The impedance of a monopole antenna with a circular conducting-disk ground system on the surface of a lossy half space

Abstract

T he b ase imp edance of a A/ 4 mo nopole antenna w it h a circular condu cting di s k grou nd ~ystem o n t he surface of a l ossy ha lf-space is calculated as a fu nction of di s k diamete r using t h ree d iffe r ent app roximate met hods. Ve rify ing m easu rements were ma d e on a mod el at X-band fr equ encies by simulat ing the lossy ha lf-space wi t h a wate r fill ed tank sufficiently large to approxi mate t he res ul ts expected fro m a n infini te lossy g ro u nd. Th e meas ured impeda nce values, Z, we r e br oken up i nto t he sum of two te rms t:.Z and Zoo w he re Z oo i t h e i mpedance of t he a ntenna with a pe rfectly condu cting g rou nd a nd t:.Z is a te rm wh ich accounts for t he fi nit e size of t he di s k. T he expe ri mental rneas urements 0 11 a number of GLn tcllnas indi cate t hat t he ratio t:.Z /Z oo as a fu nction of di s k di amete r is nead y t he sarn(' fo r ",11 ",ntennas m eas u red. Co mparison of t he m.eas ured "",Ill es of t hi s nLt io " Ild t he values ca lcul ",tcd by t he th r ee d ifl"e rent app rox imate m. et hods indi cate q ua li tative agree m.en l.

On the Near-field of an Antenna and the Development of New Devices

“…The above information may be used for dimensioning the ground of a monopole antenna (for an overview the reader is addressed for instance to [15]). Early experimental results, for many choices of the disk diameter, were conducted in [13]. From the theoretical viewpoint, the monopole is usually regarded as a half-space dipole.…”