Echo Interference Research Articles

A signal processing method for continuous mud pressure wave signals in logging-while-drilling systems

For signal transmission of mud pressure waves in logging-while-drilling systems, as more measurement parameters are adopted, the conventional signal transmission rate of approximately 1 bps cannot meet the requirements of parameter uploading. Transmission rates greater than 10 bps are widely used by current Chinese and international enterprises in their continuous wave transmission systems. Due to the increasing transmission rates, a conventional single-channel pressure sensor cannot effectively identify the key features of an original signal with a low signal-to-noise ratio at a high transmission rate. This issue results in a low success rate for pressure wave recognition and decoding. This paper addresses a method for the collection of pressure wave signals using multi-channel pressure sensors through the analysis of the signal transmission changes of mud pressure waves with well depths and echo interference caused by drilling rod reflection. In this research, numerical simulation and experimental verification were used to calculate the cross-correlations of the multi-channel signals to effectively remove interference noises such as reflective waves and improve the signal-to-noise ratio of the original signal. The results showed that this method could effectively improve the SNR after the wave filtering of the original pressure wave. The characteristics of the continuous mud pressure wave signals were analysed using a circulation test. A corresponding band-pass filter was designed to remove pump noises to restore the sinusoidal pressure wave signal required by the original transmission rules.

Digital Communication through Solids Using Magnetostriction

Digital communication through solid materials such as metals, ceramics, organic solids, or semiconductors has many applications. Only communication through metals has been attempted via ultrasonic waves. However, its performance is significantly hindered by echo interference. A way to enable communication through these solids is by the exploitation of magnetostriction. Magnetostriction is a property where a magnetic material changes its shape during the process of magnetization, essentially converting magnetic energy into kinetic energy. The kinetic energy produced by the magnetic material can then be taken through the solid media through which communication is intended to occur. The kinetic signal on the other side of the solid media could be converted to whatever type of energy is suitable for the application.This energy transduction channel, using magnetic energy and kinetic energy, can optimally be achieved through a soft magnetic material with high magnetostriction. A nickel-iron-cobalt based alloy was used to develop a material with a saturation magnetostriction over 200ppm, that can be electrodeposited out of an acidic aqueous chemistry. Initial high intrinsic stress in the deposited alloy was controlled with additives and altering the complexing, enabling consistent deposits of over a millimeter in thickness.The electrodeposited material’s performance is characterized and correlated to material properties such as alloy composition, microstructure, grain size, coercivity, magnetic saturation, Young’s Modulus, etc. The characterization methods used to analyze the magnetostrictive material and the effect of modulating plating parameters to control material properties will be presented. Additionally, the effect of annealing the material in an inert environment at varying temperatures and dwell times will be examined. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the U.S. Department of Energy or the United States Government. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525

Feedback-Based Beam Training for Intelligent Reflecting Surface Aided mmWave Integrated Sensing and Communication

The intelligent reflecting surface (IRS) aided integrated sensing and communication (ISAC) is a promising technique in mmWave systems. However, most of the existing works on IRS-aided ISAC assume the availability of channel state information (CSI) along with high-overhead channel estimation. Besides, none has taken the impact of the echo interference from the communication user on the practical sensing performance into account. In this paper, we focus on the beamforming design in the presence of the destructive interference echo signal from the communication user and accordingly formulate a beam training problem for enhancing both sensing and communication performances. Considering that no CSI is available at the base station (BS), we propose a feedback-based joint active and passive beam training scheme by invoking a modified particle swarm optimization (PSO) method without requiring high-overhead cascaded channel estimation. Specifically, the BS updates the active and passive beams based on its received echo signal and user feedback information in the beam training period and then assigns them for more accurate sensing and more efficient communication in the ISAC period. Simulation results demonstrate the advantages of the proposed feedback-based beam training scheme over the conventional beamforming schemes without considering the interference echo signal, in terms of both sensing and communication performances. Moreover, it is shown that the destructive echo interference from the communication user can be effectively mitigated by limiting the communication signal-to-noise ratio, thereby achieving better sensing performance.

