NEAR-FIELD SCATTERING OF WAVES FROM A STATISTICALLY ROUGH SURFACE: IV. FREQUENCY SPECTRUM IN THE CASE OF OBLIQUE MONOSTATIC RADAR SOUNDING

2011 ◽  
Vol 2 (2) ◽  
pp. 133-137
Author(s):  
A. S. Bryukhovetsky
Keyword(s):  
Rough Surface ◽  
Frequency Spectrum ◽  
Near Field

scholarly journals Observation of photoacoustic Smith-Purcell radiation

2021 ◽  
Author(s):  
Dongyi Shen ◽  
Zhihao Zhou ◽  
Guolin Zhao ◽  
Xianfeng Chen ◽  
Wenjie Wan
Keyword(s):  
Shock Waves ◽  
Frequency Spectrum ◽  
Acoustic Radiation ◽  
Near Field ◽  
Critical Role ◽  
Universal Theory ◽  
Relativistic Electrons ◽  
Radiation Process ◽  
Constant Frequency ◽  
Acoustic Wave Generation

Abstract Relativistic electrons moving over a periodic metal grating can lead to an intriguing emission of light, known as Smith-Purcell radiation (SPR), the precursor of the free-electron laser. During the radiation process, the speed of light plays a critical role in determining the emitted angle and frequency spectrum. Inspired by the photonic SPR, here we experimentally demonstrate a photoacoustic version of the Smith-Purcell effect using laser-induced surface shock waves generation. We observe similar acoustic radiation pattern and their associated frequency spectrum in the far-field, perfectly predicted by a universal theory working for both the photonic and acoustic SPR. Moreover, our numerical studies reveal non-constant frequency components due to the supersonic traveling of the shock waves in the near field, greatly contrasting its photonic counterpart. This scheme extends the SPR into the acoustic domain by levitating the wave’s speed limit, paves the way towards coherent acoustic wave generation and microstructure metrology.

Measuring the characteristics of backscattering of sound on a rough surface in the near-field zone of a phased array

2016 ◽  
Vol 62 (1) ◽  
pp. 74-88 ◽  
Author(s):  
M. B. Salin ◽  
O. A. Potapov ◽  
B. M. Salin ◽  
A. S. Chashchin
Keyword(s):  
Rough Surface ◽  
Phased Array ◽  
Near Field ◽  
Field Zone

scholarly journals A Novel Hybrid Algorithm for Transient Near-Field Scattering from Rough Surface in 2-D Case

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Wei Tian ◽  
Bing Wei ◽  
Qian Yang
Keyword(s):  
Rough Surface ◽  
Time Domain ◽  
Hybrid Algorithm ◽  
Near Field ◽  
Scattering Problem ◽  
Fdtd Method ◽  
Observation Point ◽  
Surface Integral ◽  
Field Radiation ◽  
Direct Numerical Integration

A novel hybrid algorithm is proposed to reduce the computation cost of the finite-difference time-domain (FDTD) method in calculating the transient near-field scattering from rough surface. The scattering problem is split into the FDTD calculation of equivalent sources on the contour enclosing rough surface and the calculation of the near-field radiation with the two-dimensional (2-D) time-domain Huygens’ principle. The radiation fields are found from a surface integral of the temporal convolution for which the direct numerical integration of the convolution is computationally expensive. In this paper, the 2-D time-domain Green’s function as the convolution kernel is approximated with a sum of exponential terms by using the Prony’s method. Then, the semianalytical recursive convolution (SARC) approach is applied to complete the update of the near-field radiation. Compared with the traditional FDTD, this hybrid algorithm can significantly reduce the memory usage and run time, especially for the large distance between the rough surface and observation point.

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