Evaluation of far-field pattern from near-field measurement using a near-field imaging technique

The authors propose a method to evaluate the far-field scattering pattern from measured near-field data. The basic concept of this method is that the far-field data (or the Fourier space data) and the complex far-field image have an FT (Fourier transform) relationship, and that the complex far-field image and the near-field image reconstructed by the spherical back-projection method have a similar appearance. In other words the far-field age can be approximated by the near-field image and the far-field scattering pattern can then be evaluated by inversely Fourier transforming the complex near-field image. The primary advantage of this method is that the far-field scattering patterns for different frequencies can be achieved simultaneously. However, this method is an approximate method. The far-field data so derived are valid only for those points contained in the original frequency and angular windows, and the scattering mechanisms of the object and the interpolation procedure can affect the accuracy of the derived results. An example of the application of this method is presented.<>