We have an size critical application in which we intend to use passive NFC (there is no room for battery). In the application we have a one variable resistor which value we would need to transmit using NFC. Considering that our signal is analog we are now asking if there is any smart way to feed the signal to NFC IC which could subsequently transmit it? We started thinking about oscillators where the varistor would change the frequency.
We haven't yet selected the NFC IC and if there is some certain NXP product that would fit here, we would love to hear about it.