scholarly journals Performance of an Ultrasonic Imaging System Based on a 45-MHz Linear PVDF Transducer Array: A Numerical Study

2011 ◽  
Vol 2011 ◽  
pp. 1-15 ◽  
Author(s):  
Eivind Brodal ◽  
Frank Melandsø ◽  
Svein Jacobsen
Keyword(s):  
Acoustic Waves ◽  
Imaging System ◽  
Numerical Study ◽  
Signal To Noise Ratio ◽  
Ultrasonic Imaging ◽  
Time Derivative ◽  
Center Frequency ◽  
Transducer Array ◽  
Transducer Design ◽  
Different Depths

New designs of high-resolution ultrasonic imaging systems that operate in the 30–100 MHz region, for example, those based on linear transducer systems, are currently being investigated for medical purposes. Acoustic waves with frequencies in this range can detect microscopic structures in human tissue but will typically only penetrate a few mm because of large attenuation. However, this is sufficient for a diagnostic ultrasound scan of human skin. The signal-to-noise ratio and the focusing properties of the scanner are critical factors in dermatology, which are determined by the transducer design. A linear pulsed PVDF transducer array with a center frequency around 45 MHz is studied by applying numerical simulations, based on the finite element method (FEM), of this electromechanical system. Tx-beamforming properties of linear arrays with one, three, five, and seven active elements are investigated at different depths. The image quality obtained from synthetic Rx-beamforming, using responses from five electrodes, is estimated from reconstructed images of 25–100 m thick objects. The axial and lateral resolutions of these images are found to be similar with the Tx-beamforming resolution parameters estimated from the time-derivative of the pressure beams.

Ultrasonic Imaging System Using Spatial and Temporal M-Sequences

1979 ◽  
Vol 1 (3) ◽  
pp. 245-254 ◽  
Author(s):  
Takuso Sato ◽  
Shusou Wadaka
Keyword(s):  
Imaging System ◽  
Signal To Noise Ratio ◽  
Ultrasonic Imaging ◽  
Spatial Modulation ◽  
High Signal ◽  
Temporal Modulation ◽  
Range Resolution ◽  
M Sequence ◽  
Azimuth Resolution ◽  
M Sequences

A new ultrasonic imaging system combining temporal modulation of the ultrasonic signal by an M-sequence with spatial modulation of the wave field by a rotating M-sequence phase disk has been developed. This system uses neither beam forming nor transducer scanning, and has high resolution both in range and azimuth. The correlation function of the temporal M-sequence determines the range resolution, while the azimuth resolution is determined by the configuration of the rotating M-sequence phase disk. The use of the M-sequence modulations also results in images with high signal-to-noise ratio.

The Effect of Pulse Compression Chirp Parameters on Profilometry Information and Resolution

2018 ◽  
Author(s):  
Zuwen Sun ◽  
Natalie Baddour
Keyword(s):  
Pulse Compression ◽  
Imaging System ◽  
Matched Filter ◽  
Signal To Noise Ratio ◽  
Imaging Systems ◽  
Center Frequency ◽  
Matched Filtering ◽  
Linear Frequency ◽  
Recent Developments ◽  
Correlation Process

Recent developments in imaging systems have seen the implementation of a radar matched-filtering approach. The goal of the imaging system is to obtain information about an unknown object embedded in the system, by controlling the parameters of the input and measuring the response to the known input. The main merit of using matched filtering in imaging systems is the improvement of Signal to Noise Ratio (SNR). However, the correlation process used in matched filtering may result in a loss of resolution. One way to compensate for lost resolution is via pulse compression. Linear frequency modulated sinusoidal waveforms (chirps) have the property of pulse compression after correlation. Hence, both SNR and resolution can be enhanced by matched-filtering and pulse compression with a chirp. However, the theory behind the effect of chirp parameters on resolution is still not clear. In this paper, a one-dimensional theory of matched-filter imaging with a pulse compressed linear frequency modulated sinusoidal chirp is developed. The effect of the chirp parameters on the corresponding signal is investigated, and guidelines for choosing the chirp parameters for resolution considerations are given based on the developed theory and simulations. The results showed that by manipulating the center frequency, bandwidth, and duration of the chirp, the resolution can be easily enhanced.

