Ultra-wideband Signals Research Articles

ОЦЕНКА ВЛИЯНИЯ ПАРАМЕТРОВ СВЕРХШИРОКОПОЛОСНЫХ РАДИОСИГНАЛОВ НА ХАРАКТЕРИСТИКИ ИХ ПРИЕМА И ПЕРЕДАЧИ

The concepts of the narrowband parameter and the broadband indicator when using ultra-wideband signals are investigated, the main features of signal classification, as well as their advantages and disadvantages are formulated. The influence of the narrowband parameter on the characteristics of emission and reception of ultra-wideband signals is evaluated, and recommendations are formulated to improve the efficiency of their use in radiophysical and electronic applications.

A Wideband High-Gain Dielectric Horn-Lens Antenna for Wireless Communications and UWB Applications

A wideband high-gain dielectric horn-lens antenna (DHLA) for wireless communications and ultra-wideband (UWB) applications, featuring 122% fractional bandwidth, is presented. The antenna, consisting of a dielectric horn equipped with a spherical-axicon dielectric lens that increases and equalizes the gain within the operating band, is placed on a PCB featuring a wideband eight-shaped slot fed by a tapered microstrip line employed to excite the radiating system. The lens, integrated within the body of the dielectric horn, has the property of focusing the RF energy near its vertex on an extended frequency band, thus ensuring compact size, excellent field coupling with the antenna excitation system, and a significant increase of antenna gain. The antenna operates in the 3–12.4 GHz frequency range with relatively flat group delay, making it suitable for operating with narrowband, broadband, and impulsive UWB signals. The antenna can work properly without or with a metal reflector useful to enhance gain (up to 19 dBi), improve the front-to-back ratio, and reduce the impact of the antenna characteristics from the installation site. CST Studio Suite, implementing a full-wave locally conformal finite integration technique (FIT), was employed to design and characterize the antenna. The antenna characteristics estimated numerically were found to be in good agreement with the experimental results performed on an antenna prototype.

Broadband Microwave Photonic Channelizer with 18 Channels Based on Acousto-Optic Frequency Shifter

A microwave photonic channelizer can achieve instantaneous reception of ultra-wideband signals and effectively avoid electronic bottleneck; therefore, it can be perfectly applied to a wideband radar system and electronic warfare. In channelization schemes based on an optical frequency comb (OFC), the number of comb lines usually depends on that of the sub-channels. In order to improve the utilization rate of the comb lines of OFC, we propose a scheme to shift the frequency of OFC by using an acousto-optic frequency shifter (AOFS), which can obtain three times the number of sub-channels of the comb lines of an OFC. In order to simplify the experiment, only a three-line OFC is used in the experiment. A three-line local oscillator (LO) OFC is frequency-shifted up and down by two AOFSs, and nine optical LO signals with different frequencies are obtained, thereby realizing the simultaneous reception of eighteen sub-channels. The proposed scheme enjoys a large number of sub-channels and minimal channel crosstalk. Experimental results demonstrate that a 9-GHz bandwidth RF signal covering 10–19 GHz is divided into 18 sub-channels with a sub-bandwidth of 500 MHz. The image rejection ratio of the sub-channels is about 23 dB, and the spurious-free dynamic range (SFDR) of the receiver can reach 98 dB·Hz2/3.

Low-Cost UWB Based Real-Time Locating System: Development, Lab Test, Industrial Implementation and Economic Assessment.

This paper presents the technical development and subsequent testing of a Real-Time Locating System based on Ultra-Wideband signals, with the aim to appraise its potential implementation in a real industrial case. The system relies on a commercial Radio Indoor Positioning System, called Qorvo MDEK1001, which makes use of UWB RF technology to determine the position of RF-tags placed on an item of interest, which in turn is located in an area covered by specific fixed antennas (anchors). Testing sessions were carried out both in an Italian laboratory and in a real industrial environment, to determine the best configurations according to some selected performance indicators. The results support the adoption of the proposed solution in industrial environments to track assets and work in progress. Moreover, most importantly, the solution developed is cheap in nature: indeed, normally tracking solutions involve a huge investment, quite often not affordable above all by small-, medium- and micro-sized enterprises. The proposed low-cost solution instead, as demonstrated by the economic assessment completing the work, justifies the feasibility of the investment. Hence, results of this paper ultimately constitute a guidance for those practitioners who intend to adopt a similar system in their business.

