Automatic Directivity Index Calculation Program
Abstract
A computer program was written for the HP 9845 and the HP 9816 to calculate the directivity index directly from the beam pattern. A graphics tablet and stylus is used to digitize data points used to compute the directivity index. Graphical output is produced on a printer and plotter. This program was developed to enable the user to digitally input beam pattern data points into a computer and calculate the directivity index from this data. It eliminates the slow and monotonous task of visually determining the polar coordinates of the data points and manually keying them into the computer for processing. Prior to the creation of this program two methods were used to find the directivity index of a beam pattern. The first method involved extracting data from the beam pattern by reading a data point at specific, regular intervals. This method was slow and less accurate due to the fact that the operator introduced error when approximating the position of the data points. The second method required the beam pattern, which was plotted in a polar coordinate system, to be re-plotted in a rectangular coordinate system. This operation was performed by the user. Once this conversion had been completed, a mechanical device called a planimeter was used to calculate the directivity index. Obviously, this method was extremely slow. Therefore, this program greatly reduces the time and effort required to calculate the directivity index of a beam pattern. It also produces a more accurate result. The program requires an HP 9845 computer, an HP 9111A graphics tablet and an HP 9872A plotter. In addition, it requires that the Structured Programming ROM be resident in the HP 9845 computer. Without it, certain BASIC statements cannot be executed. A slightly modified version of this program is available for the HP 9816 computer. It provides the same capabilities as the HP 9845 version but utilizes an HP 7470 plotter instead of an HP 9872A plotter.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 23, 1984
- Accession Number
- ADA628379
Entities
People
- Jehu D. Rookard
Organizations
- Naval Underwater Systems Center