Integrated Communication and Positioning With Resonant Beam

The demands for integrated communication and positioning (ICP) have been put forward in Internet of Things. However, the existing ICP systems either face challenges in trade-off between data rates and positioning accuracy or have difficulties in guaranteeing human safety while maintaining excellent performance. In this paper, we propose a monocular resonant beam-based ICP (RB-ICP) design for simultaneously realizing high-rate data transfer and high-accuracy localization while keeping the features as intrinsic safety. Utilizing the high-efficiency transmission channel of resonant beam system and the frequency-doubled beam design, we introduce the communication model without the echo interference issue. Then, we propose a distance estimation model using the phase-shift method with frequency-quadrupled beam design. Next, the angle of arrival estimation can be conducted relying on the energy-concentrated and self-alignment features of resonant beam. The simulation methods including centroid algorithm and signal conversion simulation in a photosensor along with the noise analysis are presented. In numerical analysis, we demonstrate that the positioning error can be less than 1cm and the achievable spectral efficiency can reach 16bit/s/Hz over 2m distance in 15° field of view (FoV). This proposed system enables simultaneous high-rate data transfer and high-accuracy receiver positioning for the applications such as augmented reality/virtual reality (AR/VR).

Satellite laser ranging at ultra-high PRF of hundreds of kilohertz all day

Satellite laser ranging (SLR) had been operated at a pulse repetition frequency (PRF) from ∼10 Hz to 10 kHz; the ultra-high PRF of SLR (UH-SLR) is a trend of development. In this study, an alternate working mode of laser firing and gated pulse bursts is proposed to solve the problem of laser echo interference by laser backscattering. Through an ultra-high PRF of 200-kHz picosecond green laser with single-pulse energy of 80 μJ and a pulse width of 10 ps and a ranging gate device, UH-SLR has been built by an aperture of the 60-cm SLR system in the Shanghai Astronomical Observatory. By this UH-SLR, low-orbit to high-orbit and geostationary orbit satellites are measured night and day and also for low-orbit and medium-orbit satellites in the daytime. The normal point (NP) accuracy is ∼30 μm for low-orbit satellites and ∼100 μm for high-orbit satellites, which provides an effective method for the development of ultra-high PRF and high-precision space target laser ranging.

A Quality Control Method and Implementation Process of Wind Profiler Radar Data

Wind profiler radar (WPR) is used for all-weather atmospheric wind-field monitoring. However, the reliability of these observations reduces significantly when there is electromagnetic interference echo, generally caused by ground objects, birds, or rain. Therefore, to optimize the data reliability of WPR, we proposed a synthetic data quality control process. The process included the application of a minimum connection method, judgment rule, and median test optimization algorithm for optimizing clutter suppression, spectral peak symmetry detection, and radial speed, respectively. We collected the base data from a radiosonde and multiple radars and conducted an experiment using these data and algorithms. The results indicated that the quality control method: (1) had good adaptability to multiple WPRs both in clear sky and precipitation; (2) was useful for suppressing ground clutter and (3) was superior to those of the manufacturer as a whole. Thus, the data quality control method proposed in this study can improve the accuracy and reliability of WPR products and multiple types of WPR, even when they function under vastly different weather conditions.

Mobile Optical Communications Using Second Harmonic of Intra-Cavity Laser

Optical wireless communication (OWC) meets the demands of the future six-generation mobile network (6G) as it operates at several hundreds of Terahertz and has the potential to enable data rate in the order of Tbps. However, most beam-steering OWC technologies require high-accuracy positioning and high-speed control. Resonant beam communication (RBCom), as one kind of non-positioning OWC technologies, has been proposed for high-rate mobile communications. The mobility of RBCom relies on its self-alignment characteristic where no positioning is required. In a previous study, an external-cavity second-harmonic-generation (SHG) RBCom system has been proposed for eliminating the echo interference inside the resonator. However, its energy conversion efficiency and complexity are of concern. In this paper, we propose an intra-cavity SHG RBCom system to simplify the system design and improve the energy conversion efficiency. We elaborate the system structure and establish an analytical model. Numerical results show that the energy consumption of the proposed intra-cavity design is reduced to reach the same level of channel capacity at the receiver compared with the external-cavity one.

