Effects of fast Fourier transform window size on the target strength spectra measurements of Japanese anchovy (Engraulis japonicus) using linear frequency modulated signals

IF 2.2 2区农林科学 Q2 FISHERIES

Fisheries Research Pub Date : 2025-01-01 DOI:10.1016/j.fishres.2025.107267

Jing Liu , Tomohito Imaizumi , Kazuo Amakasu

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引用次数: 0

Abstract

The signal processing in broadband echosounders differs from that in conventional narrowband echosounders, particularly in the requirement of fast Fourier transform (FFT) with a reasonable window size (WS) to calculate accurate TS spectra from pulse-compressed echo waveforms. However, the reasonable FFT WS for the pulse-compressed echo waveforms has not been sufficiently and quantitatively investigated. This study aimed to investigate the effects of FFT WS on the TS spectra measurement of Japanese anchovy (Engraulis japonicus) through simulation and in situ experiments. First, the pulse-compressed echo waveforms of calibration spheres were simulated, then the effects of FFT WS on TS spectra measurement were investigated and compared with the results in the tank experiment. Then, the pulse-compressed echo waveforms of Japanese anchovy were simulated, the effects of FFT WS on TS spectra measurement were investigated based on the simulated echo waveforms, and finally the reasonable FFT WS of anchovy was verified with in situ data. The results demonstrated that the measured TS spectra with a narrow FFT WS of 0.05 m differed significantly from other cases (FFT WSs of 0.2, 0.4, and 0.8 m). As the FFT WS increased, the measured TS spectra became more similar and stable. Considering the exclusion of pulse-compressed echo waveforms from other targets, a 0.2-m FFT WS was deemed to be reasonable for the TS spectra measurement of Japanese anchovy.

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快速傅里叶变换窗口大小对线性调频信号测量日本凤尾鱼目标强度谱的影响

宽频带测深仪的信号处理与传统的窄带测深仪不同，特别是需要快速傅立叶变换（FFT）和合理的窗口大小（WS）来从脉冲压缩的回波波形中计算精确的TS频谱。然而，对于脉冲压缩回波波形，合理的FFT WS还没有得到充分和定量的研究。通过模拟和原位实验，研究FFT WS对日本凤尾鱼TS光谱测量的影响。首先模拟了标定球的脉冲压缩回波波形，然后研究了FFT WS对TS光谱测量的影响，并与槽内实验结果进行了比较。然后对日本凤尾鱼的脉冲压缩回波波形进行了模拟，在模拟回波波形的基础上研究了FFT WS对TS光谱测量的影响，最后用现场数据验证了凤尾鱼的合理FFT WS。结果表明，窄FFT WS为0.05 m时所测TS光谱与其他情况（FFT WS为0.2、0.4和0.8 m）差异显著。随着FFT WS的增大，测得的TS光谱变得更加相似和稳定。考虑到排除了其他目标的脉冲压缩回波波形，我们认为0.2 m FFT WS对日本凤尾鱼TS光谱测量是合理的。

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来源期刊

Fisheries Research 农林科学-渔业

CiteScore

4.50

自引率

16.70%

发文量

294

审稿时长

15 weeks

期刊介绍： This journal provides an international forum for the publication of papers in the areas of fisheries science, fishing technology, fisheries management and relevant socio-economics. The scope covers fisheries in salt, brackish and freshwater systems, and all aspects of associated ecology, environmental aspects of fisheries, and economics. Both theoretical and practical papers are acceptable, including laboratory and field experimental studies relevant to fisheries. Papers on the conservation of exploitable living resources are welcome. Review and Viewpoint articles are also published. As the specified areas inevitably impinge on and interrelate with each other, the approach of the journal is multidisciplinary, and authors are encouraged to emphasise the relevance of their own work to that of other disciplines. The journal is intended for fisheries scientists, biological oceanographers, gear technologists, economists, managers, administrators, policy makers and legislators.