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超声、雷达、多普勒成像文集

机械波的多普勒效应可以用于医学的诊断,也就是我们平常说的彩超。彩超简单的说就是高清晰度的黑白B超再加上彩色多普勒,首先说说超声的波长移诊断法,即D超,此法应用多普勒效应原理,当波源与接收体(即探头和反射体)之间有相对运动时,回波的波长有所改变,此种波长的变化称之为波长移,D超包括脉冲多普勒、连续多普勒和彩色多普勒血流图像。彩色多普勒超声一般是用自相关技术进行多普勒信号处理,把自相关技术获得的血流信号经彩色编码后实时地叠加在二维图像上,即形成彩色多普勒超声血流图像。由此可见,彩色多普勒超声(即彩超)既具有二维超声结构图像的优点,又同时提供了血流动力学的丰富信息,实际应用受到了广泛的重视和欢迎,在临床上被誉为“非创伤性血管造影”。

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超声、雷达、多普勒成像文集 文档列表

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A Low-cost Ultrasonic Rangefinder based on Frequency Modulated Continuous Wave
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:In the present work the performance of alow-cost ultrasonic rangefinder system exploiting linearchirp excitation signal and the Frequency ModulatedContinuous Wave technique is analyzed, evaluated interms of resolution and computational cost, andcompared with the results achievable by means of thestandard technique based on the matched-filter theory. The system, based on a Voltage Controlled Oscillatorand an analog mixer, shifts some of the processingrequired by the FMCW protocol in the analog domain,strongly relaxing the requirements on the signalsampling rate without reducing the achievable rangeresolution. The final target is to evaluate the possibilityof implementing the FMCW technique in very low costand hand held devices
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A Parameterized Simulation of Doppler Lidar
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:Upcoming missions to explore planetary bodies in the solar system will require accurate position and velocity data during descent in order to land safely at a predesignated site. A Doppler lidar instrument could provide measurements of the altitude, attitude, and velocity of the landing vehicle to supplement the data collected by other instruments. A flexible simulation tool would aid the tasks of designing and testing the functionality of such an instrument. LadarSIM is a robust parameterized simulation tool developed for time of flight lidar at Utah State University’s Center for Advanced Imaging Ladar. This thesis outlines how LadarSIM was modified to include a simulation of Doppler lidar. A study is performed using LadarSIM to determine the effects of varying the transmission power, aperture diameter, and fast Fourier transform (FFT) size of a Doppler lidar. Point clouds of landing scenarios generated by the simulation with different scanning patterns are shown.
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An Enhanced Chirp Modulated Golay Code for Ultrasound Diverging Wave Compounding
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:In ultrasound imaging, a straightforward way ofincreasing axial resolution is by shortening the transmittedsignals. However, short excitation provide low echo signal tonoise ratio (eSNR), which results in low image quality. Analternate solution would be to increase the excitation signal’sduration (by using binary Golay codes or chirps), and relyon off-line match filtering techniques in order to compress thereceived echoes. Resolution Enhancement Compression (REC)is a coding technique that provides better axial resolution thanconventional pulsing technique while increasing the eSNR. Itconsists on designing a pre-enhanced chirp that compensates themost attenuated frequency bands of the ultrasound probe. Theobjective of this study is to combine orthogonal binary codes withREC pre-enhanced chirps in order to boost further the eSNRprovided by REC while keeping its good performance in axial resolution. The method is applied to diverging wave compounding. Pairs of diverging waves are transmitted/received/reconstructedsimultaneously thanks to the orthogonality property of the Golaycodes. The results show that the proposed method is able to obtaina better image quality than conventional pulse imaging. Theaxial resolution and the bandwidth was improved by 38%/15%in simulation/experiment, for an excitation signal designed toprovide a 39% boost. The contrast to noise ratio and the eSNRwere improved by 3.5dB and 18.7dB respectively. Acquisitionresults suggest that the combination between binary codes andmodulated enhanced chirps can be implemented in ultrasonicimaging system.
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An Underwater Channel Model and Chirp Slope Keying Modulation Scheme Performance
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:Chirp-Slope Keying (CSK) is a new and innovative digital modulation scheme forunderwater data transmission. The underwater environment brings up severalchallenges to the manufacturing and operation of communication systems. This thesisshows through analysis and simulations the effectiveness of Chirp-Slope Keying (CSK)in providing a satisfying performance in underwater communication. The experimentconsists of modulating a chirp slope by binary numbers (representing our data). ?0? isrepresented by a linear- down chirp and ?1? is represented by a linear-up chirp . Thereceived data is first processed by a correlator receiver. Then, the detection of eitherbinary symbol is obtained by the comparison to a threshold. Simulation results fornumerous signal-to-noise ratios show that CSK provides satisfying performance forunderwater data transmission. The Mississippi gulf coast shallow water Data collected from the NationalOceanic and Atmospheric Administration (NOAA), (see appendix), allow us toaccurately generate a laboratory model for the channel of interest.
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ANALYSIS OF HUMAN ECHOLOCATION WAVEFORM FOR RADAR TARGET RECOGNITION
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:Some blind humans have developed the remarkable capability of echolocation, similar to the type used by mammals such as the bat, dolphin and whale. This population of human has shown the ability to classify targets based on their location, size, shape and material in diverse environmental conditions simply by listening to the reflected echoes of tongue clicks generated by their mouth. To date, much of the research into human echolocation has been confined exclusively to behavioral science and the analysis is inconsistent with the approaches used in engineering. The waveforms used in current radar systems appear different to those typical of mammal echolocation. It is speculated that the lack of robust success in radar target recognition may therefore be attributed to application of an inappropriate waveform. This research focuses on the analysis of human echolocation waveforms and their reflected echoes from different objects to investigate what properties of the waveform may carry target information.
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Asynchronous Chirp Slope Keying for Underwater Acoustic Communication
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:We propose an asynchronous acoustic chirp slope keying to map short bit sequenceson single or multiple bands without preamble or error correction coding on the physical layer. We introduce a symbol detection scheme in the demodulator that uses the superposed matchedfilter results of up and down chirp references to estimate the symbol timing, which removes therequirement of a preamble for symbol synchronization. Details of the implementation are disclosedand discussed, and the performance is verified in a pool measurement on laboratory scale, as wellas the simulation for a channel containing Rayleigh fading and Additive White Gaussian Noise. For time-bandwidth products (TB) of 50 in single band mode, a raw data rate of 100 bit/s is simulatedto achieve bit error rates (BER) below 0.001 for signal-to-noise ratios above ?6 dB. In dual-band mode,for TB of 25 and a data rate of 200 bit/s, the same bit error level was achieved for signal-to-noiseratios above 0 dB. The simulated packet error rates (PER) follow the general behavior of the BER, butwith a higher error probability, which increases with the length of bits in each packet.
