The spherical near-field far-field technique and its application to satellite antennas

The spherical near-field technique (SNFT) has recently been implemented and tested in the Radio Anechoic Chamber at the Technical University of Denmark. The technique was demonstrated for a cylindrical satellite model with and without solar panels. The near and far fields were measured, and the predicted and the measured far fields were compared. The main results presented are: it is possible by SNFT to predict far fields with an accuracy the same or even better than by direct far-field measurements; the highest degree, N, of the modes required in the expansions of the field is traditionally stated to be 2 pi r sub o / lambda where r sub o / lambda is the radius (in terms of wavelengths) of the smallest sphere surrounding the test antenna. It has been demonstrated that for certain applications a much smaller number of modes are sufficient; and it is possibile to truncate the measurement surface - not only to the region of high field intensity but, roughly, to the region of interest.