Ultra-wideband Signals Research Articles

Квазиправдоподобный алгоритм оценки частоты сверхширокополосного квазирадиосигнала с неизвестной длительностью

The quasi-likelihood frequency estimation algorithm of an ultra-wideband quasi-radio signal with an unknown duration, observed with white Gaussian noise, is studied. When synthesizing the frequency estimation algorithm, instead of an unknown duration, some of its expected value was used. The dependence of the variance of the frequency estimate of an ultra-wideband quasi-radio signal on the signal-to-noise ratio for various values of the duration detuning and the dependence of the frequency estimate bias on the duration detuning for various values of the narrowband parameter are obtained. It has been established that the duration detuning has a significant effect on the efficiency of frequency estimation of an ultra-wideband quasi-radio signal, while at large values of the narrowband parameter, the obtained expressions coincide with the known expressions for the variance and bias of the frequency estimate of narrowband radio signal. Recommendations on the use of the synthesized algorithm in practical applications are formulated.

Low-Complexity Joint Angle of Arrival and Time of Arrival Estimation of Multipath Signal in UWB System.

In an ultra-wideband (UWB) system, the two-dimensional (2D) multiple signal classification (MUSIC) algorithms based on high-precision 2D spectral peak search can jointly estimate the time of arrival (TOA) and angle of arrival (AOA). However, the computational complexity of 2D-MUSIC is very high, and the corresponding data model is only based on the dual antennas. To solve these problems, a low-complexity algorithm for joint AOA and TOA estimation of the multipath ultra-wideband signal is proposed. Firstly, the dual antenna sensing data model is extended to the antenna array case. Then, based on the array-sensing data model, the proposed algorithm transforms the 2D spectral peak search of 2D-MUSIC into a secondary optimization problem to extract the estimation of AOA via only 1D search. Finally, the acquired AOA estimations are brought back, and the TOA estimations are also obtained through a 1D search. Moreover, in the case of an unknown transmitted signal waveform, the proposed method can still distinguish the main path signal based on the time difference of arrival of different paths, which shows wider applications. The simulation results show that the proposed algorithm outperforms the Root-MUSIC algorithm and the estimation of signal parameters using the rotational invariance techniques (ESPRIT) algorithm, and keeps the same estimation accuracy but with greatly reduced computational complexity compared to the 2D-MUSIC algorithm.

Low-Cost Real-Time Locating System Solution Development and Implementation in Manufacturing Industry

The present work originates from a previous study in which a low-cost Real-Time Locating System (RTLS) based on Ultra-Wideband signals was developed and tested both in a laboratory and in a real industrial environment for assessing its performance and determining the best configuration, according to some selected KPIs. Starting from the future research directions depicted, the evolution herein presented is twofold. First, tests performed in the laboratory are refined and deepened in terms of (i) different anchors’ arrangements and orientation; (ii) the increased number of tested tags; and (iii) the tags’ battery capacity test. Second, the development and deployment of the industrial solution as well is improved by means of a case for hosting tags to be positioned on the asset to be tracked, realized through 3D printing, in line with the industrial context requirements. Finally, an economic analysis is performed so as to demonstrate the convenience of the investment and the feasibility of the solution. Results are positive and promising in terms of both economic sustainability and implementation of the system in a real industrial environment and may constitute guidelines for practitioners and managers.

Measurement of high-power transient electromagnetic pulse field with integrated photonic electric-field sensor

To satisfy certain special requirements for high-power transient electromagnetic pulse (EMP) field measurements, such as high electric field intensity, broad bandwidth, fast rise time, and compact size, here is described an integrated electro-optic sensor. The frequency response in the range from 100 kHz to 12 GHz and the time-domain input/output characteristics of a sub-nanosecond EMP field with an intensity from 5 to 100 kV/m were experimentally characterized. The sensor was demonstrated to measure the time-domain waveform of the ultrawideband EMP field signals with a rise time of 0.35 ns and bandwidth of 1 GHz. In addition, the minimal detectable electric field strength was 16 mV/m/Hz1/2 in the frequency domain, and an intense sub-nanosecond electromagnetic pulse with a peak amplitude of 100 kV/m was observed in the time domain. The reported sensor is expected to be broadly used for intense EMP measurements.

