A Passive Harmonic Tag for Humidity Sensing

Figure 14

Simulated signal-to-noise ratio by a harmonic tag and convention tag by backscattering at 𝑓₀ using a free-space model (a) and using a two-slope model with 𝑛₁=𝑛₂=2.5, and ℎ_reader=ℎ_tag=1.5 m. The required SNR limit of 11.6 dB for a 0.001% of BER is also shown.

(a)

(b)