Measuring reactive near-field interference using the quartz oscillators intermodulation

A quartz oscillator is susceptible to electromagnetic interference (EMI). To evaluate the effect of EMI, this research used the same quartz oscillator circuit for transmitter(s) and receiver(s), but with distinct quartz crystal (QC) frequencies. An equivalent impedance change occurred because of the reactive near-field feedback on the quartz oscillator. The strength was roughly proportional to the inverse transmitter-to-receiver distance. The unhoused QC, which functioned as a parallel and perpendicular receiver to the transmitter, displayed nondirectional and unidirectional radiation patterns, respectively. The intermodulation of the EMI transmitted from the QC oscillator was recognizable in the superposition feature.