A Non-Line-of-Sight Mitigation Method for Indoor Ultra-Wideband Localization With Multiple Walls

Ultra-wideband (UWB) ranging techniques can provide accurate distance measurement in line-of-sight (LOS) conditions. However, various walls and obstacles in indoor non-line-of-sight (NLOS) environments, which obstruct the direct propagation of UWB signals, can generate significant ranging errors. Due to the complex through-wall UWB signal propagation, most conventional studies simplify the ranging error model by assuming that the incidence angle is zero or the relative permittivities for different walls are the same to improve the through-wall UWB localization performance. Considering walls are different in realistic settings, this paper presents a through-multiple-wall NLOS mitigation method for UWB indoor positioning. First, spatial geometric equilibrium equations of UWB through-wall propagation and a numerical method are developed for the precise modeling of UWB through-wall ranging errors. Then, calculated error maps are determined numerically without field measurements. Finally, the determined error maps are combined with a gray wolf optimization algorithm for localization. The proposed method is evaluated via field experiments with four rooms, three walls, and six penetration cases. The results demonstrate that the method can strongly mitigate the multi-wall NLOS effects on the performance of UWB positioning systems. This solution can reduce project costs and number of power supplies for UWB indoor positioning applications.

QTT Ultra-wideband Signal Acquisition and Baseband Data Recording System Design Based on the RFSoC Platform

Abstract The 110 m QiTai radio Telescope (QTT) will be equipped with multiple Ultra-WideBand (UWB) receivers in the primary and Gregory focus to achieve continuous frequency coverage from 270 MHz to 115 GHz, which poses great challenges to signal acquisition, transmission, and real-time processing. Aiming at 10 GHz and above full-bandwidth acquisition and multi-scientific processing for the QTT UWB signals, an experimental system with high-speed signal acquisition, 100 Gb network multi-path distribution, and fast recording is designed by using advanced direct RF-sampling technology and heterogeneous architecture. The system employs a ZCU111 board to digitize dual-polarization signals with a sampling rate of 4.096 GigaSamples-Per-Second and 12-bit quantization. The collected wideband signals are channelized into 2048 chunks, which are then assembled into 16 sets of digital narrow basebands with 128 MHz bandwidth and transmitted to the processing servers through two 100 Gb ports. A HASPIPE pipeline, UWB_HASHPIPE is designed to receive and store multiple subbands in parallel. Data distribution links can be flexibly configured based on IP addresses and port numbers. The system is verified by pulsar observation experiments on the Nanshan 26 m telescope. 512 MHz bandwidth is selected from the collected L-band receiver signals and recorded in VDIF file format with 8 parallel instances. The test results show that the data integrity is excellent, and the signal-to-noise ratio of the band-merged pulsar profile is stronger than single subband data. This paper provides a high-performance and flexible solution for the design of versatile UWB backends. Meanwhile, the developed platform can be integrated into QTT backends for baseband data collection and Very Long Baseline Interferometry observation.

ИССЛЕДОВАНИЕ МЕТОДА БЛИЖНЕПОЛЬНОЙ СВЧ ТОМОГРАФИИ ПАРАМЕТРОВ ЛЕГКИХ

The results of theoretical and experimental studies of near-field microwave tomography of inhomogeneities in the parameters of relative blood content and air filling of the lungs are presented. Methods and algorithms for solving inverse problems of 3D tomography of the mentioned parameters of the lungs are proposed based on the data of pulse and multifrequency multisensory measurements of the scattered signal, as well as on the basis of the multi-position application of the previously developed 1D tomography (profiling) method. An experimental study of this method was carried out: based on the data of sequential bistatic measurements of the parameters of a scattered ultra-wideband pulse signal in a two-dimensional (square) region of the chest, a three-dimensional tomographic distribution of air content in the lungs in the inhalation phase was obtained.

Real-time signal processing method of ultra-wideband fuze using LSTM

The extraction of target features from the ultra-wideband (UWB) fuze echo signal and target recognition and distance determination are the key to controlling the precise detonation of the fuze. In this paper, a real-time signal processing method of UWB fuze based on Long Short-Term Memory (LSTM) network is proposed. The time domain and frequency domain features of echo signal are recognized through a small-scale LSTM network. Matlab is used to build the network model and simulation results show that the method can effectively avoid noise interference, correctly recognize the target signal, and avoid false alarm.