UWB Positioning System Based on LSTM Classification With Mitigated NLOS Effects

It is known that an ultrawideband (UWB)-based indoor positioning system (IPS) has superior positioning performance and can meet the requirements of location-based services (LBSs) as the Internet of Things (IoT) applications. However, there is a limitation of UWB positioning when it is conducted at the nonline-of-sight (NLOS) channels degrading the UWB ranging accuracy at indoor environments. In this article, we propose an artificial intelligence (AI) applied UWB positioning system that can enhance the positioning performance by classifying channel conditions with channel impulse response (CIR) of the received UWB signal. The proposed system mitigates the positioning degradation caused by the NLOS situations by performing extended Kalman filter (EKF) localization and long short-term memory (LSTM) training of the observed channel status. The main feature of the proposed UWB positioning method is that it can be used even at unknown locations not trained with the LSTM model learning the channel status, because of our training strategy of not the position coordinates, but the UWB ranging error between UWB devices corresponding to CIR of the received UWB signal. This article provides the experimental setup and performance evaluation results of the proposed system. The evaluation results showed that the proposed AI-applied UWB positioning method significantly improved its accuracy performance compared with the existing positioning methods.

Microwave photonics matched filter for fast processing of ultra-wideband input signal

A scheme of a specialized analog processor implementing a microwave photonics correlation receiver in the form of a matched filter for processing an ultra-wideband microwave signal is proposed. The operation of such a filter is numerically investigated, its characteristics are found (accuracy of determining the position of the maximum of the output signal, potential performance).

An Ultrawideband System for Measuring the Dielectric Properties of Mineral Compounds in a Heat-Reaction Chamber at High Temperatures

A measurement system for the measurement of microwave dielectric properties of mineral compounds at temperatures up to +1000°C is presented. It includes the simultaneous measurement of mass and temperature. Samples volumes in the range 0.01 to 0.1 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> can be studied. The system comprises a heat reaction chamber on a mass scale with mounted ultra-wideband (UWB) radio sensors and temperature probes. The complex refractive index is determined from the UWB signals using a technique with windowing to suppress interference and fitting of a modelled signal to the experimental ones. The developed method is validated by measuring the complex refractive index of water from +82°C down to +23°C and comparing with literature values. The systems is used to study calcination of limestone, i.e. the chemical decomposition of CaCO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> to CaO and CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> when heated up to +1000°C. The chemical decomposition is clearly seen as a decrease in mass and as significant changes in the complex refractive index. The system could be used also for other mineral compounds and other types of materials.

Robust LOS/NLOS Identification for UWB Signals Using Improved Fuzzy Decision Tree Under Volatile Indoor Conditions

Ultra-wideband (UWB) is a very promising indoor wireless positioning technology. However, in the harsh and volatile indoor environment, the propagation of UWB signals is vulnerable to non-line-of-sight (NLOS) conditions, and the contaminated range measurements will degrade the accuracy for UWB localization. Therefore, it is necessary to identify LOS/NLOS. Recent studies mainly focus on the identification of UWB signal propagation conditions by using channel impulse response (CIR) or extracted channel statistical features. However, these studies usually only focus on specific indoor environment or stable indoor conditions. In fact, the indoor environment is harsh and changeable. In order to deal with the dynamic and uncertain information of the indoor environments, this paper proposes a robust method to identify LOS/NLOS using fuzzy decision tree (FDT) based on Bayesian optimization. The proposed method first extracts the classification features from the CIRs, and then fuzzifies the features. Finally, it combines Bayesian optimization to construct the FDT, so as to identify the propagation conditions of UWB signals. The experimental results show that the identification accuracy of the proposed method is higher than 90 % in both static and dynamic experiments, and the overall performance is excellent. Compared with other methods, it has certain advantages and robustness.