Experimental study on the damage monitoring of a Pi-type pipeline based on ultrasonic guided waves

Aiming at the damage of the prefabricated counter bore at the elbow of the scribble pressure pipeline, a test system is established based on the ultrasonic guided wave technology, and the end echo interference is eliminated by arranging a multi-channel sensor array to achieve accurate positioning of the pipeline damage and return the measured damage Comparing the wave amplitude value with the 3% DAC curve to calculate the pipe damage cross-sectional loss rate, the test results show that the average relative error between the monitored damage cross-sectional loss rate and the actual cross-sectional loss rate is 3.46%, and the average relative error of damage location is 2.05%.

Damage Identification of Pipeline Based on Ultrasonic Guided Wave and Wavelet Denoising

Guided wave technology shows excellent capacity in the damage identification of the pipeline. In practical inspection, the detection ability is greatly reduced due to the interference echo signal from the feature structure in the pipeline. In this paper, the propagation models of guided wave in straight pipe and pipe with feature structures are established, and the effect of feature structure on the guided wave echo signal is analyzed, including pipe with an elbow, ring joint, and accessory structure, and the corresponding damage identification strategies for pipe with different forms of features are proposed. The damage index of the echo signal difference and radial displacement signal is proposed to extract the signal from damage. Besides, to eliminate the noise effect caused by the actual detection situation, a novel guided wave denoising method based on the wavelet analysis is studied, and the analysis results indicate that the damage detection strategy based on the guided wave can accurately locate the damage region in both straight pipe and pipe with features and that the proposed denoising method can effectively eliminate the noise in the echo signal.

Retro-Reflective Beam Communications With Spatially Separated Laser Resonator

Optical wireless communications (OWC) utilizing infrared or visible light as the carrier attracts great attention in 6G research. Resonant beam communications (RBCom) is an OWC technology which simultaneously satisfies the needs of non-mechanical mobility and high signal-to-noise ratio~(SNR). It has the self-alignment feature and therefore avoids positioning and pointing operations. However, RBCom undergoes echo interference. Here we propose an echo-interference-free RBCom system design based on second harmonic generation. The transmitter and the receiver constitute a spatially separated laser resonator, in which the retro-reflective resonant beam is formed and tracks the receiver automatically. This structure provides the channel with adaptive capability in beamforming and alignment, which is similar to the concept of intelligent reflecting surface (IRS) enhanced communications, but without hardware and software controllers. Besides, we establish an analytical model to evaluate the beam radius, the beam power, and the channel capacity. The results show that our system achieves longer distance and smaller beam diameter for the transmission beyond 10 Gbit/s, compared with the existing OWC technologies.

Method for acquiring time of flight from high aliasing signal in heat exchange fouling ultrasonic testing

In heat exchange fouling ultrasonic testing, the time-domain signal waveform often contains high aliasing due to small fouling thickness or high order echo interference, and so forth. This paper studies the method of acquiring time of flight from heat exchange fouling ultrasonic testing signal with high aliasing and presents the method that combined the Wiener deconvolution and high order cumulative spectrum estimation. For reference signal distortion problem, which may exist in real application, an iterative correction process is introduced in the form of Incremental Wiener algorithm. Simulation and experimental results show that the proposed method has better anti-noise ability, better time of flight accuracy and practicability.

