A Rigorous 3D Near to Far Field Transformation when Only an Electric or Magnetic Field is Available

Due to a limited size anechoic chamber, it is sometimes not possible to directly measure far electromagnetic fields. Therefore, it is necessary to get these far fields from near field measurements in a surface surrounding our object or antenna. Furthermore, depending on the measurement technique, either the electric or the magnetic field is obtained but not both. For electrically small objects, such as a PCB, one could also use a quasistatic [1] simulation software. Depending on the technique we encounter a very similar situation, either electric or magnetic field on a surface surrounding the object is available. In this article, we present an approach to get equivalent electric and magnetic currents radiating the same fields as the original problem but into free space, making use of commonly existing integrals. This is simple when both fields are available but somewhat cumbersome when there is only one of them.