spontaneous massive vulvar edema in a 22-year-old primigravida in her 23rd week of pregnancy. After ruling out other notable causes of vulvar edema, we decided to intervene using an invasive procedure because she complained of progressive symptoms and discomfort. Subsequently, the edema subsided postprocedure, and the patient experienced successful labor with no complications. This report aims to alert clinicians that drainage attempts should be considered in pregnant patients with worsening symptoms