Fig. 5: In-lab characterization of HARVEST sensor sensitivity to soil VWC and EC.
a (i) Top view of prepared soil samples with varying VWC levels of 10%, 15%, 20%, and 25%; (ii) Placement of HARVEST sensor within the soil sample. b Wireless measurement setup using a Horn Reference Antenna (HRA) and c Portable Reader Antenna (PRA) as RF interrogator inside an anechoic chamber. Calibrated \({S}_{11}\) spectral responses of HARVEST with d varying VWCs (10%–25%) and e ECs (0.01-0.8 dS/m) using both HRA and PRA. f Calibration curve showing the differential resonant frequency shift of the VWC resonator (SRRVWC) relative to the reference resonator (SRRRef) as a function of VWC for different read distances. g Relative change in peak amplitude of the EC resonator (|SRREC||) normalized to the reference resonator (|SRRRef|) as a function of EC for different read distances. (Color-coded resonance peaks in spectra: Orange: EC resonator (SRREC), Blue: VWC resonator (SRRVWC), Green: Reference resonator (SRRRef)). f, g: Shaded region represents the 95% CI of the linear fit. Source data for Fig. 5 are provided as a Source data file.
