Loading effects of self-biased magnetic films on patch antennas with substrate/superstrate sandwich structure

From materials perspective, it has been challenging to achieve relative permeability μ _r>1 in self-biased antenna substrates at gigahertz frequencies. In this study, self-biased microwave NiCo ferrite films were deposited with a low-temperature spin spray deposition process. Novel antenna designs with self-biased NiCo-ferrite films were investigated at 2.1 GHz. These magnetic antennas with several micrometers thick ferrite films show an enhanced antenna performance over the unloaded patch antenna. With ferrite loading of the alumina substrate, the resonant frequency shows a down shift of 30-50 MHz. The radiation efficiency is increased from 41% for the non-magnetic antenna to 76% for the ferrite films loaded antenna, together with an antenna gain enhancement greater than 1 dB over the non-magnetic antenna. The combination of these self-biased ferrite films and alumina substrates can lead to miniature antennas with enhanced performance at gigahertz frequencies.