Characteristic Mode Analysis of H-shaped Slot Patch Antenna with Class-F Load Function

This paper proposes an H-shaped slot patch antenna with a class-F load function, which is useful for microwave power transfer. The class-F load function is realized by inserting two H-shaped slots into the patch element of an antenna and adjusting its microstrip line length. The reflection coefficient at the fundamental wave frequency is −32.1 dB, and the magnitude and phase of the reflection coefficient at the third harmonic frequency are −0.65 dB and 0.01°, respectively. We also elaborate on the proposed antenna principle through characteristic mode analyses. It is confirmed that only the TM01 mode current changes upon inserting slots into the patch antenna, which decreases the reflection coefficient at the fundamental frequency.