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Bandwidth and Resolution Enhancement Through Pulse Compression
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:A novel pulse compression technique is developed that improves the axial resolution of an ultrasonicimaging system and provides a boost in the echo signal-tonoise ratio (eSNR). The new technique, called the resolution enhancement compression (REC) technique, was validated with simulations and experimental measurements. Image quality was examined in terms of three metrics: theeSNR, the bandwidth, and the axial resolution through themodulation transfer function (MTF). Simulations were conducted with a weakly-focused, single-element ultrasoundsource with a center frequency of 2.25 MHz. Experimental measurements were carried out with a single-elementtransducer (f/3) with a center frequency of 2.25 MHz from aplanar reflector and wire targets. In simulations, axial resolution of the ultrasonic imaging system was almost doubledusing the REC technique (0.29 mm) versus conventionalpulsing techniques (0.60 mm). The 3 dB pulse/echo bandwidth was more than doubled from 48% to 97%, and maximum range sidelobes were 40 dB. Experimental measurements revealed an improvement in axial resolution usingthe REC technique (0.31 mm) versus conventional pulsing(0.44 mm). The 3 dB pulse/echo bandwidth was doubledfrom 56% to 113%, and maximum range sidelobes were observed at 45 dB. In addition, a significant gain in eSNR(9 to 16.2 dB) was achie
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Bistatic and Multistatic Radar
标签:彩超多普勒成像
积分:1 类型:教程及课件上传者:太白金星上传时间:2021-08-31
简介:Bistatic and Multistatic Radar .pdf
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Blood Noise Reduction in Intravascular Ultrasound Imaging
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:Scattering from red blood cells (blood noise) increases significantly as the ultrasound frequency is increasedabove 10 MHz. This reduces the contrast between the vessel walland the lumen in intravascular ultrasound imaging which makesit difficult to localize the vessel wall and plaque. A blood noisefilter based on beam tilting and digital lateral low pass filteringis described. Beam tilting introduces a Doppler shift from bloodwhich results in a frequency separation of the vessel wall signaland the blood noise. The performance of the filter is investigatedby simulations and by in vitro experiments. The filter is found tobe effective for blood velocities exceeding approximately 50 cms1 at a 20 MHz ultrasound frequency with a beam tilt angle of10 degrees and a frame rate of 15 f.p.s. By increasing the systemfrequency to 40 MHz, increase the beam tilt angle to 15 degreesand reduce the frame rate to 10 f.p.s., the filter is effective forblood velocities below 10 cm s
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Chirp-Based FHSS Receiver with Recursive Symbol Synchronization for Underwater Acoustic Communicatio
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:In this paper, we propose a covert underwater acoustic communication method that isrobust to fading using a chirp signal combined with a frequency-hopping spread spectrum scheme. A fractional Fourier transform, which estimates the slope of the signal frequency variation, is appliedto the receiver to enable a robust and reliable symbol estimation with respect to the frequencyand irregular phase variations. In addition, since the recursive symbol synchronization can beimplemented using a chirp signal, compression and expansion effects due to the Doppler shift canbe mitigated. Simulation and lake trials were performed to verify the performance of the proposedmethod. The simulation was performed by two different methods.
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Coded Signals for High Frequency Ultrasound Imaging
标签:彩超多普勒成像
积分:1 类型:技术书籍上传者:太白金星上传时间:2021-08-31
简介:Degeneration of articular cartilage is known as a serious and painful knee diseaseseriously affecting people in all ages. The disease also marks the presence of osteoarthritiswhich is a complex musculoskeletal disorder. A successful assessment of the degenerationstatus is of great importance for estimating osteoarthritis progression, and therebybeneficial for implementing clinical treatments. Ultrasound has played a vital role inimaging the articular cartilage since it is capable of providing distinct information ofimportant cartilage structures. However, various types of noise in ultrasound signals (e.g. clutter noise) are known to limit the quality of ultrasound images, especially at highfrequencies where wave attenuation becomes severe. The possibility for improving thesignal to noise ratio (SNR) by using coded signals is therefore the motivation behind thisthesis, with the main objective is to investigate suitable codes and compression methodsfor cartilage imaging. The main focus of this thesis has been put on coded ultrasound signals and related signalprocessing methods. Transducers made from two different piezoelectric materials (PZTand PVDF) are used to image a thick cartilage sample. For each transducer, three differentwaveforms (Ricker wavelet, Gaussian chirped, and a 13-bit Barker) are used to excite theultrasonic transducers. Two different wave compression methods (Matched filtering andWiener filtering) are also explored to decode the signals received by transducers. Aheadof processing the received signals, a time calibration was used to compensate for sampletilting, yielding an improved precision in the phase/time delay. A maximum method anda center of mass method were used for calibration. The results from the experimental work show that both Chirp coded signals and Barkercoded signals work well in improving the SNR, and that both transducers are able toproduce high quality images of the cartilage sample. For the situations using codedexcitation signals, however, the PZT transducer has high requirement for excitationrepetition frequency because of its built-in delay line. Different time calibration methodshave their own applicable conditions. Matched filter and Wiener filter both perform wellfor decoding, but the “noise” parameter in the Wiener filter has to be adjusted carefullyto produce reasonable results.
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Coded Spectral Doppler Imaging from simulation to real-time processing
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:Transmission of coded pulses and matched receivefiltering can improve the ultrasound imaging penetration depthwhile preserving the axial resolution. This paper shows that thepulse compression technique may be integrated in a low-costscanner to be profitably used also in spectral Dopplerinvestigations. By operating on beamformed, demodulated anddown-sampled data in the frequency domain, a single digital signalprocessor is proved sufficient to perform both pulse compressionand (multigate) spectral Doppler algorithms in real-time. Simulations, phantom and in vivo experiments demonstrate thatthe transmission of (2.5 μs or 5μs long) linear frequency modulatedchirps with bandwidths over the range 1.6-5.4 MHz, rather thanof corresponding sine burst pulses, provide SNR improvementsvery close to theory. Even in the presence of selective tissueattenuation, SNR gains up to 11dB and 13.3dB have been obtainedfor the short and the longer chirp, respectively. This may beimportant in clinical Doppler applications where the neededpenetration depth is not achieved with sufficient SNR unless verylong bursts are transmitted.
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Coherent Processing of UpDown Linear Frequency Modulated Chirps
标签:彩超多普勒成像
积分:1 类型:技术书籍上传者:太白金星上传时间:2021-08-31
简介:A useful and popular waveform for high-performance radar systems is the Linear FrequencyModulated (LFM) chirp. The chirp may have a positive frequency slope with time (up-chirp) ora negative frequency slope with time (down-chirp). There is no inherent advantage to one withrespect to the other, except that the receiver needs to be matched to the proper waveform. However, if up-chirps and down-chirps are employed on different pulses in the same CoherentProcessing Interval (CPI), then care must be taken to maintain coherence in the rangecompressed echo signals. We present the mathematics for doing so, for both correlationprocessing and stretch processing.
