Does the NSI software integrate over the measured radiation patterns to obtain the directivity (ie the usual way of obtaining directivity)?
NSI2000 does calculate directivity in the “usual” surface integral way. Some extra detail re. polarization: The NSI 2000 program uses the output from the spherical wave expansion code after converting from theta phi components to the polarization components specified in the far-field menu. This data array always covers the complete sphere and so the integration of the pattern to obtain the radiated power is always over the full sphere regardless of the far-field spans in the far-field menu. As defined by international standards, both gain and directivity are total power quantities and are defined in terms of the total power per unit solid angle and therefore should be independent of the polarization components used to represent the field or the polarization of the antennas used to measure the field. In almost all uses of gain standards however, the quantity of most value is the partial gain for the main component of the antenna. Since in most cases the cross polarization of the antenna
