Hi imobscure, thanks for the info, this makes sense now. I will obtain the sin/cos signals from the crossed polarisers, then use the analog multipliers.
Hi mixedgas, thanks for your kind offer. I am planning to use the analog calculation, because i think even 100us ADC-LUT-DAC delay would cause 3.6 degrees error at my target 6000 rpm, which is not acceptable.
I will let you know if it works!
weartronics