An Ultrasonic Imaging System Using a Matrix-Type Transducer Array

1999 ◽  
Vol 38 (Part 1, No. 5B) ◽  
pp. 3111-3115 ◽  
Author(s):  
Michitoshi Noguchi ◽  
Koichi Mizutani ◽  
Keinosuke Nagai ◽  
Yoshinari Yamashita
Keyword(s):  
Imaging System ◽  
Ultrasonic Imaging ◽  
Transducer Array ◽  
Matrix Type ◽  
Type Transducer

Fundamental Study on Development of Air-Coupled Ultrasonic Imaging Measurement for Fuel Debris Inspection

2018 ◽  
Author(s):  
Hironobu Kiuchi ◽  
Shun Kimura ◽  
Ari Hamdani ◽  
Hideharu Takahashi ◽  
Hiroshige Kikura ◽  
...  
Keyword(s):  
Nuclear Power ◽  
Focused Ultrasound ◽  
Imaging System ◽  
Signal To Noise Ratio ◽  
Ultrasonic Imaging ◽  
Sound Field ◽  
Beam Width ◽  
Imaging Method ◽  
Fundamental Study ◽  
Control Rod

Retrieval of fuel debris is one of the most urgent issues regarding the decommissioning of Fukushima Daiichi Nuclear Power Plant (NPP). A retrieval of fuel debris requires a measurement system which can be applied in the severe environment to investigate inside the Reactor Pressure Vessel (RPV) and the Control Rod Drive (CRD) housing. In this study, an air-coupled ultrasonic measurement is proposed because of the feasibility of its application in the severe environment such as the high-radiation atmosphere. However, compared with using it in water or solids, there are some difficulties with applying the air-coupled ultrasonic technique. Therefore, we employed a point-focused transducer which can converge ultrasonic energy in a small area. As a fundamental study, this paper focuses on the experimental assessment of the potential feasibility and property of the developed air-coupled ultrasonic imaging. Firstly, to obtain the property and characteristics of the point-focused transducer, the sound field of the transducer was measured. The sound field showed the convergence rate, acoustic intensity and the beam width of the transducer. Secondly, in order to improve Signal to Noise ratio (SN ratio), the ultrasonic imaging method using a frequency correlation was designed taking the feeble ultrasonic echoes from complex shape object into consideration. Finally, the shape of a test specimen, which imitates a fuel debris, was measured with the developed imaging system. The ultrasonic image of the specimen showed a good agreement with a photo. In conclusion, the imaging using air-coupled point-focused ultrasound was developed to successfully visualize a mock fuel debris from a relatively short distance of 40 mm – 100 mm.

Some Quantification Problems in Parallel EELS Images

1990 ◽  
Vol 48 (2) ◽  
pp. 36-37
Author(s):  
G. Botton ◽  
G. L’Espérance ◽  
M.D. Ball ◽  
C.E. Gallerneault
Keyword(s):  
Electron Microscope ◽  
Imaging System ◽  
Signal To Noise Ratio ◽  
Scanning Transmission Electron Microscope ◽  
Acquisition Time ◽  
Thickness Variation ◽  
Transmission Electron ◽  
Distribution Of Elements ◽  
Scanning Transmission ◽  
Present Distribution

The recently developed parallel electron energy loss spectrometers (PEELS) have led to a significant reduction in spectrum acquisition time making EELS more useful in many applications in material science. Dwell times as short as 50 msec per spectrum with a PEELS coupled to a scanning transmission electron microscope (STEM), can make quantitative EEL images accessible. These images would present distribution of elements with the high spatial resolution inherent to EELS. The aim of this paper is to briefly investigate the effect of acquisition time per pixel on the signal to noise ratio (SNR), the effect of thickness variation and crystallography and finally the energy stability of spectra when acquired in the scanning mode during long periods of time.The configuration of the imaging system is the following: a Gatan PEELS is coupled to a CM30 (TEM/STEM) electron microscope, the control of the spectrometer and microscope is performed through a LINK AN10-85S MCA which is interfaced to a IBM RT 125 (running under AIX) via a DR11W line.