Strategy of building a wireless mobile communication system in the conditions of electronic counteraction

The subject of research in this article is the process of building a mobile communication system that operates under electronic countermeasures. The aim is to develop recommendations for building a wireless mobile communication system that operates effectively in a complex interfering electromagnetic environment. The strategy for building a mobile wireless communication system is based on the use of a grouping of low-altitude UAVs with ultra-wideband signal technology circulating in control and communication channels, with the integration of artificial intelligence elements into its structure. The objective of this study is to ensure the stable and secure operation of a wireless mobile communication system despite electronic countermeasures. The methods of analytical, temporal positional pulse coding, and fuzzy logical inference were used to make decisions on the transfer of service in the network. The following results were obtained. A strategy for building a wireless mobile communication system despite electronic countermeasures has been developed. It is shown that in order to obtain high noise immunity of control and communication channels and to protect information from interception, wireless ultra-wideband communication technology should be used. This will provide large volumes and speeds of information transmission. A technical solution for the design of an ultra-wideband transceiver antenna system is proposed. Moreover, it is recommended to use the results of data processing in a fuzzy decision-making system for the transfer of service between mobile network nodes in conditions of interference. Conclusions. The scientific novelty of the obtained results is as follows. The use of ultra-wideband channels makes it possible to increase the number of control and communication channels in a wireless mobile system almost unlimitedly. The preliminary distribution of orthogonal codes between the channels realizes the process of control and communication without the interception of information and mutual interference. The use of the time-position-pulse coding method prevents the occurrence of intercharacter distortions of the encoding ultrashort pulses. This also reduces the level of distortion of information signals caused by multipath propagation, which guarantees the security of information in the system. The use of a fuzzy decision-making system for the transfer of services between mobile network nodes allows dynamically changing the network topology in real time and maintaining high quality of service under electronic countermeasures.

An efficient FPGA‐based implementation of UWB radar system for through‐wall imaging

SummaryThe work presented in this paper aims to develop a low‐cost ultra‐wideband (UWB) radar system that has the capability to image through the wall of a human target. The proposed radar system relies heavily on a field‐programmable gate array (FPGA) platform. The Xilinx FPGA Kintex‐7 (KC705) board is employed to integrate the main functionalities of the radar system, such as the generation and acquisition of a UWB signal. The generated signal is a monocycle signal, which has an ultra‐wide bandwidth. Due to the UWB nature of this signal, the radar system achieves better penetration ability, as well as high imaging resolution. However, the major challenge of a UWB radar system lies in the stage of digitization, as it requires a high sampling rate analog‐to‐digital converter (ADC). In fact, such a chip is very expensive. Hence, to reach a high sampling resolution using a low‐cost and low‐speed ADC, an efficient sampling strategy is implemented. In contrast to other UWB sampling methods, which require a hardware delay line chip, the new sampling scheme depends only on the FPGA firmware to realize a combination of real‐time and equivalent‐time sampling, which provides better jitter performance. Finally, to demonstrate the imaging capability, experimental tests are conducted in an indoor environment while human targets are located in different places. The measurement results revealed that the proposed radar system has the ability to provide 2D images that accurately determine the location of the target.

Synchronized Active Antenna Arrays for Studying the Passage of Ultra-Wideband Signals in the Atmosphere and Ionosphere

Synchronized Active Antenna Arrays for Studying the Passage of Ultra-Wideband Signals in the Atmosphere and Ionosphere

SYNCHRONIZED ACTIVE ANTENNA ARRAYS FOR STUDYING THE PASSAGE OF ULTRA-WIDEBAND SIGNALS IN THE ATMOSPHERE AND IONOSPHERE

Active synchronized antenna arrays generating ultra-wideband radiation with an electric field strength of about 1 V/m at a distance of several hundred kilometers have been studied. They are designed to study the passage of ultra-wideband signals in the surface layer of the atmosphere and through ionosphere. Synchronous antenna arrays with 4 and 9 radiating modules have been created. Their radiation has a symmetrical radiation pattern along the X and Y axes with a pulse duration at half-height of about 100 ps. They have a pulse energy potential (E × R) of about 60 and 150 kV, with a gross weight of 50 and 100 kg, respectively. Such characteristics allow these arrays to be placed on air carriers. The option of using air balloons when radiating in the surface layer of the atmosphere and the option of the meteorological rockets placing when radiating from a height of 300 km to the Earth surface is considered.