3D Virtual Animation Instant Network Communication System Design

This project uses Openfire to implement a virtual 3D animation instant messaging system, which is easier to use and more expandable. The main work of the client is to implement the Extensible Messaging and Presence Protocol (XMPP) and use XMPP to transmit data to the server side and receive data from the server side, while Openfire is built by the server side to use. To address the problem that the current mainstream face key point localization model is less robust to complex environments, this project adopts a deep learning‐based approach to design and implement the face key point localization model, through data preprocessing, model design, and model training, to achieve a robust model that can locate 68 face key points and complete the migration of the model to mobile. The current video communication often suffers from delay and lag, so this project uses face key point data instead of video stream data transmission to reduce the pressure on the network. This topic also uses voice coding and decoding, noise reduction, echo cancellation, and other processing to solve the problems of noise interference and echo interference in voice transmission. This paper also introduces the creation, import, and loading of 3D virtual models, and explains how to use face key point association to drive 3D animation models, how to make the drive smoother and more natural, and using individual face key points as an example.

Resonant Beam Communications With Echo Interference Elimination

Resonant beam communications (RBCom) is capable of providing wide bandwidth when using light as the carrier. Besides, the RBCom system possesses the characteristics of mobility, high signal-to-noise ratio (SNR), and multiplexing. Nevertheless, the channel of the RBCom system is distinct from other light communication technologies due to the echo interference issue. In this paper, we reveal the mechanism of the echo interference and propose the method to eliminate the interference. Moreover, we present an exemplary design based on frequency shifting and optical filtering, along with its mathematic model and performance analysis. The numerical evaluation shows that the channel capacity is greater than 15 bit/s/Hz.

Effect of an echo sequence to a trapped single-atom interferometer with photon momentum kicks.

We investigate a single-atom interferometer (SAI) in an optical dipole trap (ODT) with photon momentum kicks. An echo sequence is used for the SAI. We find experimentally that interference visibilities of a counter-propagating Raman type SAI decay much faster than the co-propagating case. To understand the underlying mechanism, a wave-packet propagating simulation is developed for the ODT-guided SAI. We show that in state dependent dipole potentials, the coupling between external dynamics and internal states makes the atom evolve in different paths during the interfering process. The acquired momentum from counter-propagating Raman pulses forces the external motional wave packets of two paths be completely separated and the interferometer visibility decays quickly compared to that of the co-propagating Raman pulses process. Meanwhile, the echo interference visibility experiences revival or instantaneous collapse which depends on the π pulse adding time at approximate integer multiples or half integer multiples of the trap period.

Application of Beamforming Technology in Ionospheric Oblique Backscatter Sounding with a Miniaturized L-Array

In this paper, a new dedicated multi-channel ionospheric oblique backscatter sounder is described. A miniaturized L-shaped antenna array was employed for the receiving of the oblique backscatter echoes in the present system. Firstly, two typical adaptive beamforming algorithms were introduced to improve the anti-jamming ability. Then, simulations were carried out to verify the beamforming performance in azimuth and elevation simultaneously. Furthermore, the experimental results by the present sounding system were used to test the performance of the adaptive beamformers. Results show that the radio frequency interference and the interference of the vertical echoes can be effectively suppressed by the adaptive beamformers. In particular, the use value of the beamforming in the receiving of the ionospheric oblique backscatter sounding is described in detail through the analysis of the signal sequences in several typical frequencies. And after the constant false-alarm rate processing, the oblique backscatter ionograms processed by the adaptive beamforers have clearer and continuous leading edge compared with the original ionograms. As a result, the adaptive beamformers of great significance to improve the detection ability of the ionospheric oblique backscatter sounding.

Resonant Beam Communications: Principles and Designs

Wireless optical communications (WOC) has carriers up to several hundred terahertz, which offers several advantages, such as ultrawide bandwidth and no electromagnetic interference. Conventional WOC that uses light transmitters such as light emitting diodes (LEDs), directed LEDs, and lasers are facing major challenges in attenuation or tracking. Resonant beam communications (RBCom) meets the requirements of low attenuation, non-mechanical mobility, and multiple access. Yet, RBCom channel undergoes echo interference in contrast to common non-echo channels. An interference elimination method based on optical filtering is presented along with an exemplary interference-free RBCom system.

