Size reduction of microstrip LPDA antenna with top loading

抄録

In this paper a reduced size microstrip log periodic dipole antenna with top loading of elements is presented. In many situations, the lateral size of the LPDA antenna has to be reduced to fit the antenna into the installation space. In this work, top loaded element structure is adopted to reduce the size of the dipole elements. Each straight dipole element of the LPDA antenna is turned into a T-shaped element whose total length is equal to that of the original straight dipole element length, resulting in a dipole length that is half that of the original dipole element, i.e. lateral size of the LPDA has been reduced by more than half. This procedure can be repeated to reduce the dipole element length even further, by placing a double T-shaped element on top of each other, resulting in an overall length that is almost 46% of the original dipole element length. Comparison of the reduced sized LPDA with that of the original LPDA shows that the VSWR (≤ 2.0) results of the reduced size LPDA are lower than those of the straight elements over the 2.3-8GHz frequency band. For the three LPDA structures results of peak gain shows that on average over the frequency band, 2-8GHz, gain varies between 5-6dBi. Simulation and measured results on VSWR, radiation pattern and gain at the various frequencies are provided.