List of Articles Fast Fourier Transform (FFT)

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  1 - A Fast Method to Compute Radiation Fields of Shaped Reflector Antennas by FFT
  zaker hosseinfirooze abolghasem zeidabadinezhad hamid mirmohammadsadeghi
  A rapid calculation method of the far-field radiation patterns of a shaped reflector antenna illuminated by a feed in an arbitrary location is reported. In this method, the equations of geometrical optics (GO) are used to calculate the reflected electric field using the More

  A rapid calculation method of the far-field radiation patterns of a shaped reflector antenna illuminated by a feed in an arbitrary location is reported. In this method, the equations of geometrical optics (GO) are used to calculate the reflected electric field using the radiation patterns of the feed and the parameters defining the reflector surface. These fields comprise the aperture field distribution which is integrated over the aperture plane by Fast Fourier Transform (FFT) algorithm based on low-size meshing of the aperture to yield the far-field radiation patterns and to calculate other antenna parameters. Shaped Reflector Antenna Design and Analysis Software (SRADAS) based on this numerical method can analyze and simulate all shaped reflector antennas with large dimensions in regard to the wavelength. SRADAS has been implemented and used in Information and Communication Technology Institute (ICTI) to analyze and simulate different practical parabolic and shaped reflector antennas. In order to confirm the integrity of the proposed calculation method, two practical antennas are analyzed using this software. The results are in good agreement with the results obtained by commercial software (Method of Moment) and measurement. Large shaped reflector antennas can be simulated by SRADAS fast and accurately. Manuscript profile
• Open Access Article
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  2 - Defect Detection using Depth Resolvable Statistical Post Processing in Non-Stationary Thermal Wave Imaging
  G.V.P. Chandra  Sekhar Yadav V. S.  Ghali Naik R.  Baloji
  10.52547/jist.15690.10.38.132
  Defects that are generated during various phases of manufacturing or transporting limit the future applicability and serviceability of materials. In order to detect these defects a non-destructive testing modality is required. Depth resolvable subsurface anomaly detecti More

  Defects that are generated during various phases of manufacturing or transporting limit the future applicability and serviceability of materials. In order to detect these defects a non-destructive testing modality is required. Depth resolvable subsurface anomaly detection in non-stationary thermal wave imaging is a vital outcome for a reliable prominent investigation of materials due to its fast, remote and non-destructive features. The present work solves the 3-Dimensional heat diffusion equation under the stipulated boundary conditions using green’s function based analytical approach for recently introduced quadratic frequency modulated thermal wave imaging (with FLIR SC 655A as infrared sensor with spectral range of 7.5-14µm and 25 fps) to explore the subsurface details with improved sensitivity and resolution. The temperature response obtained by solving the 3-Dimensional heat diffusion equation is used along with random projection-based statistical post-processing approach to resolve the subsurface details by imposing a band of low frequencies (0.01-0.1 Hz) over a carbon fiber reinforced polymer for experimentation and extracting orthonormal projection coefficients to improve the defect detection with enhanced depth resolution. Orthonormal projection coefficients are obtained by projecting the orthonormal features of the random vectors that are extracted by using Gram-Schmidt algorithm, on the mean removed dynamic thermal data. Further, defect detectability of random projection-based post-processing approach is validated by comparing the full width at half maxima (FWHM) and signal to noise ratio (SNR) of the processed results of the conventional approaches. Random projection provides detailed visualization of defects with 31% detectability even for deeper and small defects in contrast to conventional post processing modalities. Additionally, the subsurface anomalies are compared with their sizes based on full width at half maxima (FWHM) with a maximum error of 0.99% for random projection approach. Manuscript profile