kthackst
Member level 5
I'm working on an idea for a wireless sensor. My idea is to have a smartphone and a passive NFC tag. The tag operates as a sensor and is slightly detuned from the 13.56MHz resonance when it measures a large signal. I would like to be able to quantitatively measure this frequency shift on the transponder (smartphone) side.
From my knowledge of coupled inductive systems, I know it should be a simple manner to detect this frequency shift using just one port in a network analyzer plugged into the transponder resonator. S11 would be a function of the L, C, and Q on both antennas, in addition to the mutual inductance between them, so if the L on the sensor side is the only variable changing, I can measure it. But lots of things are easy on network analyzers.
Perhaps this is a problem better suited for the Digital Communication Forum, but how could I use NFC to detect this frequency shift? Can a smartphone using NFC measure anything close to Insertion Loss?
From my knowledge of coupled inductive systems, I know it should be a simple manner to detect this frequency shift using just one port in a network analyzer plugged into the transponder resonator. S11 would be a function of the L, C, and Q on both antennas, in addition to the mutual inductance between them, so if the L on the sensor side is the only variable changing, I can measure it. But lots of things are easy on network analyzers.
Perhaps this is a problem better suited for the Digital Communication Forum, but how could I use NFC to detect this frequency shift? Can a smartphone using NFC measure anything close to Insertion Loss?