Radiation Pattern Stability and Miniaturization Improvements of Planar Antennas for Radar and Medical Imaging using the Theory of Characteristic Modes

This paper uses the Theory of Characteristic Modes (TCM) to study the radiation pattern stability and reduce the size of a circular planar antenna. A comparative study of different shapes is conducted to carry out high-resolution image performances of cancer tumors for better medical treatment and radar system detection applications. This study shows how each characteristic mode’s resonant frequency, half power bandwidth (HPBW), and modal pattern stability factor (MPSF) depend on the geometrical parameters. The use of a modal pattern stability factor demonstrates that the magnetic modes of the modified antenna have the best radiation pattern stability, with a high reduction in size compared to the conventional antenna by 46% in some cases. More reduction in size and radiation pattern stability can be obtained in periodical structures based on the technique used in this paper.