Complex Impedance Plane Drift Compensation in Resonant Inductive Front Ends
Orthogonal vector decomposition of complex impedance separates resistive copper thermal drift from reactive target motion in high-Q resonant inductive sensors.
Dual Frequency Excitation
Signal Drive
MEMS sensor interrogation systems apply two distinct sinusoidal signals to separate carrier modulation from structural dynamics. Dual frequency excitation drives a resonant structure at its primary mechanical frequency while simultaneously applying a secondary high frequency carrier to detect displacement. The primary frequency excites structural motion while the secondary carrier reads capacitive changes without altering mechanical dynamics.
Capacitive interface circuits isolate structural motion signals from parasitic coupling.
Bandwidth Modulation
Separating drive and sensing channels across two frequencies prevents electrical feedthrough from distorting displacement readings. High frequency carrier signals shift capacitive variation data far above the mechanical resonance band. Demodulation circuits extract physical position measurements without phase delay or amplitude distortion from drive signals.
Sensing resolution improves because carrier frequencies avoid low frequency flicker noise bands.
Spurious Coupling
Nonlinear capacitive responses produce intermodulation products when primary and secondary frequencies interact within sensor electrodes. Unwanted mixing terms create spurious spectral tones near the detection passband. Filtering networks attenuate intermodulation signals to preserve sensor output linearity.
Spurious tone control requires precise frequency spacing between drive and carrier sources.
Test Protocol
Bench verification measures harmonic distortion across specified carrier drive voltage ranges. Spectral analysis confirms intermodulation products remain below target decibel levels relative to the carrier signal. Automated calibration sequences set drive and carrier amplitudes to maximize signal to noise ratios.
Target Material Impact on Inductive Sensing Distance Reduction Factors
Target material conductivity and permeability set inductive sensing distance reduction factors, reducing nominal operating range by up to seventy percent.