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Decoupling the Doppler Ambiguity Interval from the Maximum Operational Range and Range-Resolution in
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:Classical saw-tooth Frequency Modulated Continuous Wave (FMCW) radars experience a coupling betweenthe maximum unambiguous Doppler-velocity interval, maximum operational range, range-resolution and processing gain. Operationally, a trade-off is often necessarily made betweenthese parameters. In this paper, we propose a waveform and aprocessing method that decouples the aforementioned parameterdependencies at the price of using multiple receiver channelswithin the radar. The proposed method exploits the fact that beatfrequency signals have the same baseband frequency, even if thetransmitted and received chirps occupy different radio frequencybands, and have different center-frequencies. We concatenatethose baseband signals in the time-frequency domain to restorethe range-resolution and processing gain. An overview of FMCWparameters trade-off for related waveforms and a feasibility andlimitations analysis of implementing the proposed processingmethod are presented. The method is verified by simulationsand experiments with an FMCW radar for stable, moving andextended-moving targets. We additionally have highlighted itsnon-idealities in the simulations and experiments. We found thatthe proposed method indeed alleviates the trade-off betweenFMCW operational parameters and allows the extension ofthe Doppler ambiguity interval without compromising on thoseparameters.
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Design of Orthogonal Coded Excitation for Synthetic Aperture Imaging in Ultrasound Systems
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:This paper presents a new digital front-end architecture for synthetic aperture ultrasound (SAU) imaging usingorthogonal chirps and orthogonal Golay codes. Compared toexisting systems that perform decoding before beamforming, theproposed systems have comparable performance and significantlylower computation and space complexity. Unfortunately theproposed systems suffer loss in performance in the presenceof body motion. To address this problem, we propose a simplemotion compensation scheme that improves both the SNR andthe RSLL performance. A comparison of the complexity ofboth the systems shows that while Golay code-based system haslower computation complexity than chirp-based system, if motioncompensation is included, then the complexity of the two systemsare comparable.
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DETECTION METHOD FOR WIDEBAND SHORT TIME CHIRP SIGNALS
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:Chirp signals arise in many applications of signal processing. In thispaper, we address the problem of detection of chirp signals that areencountered in a bistatic radar which we are developing for remotesensing of cosmic ray induced air showers. The received echoesfrom the air showers are wideband and characterized by very shortsweep periods. This makes our astrophysical problem a challengingone, since a very short sweep period is equivalent to a very lowenergy chirp signal. We propose a rake-like receiver which consistsof a set of filters matched to different chirp rates within a rangeof interest. We examine the detection capability of the proposedstructure through extensive numerical analysis. We also report animplementation of the proposed receiver on a National InstrumentsFlexRIO FPGA board and evaluate its performance in a laboratorysetting.
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Doppler Ultrasound - Principles and practice
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:Competent use of Doppler ultrasound techniques requires an understanding of three key components:? The capabilities and limitations of Doppler ultrasound;? The different parameters which contribute to the flow display;? Blood flow in arteries and veins. This chapter describes how these components contribute to the quality of Doppler ultrasound images. Guidelines are given on how to obtain good images in all flow imaging modes.
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Estimation and compensation of frequency sweep nonlinearity in FMCW radar
标签:彩超多普勒成像
积分:1 类型:技术书籍上传者:太白金星上传时间:2021-08-31
简介:One of the main issues limiting the range resolution of linear frequency-modulated continuous-wave(FMCW) radars is nonlinearity of frequency sweep, which results in degradation of contrast andrange resolution, especially at long ranges. Two novel, slightly different, methods to correct fornonlinearities in the frequency sweep by digital post-processing of the deramped signal wereintroduced independently by Burgos-Garcia et al. (Burgos-Garcia, Castillo et al. 2003) and Meta et al. (Meta, Hoogeboom et al. 2006). In these publications, however, no formal proof of the techniqueswas given, and no limitations were described. In this thesis, we prove that the algorithm of Meta isexact for temporally infinite chirps, and remains valid for finite chirps with large time-bandwidthproducts provided the maximum frequency component of the phase error function is sufficientlylow. It is also shown that the algorithm of Meta reduces to that of Burgos-Garcia in this limit. Adigital implementation of the method is described. We also propose a novel method to measure thesystematic phase errors which are required as input to the compensation algorithm. The applicabilityof this technique to the field of optical frequency domain reflectometry (OFDR) is noted.
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Frequency Modulated Continuous W equency Modulated Continuous Wave Radar and Video F e Radar and Vid
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:There has been a push recently to develop technology to enable the use of UAVsin GPS-denied environments. As UAVs become smaller, there is a need to reducethe number and sizes of sensor systems on board. A video camera on a UAV canserve multiple purposes. It can return imagery for processing by human users. Thehighly accurate bearing information provided by video makes it a useful tool to beincorporated into a navigation and tracking system. Radars can provide informationabout the types of objects in a scene and can operate in adverse weather conditions. The range and velocity measurements provided by the radar make it a good tool fornavigation. FMCW radar and color video were fused to perform SLAM in an outdoor environment. A radar SLAM solution provided the basis for the fusion. Correlationsbetween radar returns were used to estimate dead-reckoning parameters to obtain anestimate of the platform location. A new constraint was added in the radar detectionprocess to prevent detecting poorly observable reflectors while maintaining a largenumber of measurements on highly observable reflectors. The radar measurementswere mapped as landmarks, further improving the platform location estimates. Asimages were received from the video camera, changes in platform orientation wereestimated, further improving the platform orientation estimates. The expected locations of radar measurements, whose uncertainty was modeled as Gaussian, wereprojected onto the images and used to estimate the location of the radar reflector inthe image. The colors of the most likely reflector were saved and used to detect thereflector in subsequent images. The azimuth angles obtained from the image deteciiitions were used to improve the estimates of the landmarks in the SLAM map overprevious estimates where only the radar was used.
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Fundamental Sources of Error and Spectral Broadening in Doppler Ultrasound Signals
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:Analysis of the signals, spectra and error bounds for Doppler ultrasound signals is challenging and involves numerous concepts in signal analysis, probability, acoustics andfluid mechanics. Nonetheless, the results of this analysis must be accessible to bothengineers and clinicians who work with ultrasound technology. The engineer who designs, builds or maintains equipment must know whether specific artifacts are fundamental or can be eliminated. The clinician must be able to interpret whether specificsignal features accurately represent the flow field or result from limitations of Dopplerultrasound. This article reviews recent advances in both conceptual and numericalmodels of the Doppler ultrasound process, and relates these advances to practical aspects such as spectral broadening, velocity estimation error and data analysis error. Itthen reviews recent innovations in system implementation and signal analysis which areindicative of the future potential of Doppler ultrasound instrumentation.
