The Experts below are selected from a list of 24402 Experts worldwide ranked by ideXlab platform
Binbin Cheng - One of the best experts on this subject based on the ideXlab platform.
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A Side-Lobe Suppression Method Based on Coherence Factor for Terahertz Array Imaging
IEEE Access, 2018Co-Authors: Yanwen Jiang, Hongqiang Wang, Bin Deng, Binbin ChengAbstract:Terahertz (THz) arrays can be used to improve the data acquisition speed conSiderably in realtime imaging applications. However, the THz array imaging usually suffers from the Side-Lobe artifacts, which leads to a severe decline in the image quality. In this paper, a Side-Lobe suppression method based on coherence factor is proposed to improve the image quality. The influences of signal-to-noise ratio on the imaging results are analyzed by simulation. Furthermore, the results based on the real-world data validate the effectiveness of the proposed method, which indicates that the Side-Lobe is suppressed by 29 dB. This paper can benefit the development of THz imaging technique and its applications in real-time imaging realms.
Tie Jun Cui - One of the best experts on this subject based on the ideXlab platform.
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Suppressing Side-Lobe Radiations of Horn Antenna by Loading Metamaterial Lens
Scientific Reports, 2015Co-Authors: Mei Qing Qi, Bai Cao Pan, Yong Zhi Sun, Hui Feng Ma, Zui Tao, Wen Xuan Tang, Tie Jun CuiAbstract:We propose a new approach to control the amplitude and phase distributions of electromagnetic fields over the aperture of a horn antenna. By loading a metamaterial lens inSide the horn antenna, a tapered amplitude distribution of the aperture field is achieved, which can suppress the Side-Lobe radiations of the antenna. The metamaterial is further manipulated to achieve a flat phase distribution on the horn aperture to avoid the gain reduction that usually suffers in the conventional low-SideLobe antenna designs. A prototype of the metamaterial-loaded horn antenna is designed and fabricated. Both numerical simulations and measured results demonstrate the tapered aperture-field distribution and significant reduction of Side-Lobe and back-Lobe radiations in the operating frequency band.
H S Wu - One of the best experts on this subject based on the ideXlab platform.
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a new low Side Lobe pattern synthesis technique for conformal arrays
IEEE Transactions on Antennas and Propagation, 1993Co-Authors: Yongchang Jiao, L W Huang, H S WuAbstract:The application of the new nonlinear optimization algorithms to array design is demonstrated by the low-Side-Lobe pattern synthesis of conformal arrays. By adopting the information of array element realized gain patterns the authors formulate synthesis problems as nonlinearly constrained optimization problems, and propose a direct method to solve them. The technique allows them to find a set of array coefficients that yield a pattern meeting a specified Side-Lobe level and achieving the maximum directivity, if such a set of array coefficients exists. If the Side-Lobe specifications cannot be met with the given array, the technique will result in a set of coefficients that yield a pattern meeting the best attainable Side-Lobe level and having directivity as high as possible. Simplified synthesis problems for an axial dipole array in an infinite, perfectly conducting cylinder are discussed, and numerical results are given. The synthesis technique works for general array patterns. >
A Abusiada - One of the best experts on this subject based on the ideXlab platform.
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a minimum Side Lobe optimization window function and its application in harmonic detection of an electricity gird
Energies, 2019Co-Authors: Zhenhua Li, Tinghe Hu, A AbusiadaAbstract:Several window functions are currently applied to improve the performance of the discrete Fourier transform (DFT) harmonic detection method. These window functions exhibit poor accuracy in measuring the harmonic contents of a signal with high-order and weak-amplitude components when the power frequency fluctuates within a small range. In this paper, a minimum Side-Lobe optimization window function that is aimed at overcoming the abovementioned issue is proposed. Moreover, an improved DFT harmonic detection algorithm based on the six-term minimum Side-Lobe optimization window and four-spectrum-line interpolation method is proposed. In this context, the minimum Side-Lobe optimization window is obtained by optimizing the conventional cosine window function according to the optimization rules, and the characteristics of the new proposed window are provided to analyze its performance. Then, the proposed optimization window function is employed to improve the DFT harmonic detection algorithm based on the six-term minimum Side-Lobe optimization window and four-spectrum-line interpolation method. The proposed technique is used to detect harmonics of an electricity gird in which the six-term minimum Side-Lobe optimization window is utilized to eliminate the influence of spectrum leakage caused by nonsynchronous sampling of signal processing. The four-spectrum-line interpolation method is employed to eliminate or mitigate the fence effect caused by the inherent measurement error of the DFT method. Simulation experiments in two complex conditions and an experiment test are carried out to validate the improved performance of the proposed window. Results reveal that the six-term minimum Side-lode optimization window has the smallest peak Side Lobe when compared with existing windows, which can effectively reduce the interaction influence of spectrum leakage, improve the measurement accuracy of the DFT harmonic detection method, and meet the standard requirement of harmonic measurement in complex situations.
