Open hardware near-field probes

[loxodes]

I've been lurking around these forums for a few weeks without posting, so I thought I'd share the first-order approximation of near field probes that I built recently: https://github.com/loxodes/em_probes/

https://github.com/loxodes/em_probes/tree/master/doc has coupling measurements of the probes above microstrip, They aren't perfect, but seem to work up to about 6 GHz. So far they've been helpful at probing a board that I didn't put enough test points on.. I've never used or seen proper near-field probes before, I welcome any feedback on how to improve the design.

If anyone wants to try replicating or modifying these, the layout assumes the OSH Park 4 layer stackup (http://docs.oshpark.com/services/four-layer/); y'all would need to modify the offset stripline for other stackups. The stripline was simulated with the MMTL open source 2.5D EM simulation software (https://sourceforge.net/projects/mmtl/files/tnt/1.2.2/), it could be helpful for tuning this to other board houses.

The h-field probe design was almost copied frominspired by "Study of Magnetic Probes Used in EMI Measurements" (http://www.apemc2015.org/Proceeding/papers/1570059913.pdf)

[daqq]

Nice work!