Ultrasonic Block Compressed Sensing Imaging Reconstruction Algorithm Based on Wavelet Sparse Representation

2020 ◽  
Vol 16 (3) ◽  
pp. 262-272
Author(s):  
Guangzhi Dai ◽  
Zhiyong He ◽  
Hongwei Sun
Keyword(s):  
Compressed Sensing ◽  
Sparse Representation ◽  
Linear Array ◽  
Imaging System ◽  
Ultrasonic Imaging ◽  
Large Data ◽  
Reconstruction Algorithm ◽  
Array Transducer ◽  
Total Data ◽  
Block Compressed Sensing

Background: This study is carried out targeting the problem of slow response time and performance degradation of imaging system caused by large data of medical ultrasonic imaging. In view of the advantages of CS, it is applied to medical ultrasonic imaging to solve the above problems. Objective: Under the condition of satisfying the speed of ultrasound imaging, the quality of imaging can be further improved to provide the basis for accurate medical diagnosis. Methods: According to CS theory and the characteristics of the array ultrasonic imaging system, block compressed sensing ultrasonic imaging algorithm is proposed based on wavelet sparse representation. Results: Three kinds of observation matrices have been designed on the basis of the proposed algorithm, which can be selected to reduce the number of the linear array channels and the complexity of the ultrasonic imaging system to some extent. Conclusion: The corresponding simulation program is designed, and the result shows that this algorithm can greatly reduce the total data amount required by imaging and the number of data channels required for linear array transducer to receive data. The imaging effect has been greatly improved compared with that of the spatial frequency domain sparse algorithm.

scholarly journals Multiple Narrowband Interferences Characterization, Detection and Mitigation Using Simplified Welch Algorithm and Notch Filtering

2021 ◽  
Vol 11 (3) ◽  
pp. 1331
Author(s):  
Mohammad Hossein Same ◽  
Gabriel Gleeton ◽  
Gabriel Gandubert ◽  
Preslav Ivanov ◽  
Rene Jr Landry
Keyword(s):  
Power Spectrum ◽  
Embedded System ◽  
Radio Frequency ◽  
Satellite Communication ◽  
Signal To Noise Ratio ◽  
Center Frequency ◽  
Infinite Impulse Response ◽  
Frequency Variation ◽  
Welch Method ◽  
The Embedded System

By increasing the demand for radio frequency (RF) and access of hackers and spoofers to low price hardware and software defined radios (SDR), radio frequency interference (RFI) became a more frequent and serious problem. In order to increase the security of satellite communication (Satcom) and guarantee the quality of service (QoS) of end users, it is crucial to detect the RFI in the desired bandwidth and protect the receiver with a proper mitigation mechanism. Digital narrowband signals are so sensitive into the interference and because of their special power spectrum shape, it is hard to detect and eliminate the RFI from their bandwidth. Thus, a proper detector requires a high precision and smooth estimation of input signal power spectral density (PSD). By utilizing the presented power spectrum by the simplified Welch method, this article proposes a solid and effective algorithm that can find all necessary interference parameters in the frequency domain while targeting practical implantation for the embedded system with minimum complexity. The proposed detector can detect several multi narrowband interferences and estimate their center frequency, bandwidth, power, start, and end of each interference individually. To remove multiple interferences, a chain of several infinite impulse response (IIR) notch filters with multiplexers is proposed. To minimize damage to the original signal, the bandwidth of each notch is adjusted in a way that maximizes the received signal to noise ratio (SNR) by the receiver. Multiple carrier wave interferences (MCWI) is utilized as a jamming attack to the Digital Video Broadcasting-Satellite-Second Generation (DVB-S2) receiver and performance of a new detector and mitigation system is investigated and validated in both simulation and practical tests. Based on the obtained results, the proposed detector can detect a weak power interference down to −25 dB and track a hopping frequency interference with center frequency variation speed up to 3 kHz. Bit error ratio (BER) performance shows 3 dB improvement by utilizing new adaptive mitigation scenario compared to non-adaptive one. Finally, the protected DVB-S2 can receive the data with SNR close to the normal situation while it is under the attack of the MCWI jammer.

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