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Ghost Target Identification by Analysis of the Doppler Distribution in Automotive Scenarios
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:In an automotive environment the presence of reflecting surfaces cannot beavoided. The electromagnetic wave returning from a target vehicle can get reflected onthose surfaces causing a non existing so-called ghost target. For driver assistance systems ghost targets can lead to false decisions and, therefore, they should be detected andavoided. In this paper a model for describing those ghost targets and a procedure to distinguish them from real targets using the orientation and the motion state of a vehicle ispresented.
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High-frequency Ultrasound Detection Technique with Contrast Agents
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:High-frequency ultrasound with contrast agents provides contrast enhancement for imaging,has potential for application to drug delivery, and enables local genomics research. However,high-frequency ultrasound has a significant limitation, the achievable signal-to-noise ratio (SNR)and depth of penetration. In this study, we developed a new ultrasound system that involveschirp-coded-excitation ultrasound imaging with chirped pulses as trigger signals and a cardinalfrequency of 30 MHz. A chirp is a coded signal that linearly spans a frequency bandwidth B= f2?f1, where f1 and f2 are the starting and ending frequencies, respectively. A new chirpedpulses with contrast agents to minimize the attenuation of energy in human tissues increasedthe signal-to-noise ratio (SNR) by 20 dB for high-frequency ultrasonic flow imaging of theheart of zebrafish and increased the penetration depth to 2.2 mm with pulse compression and ahandmade expander. On the other hand, in a microbubble experiment, adopting various echosignal concentrations resulted in the desired distribution of different types of microbubbles. Using the system we developed, we experimentally demonstrated that the chirp-coded excitationreduces the SNR by about 43 dB compared with unipolar and bipolar pulse excitations.
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Improving targeting of ultrasound-mediated bloodbrain barrier opening using chirp and random-based m
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:Beam distortions of focused ultrasound (FUS)caused by skull may compromise accurate targeting oftranscranial therapeutic ultrasound applications. Although, theefficacy of the random and chirp modulations in improvingtargeting have been proven in simulations, ex-vivo and inphantom studies, many other parameters that can be observed invivo are disregarded such as the heterogeneity of the soft tissue,the variability of the drug uptake and clearance among subjects. In this study, the capability of the chirp- and random-basedcoded ultrasonic excitation in improving the targeting isinvestigated using a FUS-mediated blood-brain barrier (BBB)opening protocol in mice. The coded ultrasonic excitation signalswere generated with frequency bandwidth: 1.5-1.9 MHz,pressure: 0.52 MPa, and duration: 30 s. Fifteen mice weredivided in three groups (n=5 each). One group was sonicated inthe right caudate putamen with chirp-based signal (frequencyvarying linearly), the other group was sonicated with randombased coded signal (randomly varying frequency) and they werecompared with a third group sonicated with standard monofrequency ultrasound (1.5 MHz, 0.52 MPa, burst duration: 20ms, total duration: 5 min). The mean BBB opening volumesassessed by contrast enhanced magnetic resonance imaging were9.38 ± 5.71 mm3, 8.91 ± 3.91 mm3 and 35.47 ± 5.10 mm3 for thechirp, random and standard sonication, respectively. The meancavitation levels assessed by passive cavitation detection were55.40 ± 28.43 V.s, 63.87 ± 29.97 V.s and 356.52 ± 257.15 V.s forthe same groups. The coded excitation methods improved thetargeting precision, generating lower cavitation levels and moreconfined opening volumes than the conventional sonication. Thecoded excitation methods may thus enable more precise drugdelivery and it may benefit other FUS applications that usehigher-pressure levels and require precision to ablate orstimulate the targeted region.
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Indoor Pseudo-ranging of Mobile Devices
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:In this paper, we present an indoor ultrasonic locationtracking system that can utilize off-the-shelf audio speakers(potentially already in place) to provide fine-grained indoorposition data to modern mobile devices like smartphones andtablets. We design and evaluate a communication primitivebased on rate-adaptive wide-band linear frequency modulated chirp pulses that utilizes the audio bandwidth just abovethe human hearing frequency range where mobile devicesare still sensitive. Typically transmitting data, even outsideof this range, introduces broadband human audible noises(clicks) due to the non-ideal impulse response of speakers. Unlike existing audio modulation schemes, our scheme isoptimized based on psychoacoustic properties. For example, all tones exhibit slowly changing power-levels and gradual frequency changes so as to minimize human perceivableartifacts. Chirps also bring the benefit of Pulse Compression, which greatly improves ranging resolution and makesthem resilient to both Doppler shifts as well as multi-pathpropagation that typically plague indoor environments. Thescheme also supports the decoding of multiple unique identifier packets being transmitted simultaneously. By applyinga Time-Difference-of-Arrival (TDOA) pseudo-ranging technique the mobile devices can localize themselves withouttight out-of-band synchronization with the broadcasting infrastructure. This design is not only scalable with respect tothe number of transmitters and tracked devices, but also improves user privacy since the mobile devices compute theirpositions locally. We show through user studies and experimentation on smartphones that we are able to provide submeter (95% < 10cm) accurate indoor positioning in a mannerthat is imperceptible to humans.
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Laser Chirp Linearization and Phase Noise Compensation for Frequency-modulated Continuouswave LiDAR
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:Three-dimensional (3D) sensors that measure the 3D coordinates of surfaces andobjects enable machines to observe and perceive the surroundings. They have beenwidely used in automobiles, robots, unmanned aerial vehicles, and consumer electronics. Typical 3D sensing methods include camera-based stereo vision [1] and structured light[2], radio detection and ranging (Radar) [3], ultrasonic ranging [4], and light detectionand ranging (LiDAR) [5]. Compared with other methods, LiDAR has higher resolutionsin both longitudinal and lateral directions in a long range thanks to the short wavelengthand low divergence of the laser beam. In addition, LiDAR is capable to work in darkenvironments and provide reflectivity and velocity information of the objects. A schematic of a typical LiDAR system is shown in Figure 1.1. A laser beam isemitted towards the object at a distance D via the transmitter, and the reflected orscattered light from the object is collected by the receiver and the photodetector. Thetransmitter and receiver may share the same optical aperture (monostatic configuration)or have separate apertures (bistatic configuration, as shown in Figure 1.1). To collect the3D information of the entire scene, a beam scanner may be implemented to direct thebeam towards different points on the object sequentially, or a detector array may be usedto receive the light coming back from multiple points on the object in parallel.