Statistical LOS/NLOS Classification for UWB Channels

Ultrawideband (UWB) technology has attracted a lot of attention for indoor and outdoor positioning systems due to its high accuracy and robustness in non-line-of-sight (NLOS) environments. However, UWB signals are affected by multipath propagation which causes errors in localization. To overcome this problem, researchers have proposed various techniques for NLOS identification and mitigation. One of the approaches is statistical LOS/NLOS classification, which uses statistical parameters of the received signal to distinguish between LOS and NLOS channels. In this paper, we formulated several techniques which can be used for effectively classifying Line of Sight (LOS) channel from a Non-Line of Sight (NLOS) channel. Various parameters obtained from Channel Impulse Response (CIR) like Skewness, Kurtosis, Root Mean Squared Delay Spread (RDS), Mean Excess Delay (MED), Energy, Energy Ratio and Mean of Covariance Matrix are used for channel classification. In addition to this, the Joint Probability Density Functions (PDFs) of various parameters are used to improve the accuracy of UWB LOS/NLOS channel classification. Two different criteria-Likelihood Ratio and Hypothesis Test are used for the identification of channel.

Survey on NLOS Identification and Error Mitigation for UWB Indoor Positioning

Ultra-wideband (UWB) positioning systems often operate in a non-line-of-sight (NLOS) environment. NLOS propagation has become the main source of ultra-wideband indoor positioning errors. As such, how to identify and correct NLOS errors has become a key problem that must be solved in high-accuracy indoor positioning technology. This paper firstly describes the influence of the NLOS propagation path on localization accuracy and the generation method of ultra-wideband signals, and secondly classifies and analyzes the currently available algorithms for ultra-wideband non-line-of-sight (NLOS) identification and error suppression. For the identification of NLOS, the residual analysis judgement method, statistical feature class identification method, machine learning method and geometric feature judgement method are discussed. For the suppression of NLOS propagation errors, weighting-based methods, filtering-based methods, line-of-sight reconstruction algorithms, neural network algorithms, optimization methods with constraints, and path tracing methods are discussed. Finally, we conclude the paper and point out the problems that need to be solved in NLOS indoor positioning.

Filtering and Detection of Ultra-Wideband Chaotic Radio Pulses with a Matched Frequency-Selective Circuit

An approach is proposed to the filtering of an additive mixture of ultra-wideband chaotic signals and white Gaussian noise, in order to retrieve the useful signal in the receiver. The role of the filter is performed by a passive frequency-selective circuit, identical to the one involved in the formation of oscillations in the chaos generator. A mathematical model of a modulating chaos generator, detecting and receiving a sequence of ultra-wideband chaotic radio pulses in a noisy channel is designed. For the receiver of sequences of symbols encoded by chaotic radio pulses with 2- and 4-position modulation, the bit error ratio as a function of the noise level and the pulse duration is estimated numerically.

Practical imaging algorithms in ultra-wideband radar systems using active aperture synthesis and stochastic probing signals

The subject of the manuscript is the algorithms for radar imaging. This research develops imaging methods and algorithms for wideband and ultrawideband active aperture synthesis systems with antenna arrays and stochastic probing signals. The use of antenna arrays makes it possible to obtain radar images without the need to move radar or antenna system in space. The use of wideband and ultra-wideband stochastic probing signals is justified by their narrow autocorrelation functions. This increased the resolution of the obtained images. The main idea of the proposed algorithms is to filter the original wideband signal into several narrowband processes. Furthermore, only the central frequencies of each narrowband signal were processed. This approach allows us to use the classical widespread methods of aperture synthesis for the case of a wideband signal. Usually, they are applicable only for narrowband signals that satisfy the condition of a quasi-monochromatic approximation. This significantly reduces the overall computational complexity of the imaging algorithm, which simplifies its further practical implementation on the existing radioelement base. Because of the simulation, a primary radar image has been obtained and the overall performance of the proposed approach to processing wideband signals has been confirmed. An increase in the quality of the obtained image when using a multiple of frequency ranges is shown. An experimental study of the effect of processing a wideband signal only at its centre frequency instead of the entire frequency band is conducted. During the experiment, the correlation functions of the signals received by two spaced receivers were obtained. As a result, the Van Cittert-Zernike theorem has been experimentally confirmed. It allows signal processing only at its centre frequency instead of the entire frequency band. Simultaneously, the prospect of expanding the bandwidth of the probing signal is indicated. It, in the presence of a wideband element base and devices for high-speed signal processing, will further increase the imaging resolution of a radar system.

