Relation between phase center and amplitude center of antenna by Kern transmission formula

The Friis transmission formula between two antennas is used to measure the gains of these antennas. Generally the gains obtained by the Friis formula at a finite distance are not the far-field gains because the far-field gain is defined to be a value at infinite distance. The gain at the finite distance is called as the near-field gain. To obtain the far-field gain from the near-field gain in measurement is an important topic [1].