Microwave Photonics Matched Filter for the Rapid Processing of Ultra-Wideband Input Signals

Microwave Photonics Matched Filter for the Rapid Processing of Ultra-Wideband Input Signals

Spatiotemporal Search for Pulsed Radiation in the Photon Flux Detection Mode with Prolonged Observation Time of the Decomposition Element

The development of science and technologies of microwave frequencies (UHF) has contributed to the fact that the use of ultrawideband (UWB) pulsed signals has emerged as a separate scientific and technical area of radiophysics, requiring a deeper study of the methods of formation, emission, reception and processing of such signals. Aperture radiators are mainly used to transmit UWB signals. This type of emitters is a variety of modifications of mirror antennas, horn antennas of various shapes and profiles, open waveguides, planar and conformal antenna arrays, as well as lens antennas. The classical theory of analysis of radiation and propagation of electromagnetic signals is well known, but its application to the synthesis of UWB emitters in the time domain often becomes too cumbersome and incorrect. Progress in the fields of radar, communications, and radio astronomy in the 1960s stimulated the creation of aperture theory based on physical optics approaches. This theory makes it possible to analyze and calculate the characteristics of mirror radiators and antenna arrays with sufficient accuracy for practical application. It is often possible to use the aperture theory to analyze some horn emitters that have a large radiation surface relative to the spatial dimensions of pulsed signals.

Design and Analysis of Impulse Radio (IR) Based UWB Transmitter with Antenna

The use of ultra-wideband (UWB) in target detection, radar and wireless connectivity, specifically in the medical world, has attracted a lot of attention. The concept that the IR-UWB system does not necessarily require carrier signals is one of its most appealing features. IR-UWB can transmit information using short Gaussian monocycle pulses. In light of these advantages, this paper proposes a novel UWB transmitter system which consists of UWB signal generating circuits and UWB antenna, which work together to create entire UWB transmitter. It is based on impulses and has a simple architecture with low power consumption. The proposed transmitter is realized in Cadence tools with 90nm CMOS technology and proposed UWB antenna is simulated using Advanced Design System (ADS) simulator software. In addition, the transmitter circuit and the antenna are co-simulated using ADS software. The illustrated UWB transmitter uses a low-power supply and generates pulse amplitude with pulse duration of for the Gaussian monocycle pulse. Due to its increased output voltage swing and reduced power consumption when comparing to other circuits, the proposed architecture is functional and suitable for use in short-range wireless networks and medical applications.

6G-oriented ultra-wideband fiber-THz-fiber seamless converged communication system: architecture, key techniques and verification

Terahertz (THz) communication is widely regarded as a key component of the future 6G mobile communication system. This paper proposes a novel ultra-wideband fiber-THz-fiber seamless converged real-time architecture that fully exploits the commercially mature digital coherent optical module (DCO) to realize ultra-high capacity THz real-time wireless communication by conducting a comparative analysis for some of the main existing technical routes of THz up- and down-conversion in THz wireless communication systems. (1) The proposed architecture employs the techniques of dual-polarization photonic up-conversion for THz generation and hybrid optoelectronic down-conversion for THz reception, respectively, to enable seamless integration of optical fiber and THz communications. (2) Due to the limited bandwidth of the optoelectronic devices, multi-dimensional modulation techniques are adopted for ultra-wideband terahertz signals to improve the spectral efficiency and transmission capacity. (3) An intelligent nonlinear joint compensation technique based on deep neural network (DNN) is proposed, which can effectively improve the signal-to-noise ratio of the time-varying hybrid fiber-THz-fiber channel. Based on the above-mentioned investigations, we for the first time realize the photonics-aided record-high 100/200 GbE real-time THz wireless transmission at 360 (∼) 430 GHz band, with a capacity of 10 to 20 times that of 5G. The proposed fiber-THz-fiber architecture can realize the smooth conversion between high-speed THz signal and lightwave signal. Furthermore, the architecture can significantly reduce research complexity and development costs and thus greatly accelerate the commercialization of 6G THz technology by highly reusing commercial DCO modules, which is compatible with the physical layer transmission protocols such as IEEE 802.3 and ITU-T G.798. Finally, this paper discusses some potential research and development directions for higher-capacity, longer-distance, and more-integrated fiber-THz-fiber seamless communication.