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Millimeter-wave Radar Point Cloud Classification and Interference Mitigation
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:Recently, millimeter-wave (mmWave) radar has been widely used in many applications, such as advanced driver-assistance systems (ADAS) on vehicles and short-rangeremote sensing (e.g., road traffic monitoring and elderly health monitoring), due toits advantages including robustness to adverse weather and illumination conditions,privacy compliance, high resolution and compact size, compared to the other sensingcounterparts. In principle, the mmWave radar can measure the range, angle andDoppler (radial velocity) of moving objects in a scene. With a chain of detection,clustering and tracking algorithms, a radar point cloud can be obtained to offer theinformation including location, velocity and trajectory of objects. However, objectclassification or recognition from its radar point cloud is a major problem that needsto be solved to meet the latest demands in those advanced applications. In this dissertation, we leverage the recent developments in deep learning to explore the solutionsof radar point cloud classification from supervised, unsupervised and semi-supervisedapproaches. Particularity, we proposed the Hybrid Variational RNN Autoencoder(HVRAE), as a generative model, to detect the elderly fall from the radar pointcloud, among other applications such as traffic monitoring and patient behavior classification. On the other hand, as the mmWave radars have increasingly been used widely, theinterference among these radars will become a severe problem in the near future. Tomitigate the radar interference, we proposed an adaptive noise canceller (ANC) basedsolution that can increase the Signal-to-Interference Ratio (SIR) of targets at a lowcost. Both the simulation and experiment show excellent SIR improvement.
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MULTIFREQUENCY ULTRASOUND RADIATION FORCE EXCITATION AND MOTION DETECTION OF HARMONICALLY VIBRATING
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:Medical imaging technology takes advantage of different physical properties to form images that have contrast related to the structure and function of many different tissues. The exploitation of new physical parameters has given rise to different imaging modalities to explore the human body. Elasticity imaging is an emerging medical imaging modality which uses tissue elasticity or stiffness as its contrast mechanism. This modality incorporates techniques from existing medical imaging techniques to obtain information about the material characteristics of internal tissues and pathological conditions.
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Optimizations for FPGA-Based Ultrasound Multiple Access Spread Spectrum Ranging
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:Indoor localization based on ultrasound signals has been carried out by several research groups. Most of the techniques rely on asingle ultrasound pulse ranging, where the Time of Flight between the ultrasound emitters and a receiver is computed. Ultrasoundorthogonal modulation techniques have also been investigated and allow to compute the range between the receiver and multiplesimultaneous emitters with increased accuracy. However, no comparative investigation on the possibilities of each of themodulation techniques, comprising Direct Sequence Spread Spectrum, Frequency Hopping Spread Spectrum, and Chirp SpreadSpectrum, could be found. Also, common optimized demodulation and correlation techniques for FPGA ready implementationsare not widely available. Moreover, the hardware requirements for capturing modulated ultrasound signals could not be foundfor all the techniques. In this work, the different modulation techniques are optimized and implemented on an FPGA. Adedicated custom ultrasound MEMS-based receiver hardware for broadband ultrasound signal capturing is developed. Severalmodulation parameters are developed and applied for optimized signal processing. The FPGA resource consumptions areevaluated for the implemented methods. All methods are compared against the regular pulse ranging method, in both singleaccess and multiple-access ranging mode. Results show that, on average, up to 8 ultrasound-modulated emitters with anorthogonal sequence of length 63 can be demodulated on a Zynq7020 FPGA. In most cases, ranging up to 8 m is demonstratedin both single- and multiple-access mode, with accuracies generally remaining at a centimeter level. The requirements andcapabilities for each of the modulation schemes are highlighted in the conclusions.
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PRINCIPLES OF DOPPLER ECHOCARDIOGRAPHY AND THE DOPPLER EXAMINATION #1
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:Doppler echocardiography is a method for detecting the direction and velocity of moving bloodwithin the heart. As will be seen in this program, the technique may be used for detection ofcardiac valvular insufficiency and stenosis as well as a large number of other abnormal flows. Thecurrent interest in Doppler echocardiography has reached a remarkable level in just the past fewyears. Doppler methods extend the use of cardiac ultrasound into the evaluation of normal andabnormal flow states and provide quantitative data that are essential in the clinical decision makingprocess concerning patients with heart disease.
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PROCESSING METHODOLOGIES FOR DOPPLER ULTRASOUND SIGNALS
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:The difference between the frequencies in Doppler systems is commonly used to determine the blood flow velocity and direction within the body, this phenomenon is known as Doppler effects. Doppler generates either continues wave (CW) or pulsed wave (PW) ultrasound. During the acquisition of Doppler data a train of pulses transmitted repeatedly to be acquired from selected region of interest. In most case Doppler signal acquisition done in more than one mode, this lead to a limitation in Doppler data acquisition. The current data acquisition in Doppler system is limited by, bioeffect of ultrasound heating, which is caused by rapid transmission of ultrasound pulses for a long time to the same location lead to increasing in the average power per unit area beyond the AIUM safety standard. Beside the complicated scanning methods when the operator used mixed mode scanning, in other words highlight a specific scan line in a B-mode image and simultaneously generate the real-time Doppler spectrogram for that line on the same display scan. In addition the current acquisition methods use too much data to acquire the image this lead in increasing the process time and limit displaying the Doppler spectrogram in real-time. To overcome this limitation we propose a framework of compressed sensing (CS) to reduce the number of acquisitions. CS is a new sampling framework; state that images and signals can be reconstructed by using a few numbers of measurements. CS is the process for acquiring and reconstructing a signal that is supposed to be sparse or compressible. CS is useful in applications where one cannot afford to collect or transmit a lot of measurements such as medical imaging, data compression and data acquisition. The result shows that the proposed data acquisition alleviates the present data acquisition limitation and successfully demonstrated in real Doppler ultrasound data.
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Processing SAR data using Range Doppler and Chirp Scaling Algorithms
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:Applications of self-illuminating remote sensing systems, and among those, Radar Imagery is growingrapidly. Unique properties of Synthetic Aperture Radar (SAR) system makes it one of the most popularand applicable methods of self illuminating remote sensing techniques for ground deformationmonitoring, seismic studies, and many photogrammetry applications. There are several methods and algorithms for processing SAR data, each are convenient for differentpurposes. Two more common and reliable algorithms are developed in this thesis: a Range DopplerAlgorithm and a Chirp Scaling Algorithm. Available software packages and toolboxes for processing SAR data such as DORIS, ROI-PAC, RAT andPULSAR have their advantage and disadvantages. Most of these packages run on Linux platform, aredifficult to use, and require quite a few pre-processing data preparations. Besides there is no general SARprocessing application that can handle all data types or suitable for all purposes. There are also softwarepackages (such as ROI-PAC) with restrictions for people from certain countries. The objective of this thesis is to process SAR data using two more common algorithms, run a comparisonbetween results of these two algorithms and to process InSAR pair images to form an Interferogram andto create a DEM. A Matlab based program is developed for this purpose with graphical user interface anda few visualization enhancement features, which facilitates processing data and producing desired output. Then, I investigate the effect of different frequency domains in the resulting image. The program I created in my thesis, has several advantages: it is open-source and very easy to modify. The program is coded in MATLAB, therefore it does not need a vast programming knowledge to be ableto customize it. You can run it on any platform that can run MATLAB 7+. At the end of this thesis, I conclude that A Range Doppler Algorithm with secondary range compressionperformed in 2D-frequency domain has a result as good as a Chirp Scaling Algorithm and has lesscomputational complexity and consumes less time. No general SAR processing algorithm could beintroduced. Most of the times algorithms need to be adjusted for particular datasets, or particularapplications. Besides, the most complicated algorithm is not always the best algorithm. For example, for apoint target detection purpose, two filtering steps in range and azimuth direction provides accurateenough result.
