These patch antennas leverage a multilayered copper/cobalt design to improve received signal power by reducing loss associated with alternating current oscillating at radiofrequency (RF). 5G cellular networks offer faster data rates and higher capacities than previous networks, enticing 1.6 billion consumers onto 5G networks as of 2023. However, their operation in the 24-36 GHz band of RF frequencies suffers from antenna power losses, which increase as more antenna array elements are added. These RF losses stem from the confinement of RF current to the surface of traditional nonmagnetic conductors such as copper. One mechanism to counteract this surface confinement is to set the magnetic permeability of the material as close to zero as possible. This is achievable by layering the copper conductor with a material possessing a very different magnetic permeability, forming a metaconductor with unusual properties attributed to the misalignment of the magnetic permeabilities of the layers. This breakthrough was successfully applied to reduce RF losses antenna transmission lines, but it remains important to reduce RF losses in other antenna components as well, especially in the patch antennas found in mobile phones.
Researchers at the University of Florida have developed a metaconductor patch antenna design constructed of stacked layers of nanometer-thin copper and ferromagnetic cobalt. The competition between the positive magnetic permeability of the copper and the negative magnetic permeability of cobalt results in a small effective magnetic permeability, reducing RF losses by destroying the surface confinement effect.
Suppresses power loss in patch antennas operating at 5G compatible radiofrequencies
Patch antenna arrays consist of many planar array elements connected to a receiver/transmitter by feedlines. Each of these carries alternating current at frequencies on the GHz scale, seven orders of magnitude greater than the alternating current supplied by wall outlets. Unsurprisingly, these high frequencies cause power loss for each array component. This power loss can be quantified via the skin depth of the component, which measures how deep into the surface the alternating current can manifest.
The skin depth is inversely proportional to the frequency of the current, resulting in the surface confinement effect at RF frequencies. This means only a tiny fraction of the conductor’s cross-sectional area very near the surface can transmit current, corresponding to significant power loss. Increasing the skin depth counteracts this power thanks to the inverse dependence of the skin depth on the effective magnetic permeability of the material. This quantity can be customized in multilayered structures by including materials with magnetic permeabilities of opposite sign. The metaconductor patch antenna design layers a few nanometers of nonmagnetic, conducting copper with ferromagnetic cobalt to achieve low effective magnetic permeability and boosted skin depth. As a result, it delivers signal power 6 decibels higher than a copper-only design for a typical 5G operating frequency.