Resilient tightly coupled INS/UWB integration method for indoor UAV navigation under challenging scenarios

Based on the high positioning accuracy, low cost and low-power consumption, the ultra-wide-band (UWB) is an ideal solution for indoor unmanned aerial vehicle (UAV) localization and navigation. However, the UWB signals are easy to be blocked or reflected by obstacles such as walls and furniture. A resilient tightly-coupled inertial navigation system (INS)/UWB integration is proposed and implemented for indoor UAV navigation in this paper. A factor graph optimization (FGO) method enhanced by resilient stochastic model is established to cope with the indoor challenging scenarios. To deal with the impact of UWB non-line-of-sight (NLOS) signals and noise uncertainty, the conventional neural net-works (CNNs) are introduced into the stochastic modelling to improve the resilience and reliability of the integration. Based on the status that the UWB features are limited, a ‘two-phase’ CNNs structure was designed and implemented: one for signal classification and the other one for measurement noise prediction. The proposed resilient FGO method is tested on flighting UAV platform under actual indoor challenging scenario. Compared to classical FGO method, the overall positioning errors can be decreased from about 0.60 m to centimeter-level under signal block and reflection scenarios. The superiority of resilient FGO which effectively verified in constrained environment is pretty important for positioning accuracy and integrity for indoor navigation task.

ECG-grained Cardiac Monitoring Using UWB Signals

With the development of wireless sensing, researchers have proposed many contactless vital sign monitoring systems, which can be used to monitor respiration rates, heart rates, cardiac cycles and etc. However, these vital signs are ones of coarse granularity, so they are less helpful in the diagnosis of cardiovascular diseases (CVDs). Considering that electrocardiogram (ECG) is an important evidence base for the diagnoses of CVDs, we propose to generate ECGs from ultra-wideband (UWB) signals in a contactless manner as a fine-grained cardiac monitoring solution. Specifically, we analyze the properties of UWB signals containing heartbeats and respiration, and design two complementary heartbeat signal restoration methods to perfectly recover heartbeat signal variation. To establish the mapping between the mechanical activity of the heart sensed by UWB devices and the electrical activity of the heart recorded in ECGs, we construct a conditional generative adversarial network to encode the mapping between mechanical activity and electrical activity and propose a contrastive learning strategy to reduce the interference from noise in UWB signals. We build the corresponding cardiac monitoring system named RF-ECG and conduct extensive experiments using about 120,000 heartbeats from more than 40 participants. The experimental results show that the ECGs generated by RF-ECG have good performance in both ECG intervals and morphology compared with the ground truth. Moreover, diseases such as tachycardia/bradycardia, sinus arrhythmia, and premature contractions can be diagnosed from the ECGs generated by our RF-ECG.

The Development and Progress of the UWB Physical Layer.

Ultra-wideband (UWB) technology has been applied in many fields, such as radar and indoor positioning, because of its advantages of having a high transmission rate, anti-multipath interference, and good concealment. In the UWB physical layer, the transmitting link, including an encoder and a pulse generator, is used to improve the anti-interference ability of the signal, while the receiving link, including a receiver and a decoder, can correct the error signal. Therefore, the performance of the UWB physical layer can obviously affect the speed and quality of UWB signal transmission. In this paper, the structure and performance of the codec and transceiver of the UWB physical layer are introduced and compared. In addition, some typical architectures and features are summarized and discussed, which provides a valuable reference and suggestions for the design of the UWB physical layer. Finally, the outlook of the UWB physical layer is presented: its development direction mainly includes high speed, low power consumption, and fewer hardware resources.