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Radar and Ultrasound Hybrid System for Human Computer Interaction
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:Touchless hand gesture is one emerging technologyfor human computer interaction. In this paper, we investigate thefeasibility of a hybrid system using frequency modulatedcontinuous wave (FMCW) radar and ultrasound sensors withone transmitter and one receiver to detect hand movement forcontrolling a computer. Ultrasound will be used for near rangeapplication (1 cm to 30 cm) based on range estimation. FMCWradar, on the other hand, will be used for far range application(30 cm to 120 cm) based on range, velocity, and angle of arrivalestimation. Leveraging these advantages of combining bothultrasound and FMCW radar will facilitate human hand forinteracting computer with better performance.
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Radar Measurement Fundamentals
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:Modern radar design has created complicated pulses that present significant measurement challenges. Improvements to range, resolution and immunity to interference have required phase modulated pulses, frequency chirped pulses and very narrow pulses, with many of these exhibiting high bandwidth. Tektronix provides a broad selection of test equipment suitable for radar pulses. There are instruments with specialized pulse measurements and measurement bandwidths up to 20 GHz, and signal generation equipment with radar pulse synthesis capability to near 10 GHz of bandwidth. The radar measurements discussed here are all pulse measurements. Although there are several continuous transmission types of radar, primarily doppler, the great majority of radars are pulsed. The equipment and software solutions discussed here have been optimized to provide measurement flexibility and performance. This primer addresses the needs for pulse generation and measurements, the automated measurements that are available, explanation of just how the automated measurements are made, and how pulses are generated.
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Shear wave speed and dispersion measurements using crawling wave chirps
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:This article demonstrates the measurement of shear wave speed and shear speed dispersion ofbiomaterials using a chirp signal that launches waves over a range of frequencies. A biomaterialis vibrated by two vibration sources that generate shear waves inside the medium, which isscanned by an ultrasound imaging system. Doppler processing of the acquired signal producesan image of the square of vibration amplitude that shows repetitive constructive and destructiveinterference patterns called “crawling waves.” With a chirp vibration signal, successive Dopplerframes are generated from different source frequencies. Collected frames generate a distinctivepattern which is used to calculate the shear speed and shear speed dispersion. A specialreciprocal chirp is designed such that the equi-phase lines of a motion slice image are straightlines. Detailed analysis is provided to generate a closed-form solution for calculating the shearwave speed and the dispersion. Also several phantoms and an ex vivo human liver sample arescanned and the estimation results are presented.
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Signal processing in Ultrasound Doppler and Color Flow Imaging
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:This paper reveals methods for extracting information about the velocity field from theDoppler signal. We shall restrict the analysis to time-discrete processes, and use the notation
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Signal Processing Methods for Plane-Wave Color Doppler Ultrasound Imaging
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:Conventional medical ultrasound imaging uses focused beams to scan the imaging sceneline-by-line, but recently however, plane-wave imaging, in which plane-waves are used toilluminate the entire imaging scene, has been gaining popularity due its ability to achievehigh frame rates, thus allowing the capture of fast dynamic events and producing continuousDoppler data. In most implementations, multiple low-resolution images from different planewave tilt angles are coherently averaged (compounded) to form a single high-resolutionimage, albeit with the undesirable side effect of reducing the frame rate, and attenuatingsignals with high Doppler shifts. This thesis introduces a spread-spectrum color Doppler imaging method that produces highresolution images without the use of frame compounding, thereby eliminating the tradeoffbetween beam quality, frame rate and the unaliased Doppler frequency limit. The methoduses a Doppler ensemble formed of a long random sequence of transmit tilt angles thatrandomize the phase of out-of-cell (clutter) echoes, thereby spreading the clutter power in theDoppler spectrum without compounding, while keeping the spectrum of in-cell echoes intact. The spread-spectrum method adequately suppresses out-of-cell blood echoes to achieve highspatial resolution, but spread-spectrum suppression is not adequate for wall clutter whichmay be 60 dB above blood echoes. We thus implemented a clutter filter that re-arranges theensemble samples such that they follow a linear tilt angle order, thereby compacting theclutter spectrum and spreading that of the blood Doppler signal, and allowing cluttersuppression with frequency domain filters. We later improved this filter with a redesign ofthe random sweep plan such that each tilt angle is repeated multiple times, allowing, afterensemble re-arrangement, the use of comb filters for improved clutter suppression. Experiments performed using a carotid artery phantom with constant flow demonstrate thatthe spread-spectrum method more accurately measures the parabolic flow profile of thevessel and outperforms conventional plane-wave Doppler in both contrast resolution andestimation of high flow velocities.
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Software Defined Radar
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:This paper describes the design and implementation of a software defined phased radar receiver arraydeveloped for MIT Lincoln Laboratory. This receiver array was constructed with the USRP2, aninexpensive software defined radio to allow for scalability to larger receiver arrays. The team workedclosely with Lincoln Laboratory staff to conduct time synchronization testing between the receivers inthe array in order to characterize the internal oscillator drift of the radios. The team was able to get thereceiver array synchronized within less than 2 ns. In addition to building the array, the teamimplemented radar processing algorithms in Matlab which had the ability to detect a target’s range,radial velocity and direction from the receiver with an angular resolution of 20 degrees.
