Corporate telecommunications labs testing 5G networks need analyzer equipment outfitted with these extreme isolators to make sure the new systems function properly. Because new high-speed cell phone bandwidths are in the millimeter range, it is important to test how these frequencies behave in several environments. Now Micro Harmonics is seeing interest from universities and laboratories around the world. They were able to get the low-loss isolators to work at 100 gigahertz, and subsequent developments achieved frequencies in excess of 330 gigahertz. The company also replaced the thermally insulating support washers used to suspend the ferrite in the waveguide with a diamond disc, which channels heat away from the resistive layer. Micro Harmonics shortened this core to its minimum possible length and tuned the magnetic field, significantly reducing the signal loss. Typical isolators use a long, magnetized ferrite core, which is responsible for most of the signal loss. They realized the solution was in the materials.
Under a Small Business Innovation Research (SBIR) contract with JPL, the team at Micro Harmonics in Fincastle, Virginia, developed a hand-built Faraday rotation isolator that could work at much higher frequencies and at higher power levels. However, existing isolators maxed out slightly above 100 gigahertz – about a three-millimeter wavelength – and caused a high level of signal loss. NASA’s Jet Propulsion Laboratory in Southern California needed isolators that worked with these wavelengths to conduct spectrometer experiments. Instruments aboard Earth-observation aircraft and satellites, such as spectrometers, take measurements in wavelengths of a few millimeters or smaller. Isolators use this principle to rotate reflected signals into a resistive layer that absorbs them. The Faraday effect, discovered in 1845 by Michael Faraday, states that magnets in a ferrite material can change the polarization of an electromagnetic signal.
Devices called Faraday rotation isolators are used in all kinds of equipment to suppress these standing waves. When a signal and its reflection intersect, they produce standing waves which can seriously degrade system performance. In sensing devices across the electromagnetic spectrum like radar systems, structural elements called waveguides are used to direct signals between components, but their design can cause reflections. It’s very important that the highly tuned components in sensitive instruments, whether on a spacecraft or used in a lab, don’t see their own reflection.
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