Generation of optical UWB signals based on combined bright solitons

We investigate the generation of ultra-wide band (UWB) signal in all optical domain based on combined bright solitons by numerical method. The combined solitons with ultra-wideband characteristics can be obtained by multiple bright solitons. The power spectrum can be modulated by pulse interval, pulse width and phase difference of combined bright solitons to satisfy with the Federal Communications Commission (FCC) spectrum mask. Meanwhile, the transmissions of combined bright solitons in single-mode fibers are discussed. The fiber loss and dispersion effects have the influence on the transmissions of combined bright solitons. In order to eliminate dispersion effects, the stable transmission of signals in dispersion decreasing fibers is proposed.

A Compact High-Gain, High-Power, Ultrashort Pulse Signal Acquisition Device

Ultrashort pulse (USP) signal with high peak power is also called ultrawideband signal, which has a broad application prospect in radar detection and electronic countermeasures and other fields. In this paper, an acquisition device is proposed to obtain the USP signal with ultrahigh compression efficiency (CE) and ultrahigh power compression gain (PCG). The long input pulse with a time length of μs level can be compressed to a narrow pulse with a pulse width of 450 ps level (2.6–3.9 GHz) by using the proposed USP acquisition device. Under the condition without loss, the CE of the USP acquisition device can reach up to 98% according to the simulated results. In the simulation, if the material of the acquisition device is set to copper material, then the CE has some reduction due to conductor loss. In order to demonstrate the effectiveness of the proposed USP acquisition device, a USP acquisition device is established and measured. According to the measurement results, a measured PCG of 27 dB is achieved and the pulse width is approximately 460 ps. The peak power of the output USP signal reaches to 100 kW under the condition of input pulse with a power of 200 W.

Frequency and time domain characteristics of the insect visual system in optic flow

Frequency and time domain properties of the monochromatic, dichromatic, and trichromatic visual system in an insect have been studied. The research method is based on the representation of the optical flow field of the insect visual system in the form of a dynamic link with an input and output. The Gaussian function was used to approximate the spectral curves. The study of the inertial properties of such a link in the time domain was performed by applying signals to its input in the form of a δ-function or a unit function. The steady-state forced oscillations at the output of the investigated dynamic link are determined when a harmonic effect is applied to the input. A technique for constructing spectral sensitivity curves for monochrome, dichromatic, and trichromatic vision of insects in the frequency domain is proposed; it has been established that the spectra exhibit the properties of ultra wideband signals. It has been found that the dynamic link of the insect visual system is capable of amplifying the optical signal over ultraviolet and blue parts of the spectrum in the time and frequency domain. It has been revealed that at a frequency equal to or higher than the frequency of dielectric relaxation, the optical flow field of the insect's visual system does not sense electromagnetic radiation. This phenomenon is most pronounced in ultraviolet and blue parts of the spectrum. It has been established that the optical signal wideband index μ varies from 0.41 to 1.21; thus, the visual system of an insect has ultra wideband properties. It has been shown that the number of periods of light oscillations in the visual system of insects, which has a spectrum in the form of a Gaussian curve, is related to the exponent μ by a simple relationship. New knowledge gained can be used for creation of matrix solid-state photodetectors in ultraviolet and blue parts of the spectrum.

High-Resolution and Wide-Swath SAR Imaging With Sub-Band Frequency Diverse Array

High-resolution and wide-swath imaging serves as an important task for synthetic aperture radar (SAR). However, the tradeoff between high azimuth resolution and wide unambiguous swath coverage has not been well optimized in traditional SAR system. Meanwhile, the ultrawideband signal is required to obtain ultrahigh range resolution imaging. It is not easy to increase the bandwidth directly due to the difficulty of system design. To this end, this article makes notable contribution on a sub-band frequency diverse array framework to realize range ambiguous echoes separation and wideband signal synthesis from narrowband signals. By introducing a small frequency increment across the elements within each subarray, the transmit steering vector within each subarray is range-angle-dependent, making it feasible to resolve range ambiguity in the spatial frequency. In addition, the transmitted waveforms of different subarrays occupy different frequency bands in range frequency domain, which play a pivotal role in achieving high-resolution imaging. With phase compensation and sub-band frequency spectrum splicing technique, the wideband signal can be obtained. Simulation results have verified the effectiveness of the proposed approach.