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Spatial Content Understanding of Very High Resolution Synthetic Aperture Radar Images
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:Availability of large amounts of very high resolution (metric-resolution) remote sensing images from the last generation synthetic aperture radar (SAR) satellites is attracting new studies. In order to search and retrieve relevant images from large-scale databases, new techniques for automatically analyzing, interpreting and indexing SAR images are required. The methods developed for this purposes in the past were based on the understanding speckle characteristics in SAR images. The focus has been generally on the model-based textural parameter estimation in the amplitudeenvelope of SAR images, such as parametric Gibbs-based methods in the Bayesian framework. Such methods were largely successful under the assumption of stationarity of the signal in an analyzing window of convenient size on images with resolution of the order of tens of meters. The challenge we encounter in metric-resolution SAR images is the presence of a very high order of details encapsulating a non-stationarity, where model-based parameter estimation becomes inaccurate. This constraint encourages us to focus on nonparametric strategies while employing phase information to transform SAR images in a suitable space. Demonstrating the advantages and relevance of the phase information embedded in complex-valued SAR images over the use of the mere amplitudeenvelope for such strategies is an underlying contribution of this thesis. The importance of phase information is advocated with a proposed method of multiple sublook decomposition (MSLD). This method generates hyper-images from the spectral analysis of complex-valued SAR images enabling the visual exploration of targets. Subsequently, a chirplet-derived transform- the fractional Fourier transform (FrFT) has been found to be a true SAR relevant multi-scale approach, where scaling is carried out in the phase. A proposed non-parametric feature descriptor based on the use of second-kind statistical measures (logarithmic-cumulants) estimated over the amplitude-envelope of the FrFT coefficients exhibits enhanced feature space separability for improved indexing. An experimental benchmarking database is generated on single look complex (SLC) spotlight mode TerraSAR-X images for the validation of the proposed FrFT-based nonparametric technique in comparison to the existing methods. A robust methodological classification framework has been proposed for the evaluation and comparison of the studied algorithms.
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Synthetic Aperture Radar Imaging Simulated in MATLAB
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:This thesis further develops a method from ongoing thesis projects with the goalof generating images using synthetic aperture radar (SAR) simulations coded inMATLAB. The project is supervised by Dr. John Saghri and sponsored by RaytheonSpace and Airborne Systems. SAR is a type of imaging radar in which the relativemovement of the antenna with respect to the target is utilized. Through the simultaneousprocessing of the radar reflections over the movement of the antenna via the rangeDoppler algorithm (RDA), the superior resolution of a theoretical wider antenna, termedsynthetic aperture, is obtained. The long term goal of this ongoing project is to develop asimulation in which realistic SAR images can be generated and used for SAR AutomaticTarget Recognition (ATR). Current and past Master’s theses on ATR were restricted to asmall data set of Man-portable Surveillance and Target Acquisition Radar (MSTAR)images as most SAR images for military ATR are not released for public use. Also, withan in-house SAR image generation scheme the parameters of noise, target orientation, theelevation angle or look angle to the antenna from the target and other parameters can bedirectly controlled and modified to best serve ATR purposes or other applications such asthree-dimensional SAR holography.
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Synthetic Aperture Radar Synthetic Aperture Radar Land Applications Land Applications Tutorial Tutor
标签:彩超多普勒成像
积分:1 类型:教程及课件上传者:太白金星上传时间:2021-08-31
简介:The aim of this tutorial is to introduce beginners to land applications of satellite remote sensing using synthetic aperture radar (SAR). It is intended to give students a basic understanding of SAR technology, the main steps involved in the processing of SAR data, and the type of information that may be obtained from SAR images. The tutorial has three main components: I. Background and Theory – an overview of the principles behind SAR remote sensing, data processing techniques, examples of land applications, and current and future sources of SAR data. II. The Bilko Exercise – a computer practical using Bilko software with ENVISAT ASAR data, allowing students to apply the theoretical knowledge to the processing and interpretation of actual SAR data. III. Answers and Examples – model answers to questions from both parts of the tutorial. Please note that the Bilko software is designed to run efficiently on low-cost computers and demonstrate common image processing techniques in a transparent way. It is ideally suited to training and capacity building by giving beginners hands-on experience in the application of remote sensing data to a given field of research or environmental management. Bilko's strength lies in its transparency, which makes students consider the effects of different processing steps on the reliability and validity of remote sensing products. It lacks some of the advanced 'black-box' algorithms of more specialist software, and does not provide the facility for automated processing. For advanced processing of SAR data, or the processing of large volumes of data, users are advised to consider other software packages, discussed in chapter 6 of the "Background and Theory".
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Synthetic aperture ultrasound imaging
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:The paper describes the use of synthetic aperture (SA) imaging in medical ultrasound. SA imaging is a radical break with today’scommercial systems, where the image is acquired sequentially one image line at a time. This puts a strict limit on the frame rate andthe possibility of acquiring a sufficient amount of data for high precision flow estimation. These constrictions can be lifted by employingSA imaging. Here data is acquired simultaneously from all directions over a number of emissions, and the full image can be reconstructedfrom this data. The paper demonstrates the many benefits of SA imaging. Due to the complete data set, it is possible to have bothdynamic transmit and receive focusing to improve contrast and resolution. It is also possible to improve penetration depth by employingcodes during ultrasound transmission. Data sets for vector flow imaging can be acquired using short imaging sequences, whereby boththe correct velocity magnitude and angle can be estimated. A number of examples of both phantom and in vivo SA images will be presented measured by the experimental ultrasound scanner RASMUS to demonstrate the many benefits of SA imaging. 2006 Elsevier B.V. All rights reserved.
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Telescope Array Radar (TARA) Observatory for Ultra-High Energy Cosmic Rays
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:Construction was completed during summer 2013 on the Telescope Array RAdar (TARA) bi-static radar observatoryfor Ultra-High-Energy Cosmic Rays (UHECR). TARA is co-located with the Telescope Array, the largest “conventional” cosmic ray detector in the Northern Hemisphere, in radio-quiet Western Utah. TARA employs an 8 MWEffective Radiated Power (ERP) VHF transmitter and smart receiver system based on a 250 MS/s data acquisitionsystem in an effort to detect the scatter of sounding radiation by UHECR-induced atmospheric ionization. TARAseeks to demonstrate bi-static radar as a useful new remote sensing technique for UHECRs. In this report, we describethe design and performance of the TARA transmitter and receiver systems.
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Theory and Application of Motion Compensation for LFM-CW SAR
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:Small low-cost high-resolution synthetic apertureradar (SAR) systems are made possible by using a linearfrequency-modulated continuous-wave (LFM-CW) signal. SARprocessing assumes that the sensor is moving in a straight line at aconstant speed, but in actuality, an unmanned aerial vehicle (UAV)or airplane will often significantly deviate from this ideal. Thisnonideal motion can seriously degrade the SAR image quality. Ina continuous-wave system, this motion happens during the radarpulse, which means that existing motion compensation techniquesthat approximate the position as constant over a pulse are limitedfor LFM-CW SAR. Small aircraft and UAVs are particularlysusceptible to atmospheric turbulence, making the need for motioncompensation even greater for SARs operating on these platforms. In this paper, the LFM-CW SAR signal model is presented, andprocessing algorithms are discussed. The effects of nonideal motion on the SAR signal are derived, and new methods for motioncorrection are developed, which correct for motion during thepulse. These new motion correction algorithms are verified withsimulated data and with actual data collected using the BrighamYoung University μSAR system.
