Next generation communications

For complex radio frequency and power electronic devices – like phased array radar systems, electronic warfare equipment, and base stations, which can extend a cellular provider’s network by blocks or by miles – high performance monolithic microwave integrated circuits (MMICs) with integrated passive ferrite devices are crucial components. Ferrite devices provide self-biasing, low insertion loss, and high power handling capability, while also improving circulation and isolation in RF/Microwave devices.

With the advent of low-cost, easy-access modern communications, lower frequency spectra are becoming increasingly congested. The millimeter wave spectra presents a promising alternative, and with that comes a need for high-power and low-cost devices able to operate in that frequency band.

At those frequencies, the materials currently in use are barium and strontium hexagonal ferrites. A communication system for the millimeter wave spectra would require a low noise amplifier, a highly efficient power amplifier, and a nano-ferrite circulator. As part of developing those components, manufacturers or researchers need to apply a very thin film of material, the thickness of only a few atoms, onto a substrate surface.

A significant challenge arises when attempting to deposit a self-biased hexagonal ferrite thin film that is both high quality and can be manufactured at low cost. That’s where Associate Professor Valencia Koomson and Professor Mohammed Nurul Afsar’s work comes in.

In a three-year research proposal funded by the National Science Foundation, Afsar and Koomson seek to develop a hexagonal ferrite thin film preparation system that will be applicable to wide-bandgap semiconductors, which allow devices to operate at higher temperatures, frequencies, and voltages than conventional semiconductor materials. That system would be applicable to silicon substrates for the next generation of ferrite devices operating in the millimeter wave frequency range.

In addition to the development and implementation of that thin film deposition system, Afsar and Koomson are working on the first in-depth study of self-biased hexagonal ferrite on GaN-on-SiC substrates, and fabricating a demonstration passive millimeter wave device.

The final aspect of their project will help develop the next generation of engineers and scientists studying the emerging area of miniaturized ferrite devices and related materials science and engineering. In collaboration with the Tufts Center for Engineering Education and Outreach, they will develop learning modules for public high school teachers, in addition to providing undergraduate and graduate learning opportunities in device design and nanofabrication, electromagnetic modeling and simulation, and materials science.

In the process of designing an efficient circulator nonconductive, bonding material plays a major role because the material fills the gaps between the base material (GaN) and the thin layer of nano-ferrite powder of Barium/Strontium sprayed using spray pyrolysis method. The thin film layer deposited on the base material should be uniform to achieve the desired electrical performance.  

This work was supported by the National Science Foundation (#1808147).