Automated Algorithm for Accurate Doppler Profile Detection of MST Radar Signals Considering Removal of Interference

Identifying the accurate radar echo returns from the MST (Mesosphere-Stratosphere–Troposphere) region poses serious challenges, as the radar echo signals are of very low amplitude and hidden in noise. The process of extraction of the relevant signal information becomes intricate when the spectra sometimes are infected with interference signals of non-atmospheric origin. An automated algorithm is suggested for eliminating the interference bands in the Doppler spectra of MST radar signals. The process of removal of interference and de-noising of the radar echoes using soft thresholding techniques was achieved simultaneously. The algorithm was practically applied to interference contaminated MST radar data taken from National Atmospheric Research Laboratory (NARL), Gadanki, Tirupati and studied for removal of interference bands. It was found that the projected algorithm effectively removes multiple interference bands and also improves signal detectability. The power and Doppler values (moments) are estimated using FFT and HHT (Hilbert Huang Transform) and median Doppler is plotted on Doppler power spectrum and compared.

Generating cognitive maps using echo features from a biomimetic audible sonar.

A sonar cognitive map displays target components that are specified by signal features extracted from a single binaural echo pair. A biomimetic audible sonar probes targets configured using posts connected by tangential planes. Echo envelopes are processed to extract values of eight parameters that govern the mapping process. Being tuned to recognize posts and planes, a cognitive map is composed of these two components using the posts' centers and radii as landmarks. A platform with translational and rotational degrees of freedom implements a landmark-centric scanning trajectory whose step size adaptively changes with echo information. The sonar tracks the target surface by maintaining a constant first-echo arrival time and by equalizing binaural echo times to form singular echoes that identify landmarks. The mapping process employs five states from detection to termination that pass through the singular echo state. Separate states process echo interference caused by two posts and echoes from planar surfaces. Sonar scanning stops when the current landmark parameters match those of the first landmark. Two targets configured with three posts and an added plane illustrate the procedure. Cognitive maps exhibit landmark locations that are accurate to ±5% with post radius estimates accurate to ±20%.

Ultrasound navigation based on minimally designed vehicle inspired by the bio-sonar strategy of bats

ABSTRACTIn this study, we conducted vehicle experiments and a numerical simulation based on a simple algorithm inspired by the bio-sonar system of bats to investigate how the behavioral strategy employed by bats contributes to acoustic navigation for minimal-design sensing. In particular, a double-pulse scanning method inspired from the echolocation behavior of bats was proposed, in which (1) the direction of ultrasound emission by a vehicle equipped with 1 transmitter and 2 receivers was alternately shifted between the movement direction of the vehicle and the direction of the nearest obstacle, and (2) the movement direction of the vehicle was calculated for every double-pulse emission based on integrated information from all echoes detected. As a result of 100 repeated drives in a practical course, the success rate of an obstacle-avoidance drive improved from 13% with the conventional single-pulse scanning method to 73% with the proposed method. Furthermore, the numerical simulation demonstrated that the proposed method achieves robust path planning by suppressing the localization ambiguity due to the interference of multiple echoes. The practical experiments and numerical simulation suggest that bats employ a simple behavioral solution in the operation of acoustic sensing for various problems occurring in the real world.

Forming maps of targets having multiple reflectors with a biomimetic audible sonar.

A biomimetic audible sonar mimics human echolocation by emitting clicks and sensing echoes binaurally to investigate the limitations in acoustic mapping of 2.5 dimensional targets. A monaural sonar that provides only echo time-of-flight values produces biased maps that lie outside the target surfaces. Reflector bearing estimates derived from the first echoes detected by a binaural sonar are employed to form unbiased maps. Multiple echoes from a target introduce phantom-reflector artifacts into its map because later echoes are produced by reflectors at bearings different from those determined from the first echoes. In addition, overlapping echoes interfere to produce bearing errors. Addressing the causes of these bearing errors motivates a processing approach that employs template matching to extract valid echoes. Interfering echoes can mimic a valid echo and also form PR artifacts. These artifacts are eliminated by recognizing the bearing fluctuations that characterize echo interference. Removing PR artifacts produces a map that resembles the physical target shape to within the resolution capabilities of the sonar. The remaining differences between the target shape and the final map are void artifacts caused by invalid or missing echoes.