Abstract-A fast spherical near-field to far-field transformation using single cuts is introduced in this paper. It is based on calculating the Cylindrical Modal Coefficients of each individual near-field ring and processing them independently, considering them as cylinders of zero height and applying probe correction. The reconstruction of each far-field cut is obtained through an inverse Fast Fourier Transform. This procedure provides the opportunity to perform real time transformations due to its low acquisition and processing time. It is a useful tool for applications which do not require a full or accurate characterization, such as measuring the main patterns of an antenna or its most important parameters (peak gain, beam width, side lobe level, etc.).
A method to reduce the noise power in far-field pattern without modifying the desired signal is proposed. Therefore, an important signal-to-noise ratio improvement may be achieved. The method is used when the antenna measurement is performed in planar nearfield, where the recorded data are assumed to be corrupted with white Gaussian and space-stationary noise, because of the receiver additive noise. Back-propagating the measured field from the scan plane to the antenna under test (AUT) plane, the noise remains white Gaussian and space-stationary, whereas the desired field is theoretically concentrated in the aperture antenna. Thanks to this fact, a spatial filtering may be applied, cancelling the field which is located out of the AUT dimensions and which is only composed by noise. Next, a planar field to far-field transformation is carried out, achieving a great improvement compared to the pattern obtained directly from the measurement. To verify the effectiveness of the method, two examples will be presented using both simulated and measured near-field data.
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