Utilizing Orthogonal Coprime Signals for Improving Broadband Acoustic Doppler Current Profilers

Chi, Cheng; Vishnu, Hari; Beng, Koay Teong

doi:10.1109/joe.2019.2925922

Cited by 13 publications

(9 citation statements)

References 43 publications

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“…The common method is analyzing the echo signal or designing the transmitted signal to obtain the estimated value of integer n, such that the influence of ambiguity velocity can be eliminated. An orthogonal coprime signal is designed in [8]; the integer n can be obtained by robust CRT. C. Chi [20] proposed an unwrapping combined signal that contains three pulses y 0 , y 1 , and y 2 , where the time delay between pulses y 0 and y 1 is τ 1 , and the one between pulses y 1 and y 2 is τ 2 .…”

Section: Orthogonal Combined Signalmentioning

confidence: 99%

“…In BBADCPs, phase coding (such as Barker code, m sequence) and pulse frequency modulation are usually considered. We use phase coding in this paper; thus, a 1 (t) and a 2 (t) can be expressed as [8]:…”

Section: Orthogonal Combined Signalmentioning

confidence: 99%

“…Generally, the Doppler shift is estimated by extracting the phase of the autocorrelation function of the received complex baseband signal [8]. The pulse-pair method, also known as the covariance method, was first proposed by Miller in 1972, and has become a popular frequency estimation algorithm used in BBADCP, due to its less computation and higher accuracy [8][9][10]. S. S. Abeysekera [11] compared the pulse-pair method with Fast Fourier Transformation (FFT) and concluded that the operation of the pulse-pair method is less than that of FFT.…”

Section: Introductionmentioning

confidence: 99%

“…In recent years, N. Han [19] designed a combined signal for solving the ambiguity in current velocity measurement, discussed the design methods based on time delay and frequency, and improved the measurement accuracy. In addition, Chi Cheng [8,20] proposed an orthogonal coprime signal, which is composed of two sub-signals with different frequencies and the signal length is prime to each other. Then, the robust Chinese remainder theorem (CRT) was used to relax the limit of the ambiguity velocity of conventional BBADCPs, while the complexity also increased.…”

Section: Introductionmentioning

confidence: 99%

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Using Orthogonal Combined Signals in Broadband ADCP for Improving Velocity Measurement

Lin¹,

Yuan²,

Cheng³

2020

JMSE

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Broadband Acoustic Doppler Current Profiler (BBADCP) is a widely used technology in velocity measurements. To adapt to the varied water environment and different measurement requirements, flexible tuning of transmitted signal parameters will improve the feasibility and accuracy of velocity measurement. Compared with the conventional signal, the orthogonal combined signal designed in this paper can generate a wealth of signal combination examples and improve the accuracy of the velocity measurement under the same conditions. The proposed orthogonal combined signal consists of two orthogonal sub-signals with a symmetrical spectrum. Each is designed based on time delay to eliminate or weaken the current velocity ambiguity. Then, the processing method of the received signal when the pulse signals are the same or different coded signal is discussed. The numerical simulation results show that, when using the proposed method, the standard deviation of the estimated current velocity has different degrees of reduction at different current velocities. Our simulation also shows that, compared to the convention method, the proposed method can improve the SNR by 10 dB. This can help significantly increase the scope of the configuration.

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Section: Orthogonal Combined Signalmentioning

confidence: 99%

Section: Orthogonal Combined Signalmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Using Orthogonal Combined Signals in Broadband ADCP for Improving Velocity Measurement

Lin¹,

Yuan²,

Cheng³

2020

JMSE

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“…Regardless of the velocity ambiguity, correlation delay determines the velocity measurement range. The shorter the correlation delay, the larger the velocity measurement range; however, as the velocity measurement range increases, the sensitivity of the sonar system to the velocity change decreases, which in turn leads to a decline in the velocity estimation accuracy [16]; therefore, it is important to choose an appropriate ambiguity velocity, according to the target velocity. In some improved Doppler sonar systems, the estimated velocity of the current ping is used to dynamically adjust the ambiguity velocity of the next ping, in order to maintain optimal measurement sensitivity.…”

Section: Introductionmentioning

confidence: 99%

Improved Velocity Estimation Method for Doppler Sonar Based on Accuracy Evaluation and Selection

Yang

Fang

2021

JMSE

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The matched filtering method and the waveform-tracking method cannot maintain optimal velocity estimation performance all of the time. In order to solve this problem, this paper proposes an improved velocity estimation method for Doppler sonar, based on accuracy evaluation and selection. The echo of Doppler sonar is divided into several segments with the same width as the transmitted pulse, and each segment is regarded as the echo of the corresponding water layer. According to our study’s results, the velocity estimation accuracy of each segment is positively correlated with the ratio of its autocorrelation modulus to its power. Based on this conclusion, a velocity accuracy criterion with high accuracy and low complexity is designed in order to select the optimal velocity estimation for water layers or bottoms. The proposed accuracy selection method flexibly selects the echo interval to be processed according to the accuracy criterion, so as to maintain the optimal estimation of the current’s or bottom’s velocity. Water tank and field experiments using a prototype Doppler sonar device demonstrates that, compared with the matched filtering method and the waveform-tracking method, the average velocity estimation accuracy and bias of the proposed method are superior.

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Deep learning‐based time delay estimation for motion compensation in synthetic aperture sonars

Chen,

Chi,

Zhang

et al. 2023

IET Radar Sonar & Navi

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Accurate and robust time delay estimation is crucial for synthetic aperture sonar (SAS) imaging. A two‐step time delay estimation method based on displaced phase centre antenna (DPCA) micronavigation has been widely applied in motion estimation and compensation of SASs. However, the existing methods for time delay estimation are not sufficiently robust, which reduces the performance of SAS motion estimation. Deep learning is currently one of the cutting‐edge techniques and has brought about a remarkable progress in the field of underwater acoustic signal processing. In this study, a deep learning‐based time delay estimation method is introduced to SAS motion estimation and compensation. The subband processing is first applied to obtain ambiguous time delays between adjacent pings from phases of SAS echoes. Then, a lightweight neural network is utilised to construct phase unwrapping. The model of the employed neural network is trained with simulation data and applied to real SAS data. The results of time delay estimation and motion compensation demonstrate that the proposed neural network‐based method has much better performance than the two‐step and joint‐subband methods.

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Utilizing Orthogonal Coprime Signals for Improving Broadband Acoustic Doppler Current Profilers

Cited by 13 publications

References 43 publications

Using Orthogonal Combined Signals in Broadband ADCP for Improving Velocity Measurement

Using Orthogonal Combined Signals in Broadband ADCP for Improving Velocity Measurement

Improved Velocity Estimation Method for Doppler Sonar Based on Accuracy Evaluation and Selection

Deep learning‐based time delay estimation for motion compensation in synthetic aperture sonars

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