Sung Jae Kwon - One of the best experts on this subject based on the ideXlab platform.
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Assessment of Side Lobe Estimation Accuracy Using Side Lobe Free Image
2019 IEEE International Ultrasonics Symposium (IUS), 2019Co-Authors: Mok Kun Jeong, Sung Jae Kwon, Min Joo ChoiAbstract:In order to effectively suppress Side Lobes in ultrasound imaging, it is necessary to quantify the signal amplitude due to Side Lobes at imaging points. The received channel data before receive beamforming are modeled as a sum of sinusoids having different spatial frequencies depending on the angle incident on a receiving array. In the signal constituting the channel data, the signal due to the main Lobe has a DC frequency, whereas the signal due to the Side Lobe has a spatial frequency that is approximately proportional to the incident angle. Taking the Fourier transform of the received channel data after zero padding, we can accurately estimate Side Lobes. In computer simulation of ultrasound images, we generate ultrasonic echoes returned from random scatterers. Because we already know the position of all reflectors, we can separate the signals reflected due to the main and Side Lobes so that the true Side Lobe level at each imaging point can be computed accurately. The main Lobe image can be used as a gold standard for assessing a Side Lobe suppression filter. The true and estimated Side Lobes can be used in Side Lobe suppression filtering of ultrasound images. We obtained the conventional, true Side Lobe, and estimated Side Lobe images for an object containing a wire and a cyst using computer simulation in a 64 channel focusing system with a 5 MHz linear array transducer. In the hypoechoic cyst, the estimated Side Lobe is almost the same as the true Side Lobe. We confirmed that the estimated Side Lobe can effectively be used in Side Lobe suppression filtering. Therefore, it is feasible to quantitatively estimate Side Lobes from the channel data, and improve the performance of the Side Lobe suppression filter in ultrasound imaging.
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Side Lobe free medical ultrasonic imaging with application to assessing Side Lobe suppression filter.
Biomedical Engineering Letters, 2018Co-Authors: Mok Kun Jeong, Sung Jae KwonAbstract:When focusing using an ultrasonic transducer array, a main Lobe is formed in the focal region of an ultrasound field, but Side Lobes also arise around the focal region due to the leakage. Since the Side Lobes cannot be completely eliminated in the focusing process, they are responsible for subsequent ultrasound image quality degradation. To improve ultrasound image quality, a signal processing strategy to reduce Side Lobes is definitely in demand. To this end, quantitative determination of main and Side Lobes is necessary. We propose a theoretically and actually error-free method of exactly discriminating and separately computing the main Lobe and Side Lobe parts in ultrasound image by computer simulation. We refer to images constructed using the main and Side Lobe signals as the main and Side Lobe images, respectively. Since the main and Side Lobe images exactly represent their main and Side Lobe components, respectively, they can be used to evaluate ultrasound image quality. Defining the average brightness of the main and Side Lobe images, the conventional to Side Lobe image ratio, and the main to Side Lobe image ratio as image quality metrics, we can evaluate image characteristics in speckle images. The proposed method is also applied in assessing the performance of Side Lobe suppression filtering. We show that the proposed method may greatly aid in the evaluation of medical ultrasonic images using computer simulations, albeit lacking the use of actual experimental data.
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A novel Side Lobe estimation method in medical ultrasound imaging systems
2015 IEEE International Ultrasonics Symposium (IUS), 2015Co-Authors: Mok Kun Jeong, Sung Jae KwonAbstract:We propose a new method of estimating Side Lobes from received ultrasound channel data. Ultrasound signals impinging on an array transducer manifest themselves as sinusoids whose spatial frequency varies as a function of the incident angle. The channel data received from the main Lobe direction have a spatial frequency of zero because the individual channel data have the same phase, while those from the Side Lobe directions have a spatial frequency that is not zero and varies with the incident direction of an ultrasound beam. The Side Lobe waveforms in the received channel data are modeled as a sum of sinusoids having a spatial frequency of an integer plus a half. The window length is adaptively varied in the estimation of those Side Lobe waveforms. The effect of Side Lobes on ultrasound image can be reduced in receive focusing by subtracting the estimated Side Lobe waveforms. To confirm the efficacy of the proposed method, ultrasound field simulations were carried out. By estimating and subtracting the waveforms of the 1st to 20th spatial frequency Side Lobes, we were able to reduce the Side Lobe levels by up to 14 dB when imaging point targets.