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TOWARD ORBITAL SEISMOLOGY THEORY FOR SPECKLE NOISE REDUCTION IN LASER DOPPLER VIBROMETER MEASUREMENT
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:The interior structures of small planetary bodies such as asteroids and comets are anenigma, yet understanding them has immense value. Knowing the internal structure is important for understanding the formation and evolution of the solar system and also hasimplications for in-situ resource exploitation and planetary defense from asteroids. Despitethe immense value, no detailed investigation of the interior properties of an asteroid has yetbeen made. Although orbital radar and lander based seismological approaches have beenproposed to make direct interior observations, it has not yet been demonstrated that radarcould transmit through a rocky asteroid, nor that landing multiple seismometers is feasible or affordable. An elegant alternative to landed seismometers is orbital laser Dopplervibrometry, which could record seismic shaking of a small body without contact with thesurface. Laser Doppler vibrometers (LDVs) are mature instruments for terrestrial applications; and could function similarly in a space environment. However, when incident on arough surface like an asteroid regolith, an LDV is subject to laser speckle noise which maybe misinterpreted as seismic shaking. I address the challenge of making LDV measurementson naturally rough surfaces by quantifying the laser speckle noise that an orbital LDV wouldencounter during a hypothetical orbital measurement. Specifically, I simulate an LDV measurement of a seismic signal generated by an impact source on the asteroid 101955 Bennu. I demonstrate that speckle noise can be attenuated by combining multiple signals recordedby an orbital seismometer equipped with multiple LDV sensors. By mitigating laser speckle,I demonstrate that an orbital LDV can record seismic signals on a natural asteroid surface,which would enable an orbital seismometer to achieve the dense global coverage necessaryfor high resolution interior imaging.
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Ultrasound and FMCW Radar Hybrid System for Human Computer Interaction
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:Touchless hand gesture is an emerging technology for human computerinteraction. This thesis investigates the feasibility of a hybrid system using frequencymodulated continuous wave (FMCW) radar and ultrasound sensors to detect varioushand movement for controlling a computer. Ultrasound will be used for near-rangeapplication (1 cm to 30 cm) based on range estimation. FMCW radar, on the otherhand, will be used for far-range application (30 cm to 120 cm) based on range,velocity, and angle of arrival estimation. A noise removal algorithm and a range gatingalgorithm to separate human hand and human body will also be introduced in thisthesis. Leveraging the advantages of combining both ultrasound and FMCW radar willfacilitate human hand to interact computer with better performance. These detectedhand gestures will be applied to remote control of computers or smart TVs at adistance from 0 cm to 120 cm.
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Ultrasound Imaging Using Coded Signals
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:Modulated (or coded) excitation signals can potentially improve the quality and increase the framerate in medical ultrasound scanners. The aim of this dissertation is to investigate systematicallythe applicability of modulated signals in medical ultrasound imaging and to suggest appropriatemethods for coded imaging, with the goal of making better anatomic and flow images and threedimensional images. On the first stage, it investigates techniques for doing high-resolution codedimaging with improved signal-to-noise ratio compared to conventional imaging. Subsequently itinvestigates how coded excitation can be used for increasing the frame rate. The work includes bothsimulated results using Field II, and experimental results based on measurements on phantoms aswell as clinical images. Initially a mathematical foundation of signal modulation is given. Pulse compression based onmatched filtering is discussed. Correlation and compression properties of coded signals are shownto depend on a single parameter of the coded signals: the time-bandwidth product. It is shown that,due to attenuation in the tissues, the matched flter output is related to the ambiguity function of theexcitation signal. Although a gain in signal-to-noise ratio of about 20 dB is theoretically possiblefor the time-bandwidth product available in ultrasound, it is shown that the effects of transducerweighting and tissue attenuation reduce the maximum gain at 10 dB for robust compression withlow sidelobes. Frequency modulation and phase modulation are considered separately and their resolution, sidelobes, expected signal-to-noise gain and performance in tissue imaging are discussed in detail. Amethod to achieve low compression sidelobes by reducing the ripples of the amplitude spectrumof the FM signals is described.
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Ultrasound Imaging
标签:彩超多普勒成像
积分:1 类型:教程及课件上传者:太白金星上传时间:2021-08-31
简介:Introduction – conventional ultrasonography  Images are acquired in reflection, or pulse-echo, mode  An array of small piezoelectric elements transmits a focused pulse along a specified line of sight known as a scan line  Echoes returning from the tissue are received by the same array • focused via the delay-and-sum beamforming process • demodulated to obtain the magnitude, or envelope, of the echo signal
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Use of Chirps in Medical Ultrasound Imaging
标签:彩超多普勒成像
积分:1 类型:技术书籍上传者:太白金星上传时间:2021-08-31
简介:A “chirp” is a frequency modulated signal widely used in ultrasound imaging to increase the signal-to-noise ratio and penetration depth. In medicalultrasound imaging, resolution and penetration are two major criteria thatare inversely proportional. Because of this inverse relation, short durationpulses cannot achieve a high resolution with good penetration. The reasons for this trade-off are the decrease in signal energy due to shorter pulseduration and the attenuation in tissue, which increases with the excitation frequency. The chirp coded excitation however can increase the totaltransmitted energy using longer pulse durations, while the resolution canbe recovered by decoding on receive. Therefore, chirp signals offer potentialadvantages over single carrier short duration pulses for medical imaging. This work addresses the possible problems encountered in medical ultrasound imaging with chirps and offers new solutions to these problems interms of signal processing. These proposed solutions are then applied tothree major categories of medical ultrasound imaging; hard-tissue ultrasound imaging, soft-tissue ultrasound imaging and contrast-enhanced ultrasound imaging. The application of coded excitation in medical ultrasound imaging is themain motivation behind this work. Therefore, the concepts of frequencymodulation and matched filtering are introduced first, and ultrasound specific problems for pulse compression of chirps are discussed. Examples aregiven on specific applications and circumstances, where the performance ofthe traditional pulse compression techniques drops significantly
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Using EMD-FrFT Filtering to Mitigate Very High Power Interference in Chirp Tracking Radars
标签:彩超多普勒成像
积分:1 类型:学术论文上传者:太白金星上传时间:2021-08-31
简介:This letter presents a new signal processing subsystem for conventional monopulse tracking radars that offersan improved solution to the problem of dealing with manmadehigh power interference (jamming). It is based on the hybrid useof empirical mode decomposition (EMD) and fractional Fouriertransform (FrFT). EMD-FrFT filtering is carried out for complexnoisy radar chirp signals to decrease the signal’s noisy components. An improvement in the signal-to-noise ratio (SNR) of upto 18 dB for different target SNRs is achieved using the proposedEMD-FrFT algorithm.

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