A TM31 Mode Circular Microstrip Patch Antenna with a Reduced Eigenvalue

A miniaturized TM31-mode circular microstrip patch antenna is presented. The patch is loaded with six symmetrically-placed radial slits, inspired by the surface current distribution of the mode. This will in turn facilitate elongating the current path and accordingly reduce the eigenvalue of the TM
31
mode. In particular, the realized eigenvalue is comparable to that of a conventional dominant TM11 mode antenna, resulting in about 72% reduction in the patch area.