МЕТОД ГЕНЕРАЦИИ СВЕРХШИРОКОПОЛОСНЫХ СВЧ-СИГНАЛОВ С ЛИНЕЙНО-ЧАСТОТНОЙ МОДУЛЯЦИЕЙ НА ОСНОВЕ САМОГЕТЕРОДИНИРОВАНИЯ ИЗЛУЧЕНИЯ ЛАЗЕРНОГО ДИОДА

In this paper, microwave photonic technique of ultrawideband linearly frequency modulated signals generation is proposed. The proposed method based on direct modulation of the laser diode current, which provides a periodic change in the emission frequency. The Michelson interferometer summarizes laser signal and its replica with time delay exceeding 10 ms, which, in turn, is defined by time difference between arms. Optoelectronic conversion is performed in high-speed high-power photodiode. The proposed approach makes it possible to generate microwave signals with linear frequency modulation in the frequency range up to several tens of gigahertz by means of laser pump current modulation in the frequency range less than 100 MHz. The method of ultra-wideband microwave signals generation is implemented using a Michelson fiber-optic interferometer with Faraday mirrors. Such interferometer topology provides a doubling of the path length, and reduced gyroscopic effects due to a counter-propagating double pass. Changing the parameters of the generated microwave ultrawideband signals with frequency modulation is achieved by pump current shape and amplitude control. It is also proposed to use real-time oscilloscope without need of changing of the internal structure of such generator to pre-tune it. Time-frequency analysis is used to extract frequency versus time dependence. By so doing, direct impulse response estimation is performed. This method allows to characterize laser diode frequency response for arbitrary microwave waveform generation by means of pump current waveform calculation from experimental data.

Raditing-Measuring Complex for Studying the Passage of Ultrawideband Signals in the Atmosphere and Ionosphere of the Earth

Raditing-Measuring Complex for Studying the Passage of Ultrawideband Signals in the Atmosphere and Ionosphere of the Earth

Study of the possibility of implementing a remote-controlled robotic system in a closed volume of great length

A technique for evaluating the efficiency of using ultra-wideband pulses (UWB) for signal transmission by digital modems in a closed space is proposed. The studies were carried out for the variant of approximation of the ultra-wideband signal by the Gaussian function. Approximation by a Gaussian monocycle is adopted for the radiated electromagnetic signal. Analytical expressions are given for calculating the width of the spectrum of the signal under study. Taking into account the obtained spectral characteristics, the calculation of the signal energy as a whole and in the given frequency bands was carried out. A comparative quantitative assessment of the energy efficiency of an ultra-wideband signal and a short radio pulse has been carried out.

A Succinct Method for Non-Line-of-Sight Mitigation for Ultra-Wideband Indoor Positioning System.

Ultra-wideband (UWB) is a promising indoor position technology with centimetre-level positioning accuracy in line-of-sight (LOS) situations. However, walls and other obstacles are common in an indoor environment, which can introduce non-line-of-sight (NLOS) and deteriorate UWB positioning accuracy to the meter level. This paper proposed a succinct method to identify NLOS induced by walls and mitigate the error for improved UWB positioning with NLOS. First, NLOS is detected by a sliding window method, which can identify approximately 90% of NLOS cases in a harsh indoor environment. Then, a delay model is designed to mitigate the error of the UWB signal propagating through a wall. Finally, all the distance measurements, including LOS and NLOS, are used to calculate the mobile UWB tag position with ordinary least squares (OLS) or weighted least squares (WLS). Experiment results show that with correct NLOS indentation and delay model, the proposed method can achieve positioning accuracy in NLOS environments close to the level of LOS. Compared with OLS, WLS can further optimise the positioning results. Correct NLOS indentation, accurate delay model and proper weights in the WLS are the keys to accurate UWB positioning in NLOS environments.

Эффект «волновода» при распространении сверхширокополосных сигналов в помещении

“Waveguide” effect that occurs by indoor propagation of ultrawideband signals is shown. The effect exhibits itself in the absence of interference factor of signal dissipation at any distance. Unlike outdoor propagation, the signal attenuation in multipath indoor environment is similar to free space. The effect occurs due to reflections of the incident wave from paired opposite surfaces, e.g., floor – ceiling, parallel walls. As a result, the distance range of indoor ultrawideband communications is essentially higher than outdoors. The effect is simulated in a three-ray reflection model.