ACCURATE MODELING OF STEPPED-RADII ANTENNAS

Abstract

The LP8, eight element, log periodic antenna made by M2 Enterprises has recently been modeled at Penn State University using both Version 2 and 4 of the Numerical Electromagnetics Code (NEC). The antenna has a steppedradii element construction and operates from 10 to 30 MHz. The stepped-radii element construction is difficult to model using NEC Version 2. To model a stepped-radii antenna with this version, equivalent lengths of constant radii are calculated using another method of moments program called ELNEC. These equivalent lengths replaced the original stepped radii elements of the log periodic antenna during the modeling. Fortunately, NEC Version 4 can simulate the stepped-radii elements directly, which makes the modeling procedure much easier and accurate. Both NEC models show good agreement with the measurements when compared to VSWR measurements. The authors hope that this paper will help others with similar modeling problems who cannot yet obtain NEC Version 4. [Vol. 10, No. 2 (1995), pp 86-95]