I built coils for wireless power transfer. Found inductance with a LRC meter. Put capacitors, hoping for a resonant frequency at 300kHz. Student assisted me with a NVA machine where a resonant frequency 800kHz was found. It plots power transfer over frequency. My capacitor values were pretty off. Needed a .9micro farad and used a 1micro farad. Still a large shift from 300 to 800kHz. It had like 80% transfer over 2cm distance. The yellow line is S21 at 800kHz.
I also purchased wurht coils https://www.we-online.de/katalog/datasheet/760308111.pdf. Saw a high Q factor around 200-300kHz. Placed capacitors for 270kHz resonance. And they worked best at 303kHz. It lit an led from centimeters away!.
When I place a led on my coil design it doesn't light at all. My coils show power transfer on the NVA machine yet can't light up a led. Wurth coils work great wirelessly lighting up a led.
Could it be the Q facotr? Never payed attention to Q until I bought the wurth coils which inside their data sheet show high Q as a function of frequency.
Looked up the equitation for Q and got Q series = 2 pi f L / R. This graph should look liner with frequency. The Q data graph looks more complicated(maybe R changes with f). I'm lost. Why don't my coils light up a led, even with them almost touching(NVA says 95 power transfer). Also how would I calculate Q and better understand Q for my coils. I believe either the NVA machine was wrong or my S21 has a power sent so week, that my coils could not light a led. Maybe if I run my design at resonance and high Q value. Any tips or resources would help.