Loop-Gap Resonators (LGRs) are a class of microwave resonators/cavities that are frequently used in Electron Paramagnetic Resonance (EPR) spectroscopy. LGRs were introduced in the 1980s by Hyde et al. as an alternative to the widely used rectangular TE102 or the cylindrical TE011 EPR cavity.
Here, we present a simple method to build an LGRs from printed circuit boards (PCBs). The resonator is easy to assemble and does not require any specialized machining techniques. The resonator is constructed from a set of PCBs, off-the-shelf hardware components, and 3D printed parts. The presented resonator is not a high-rend research tool but a teaching tool, to explore LGRs.
More information be found at: https://www.bridge12.com/learn/open-pcb-lgr/