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.