Multi Coil Quadrature Demodulation Signal Chains for Proximity Measurement
Multi coil quadrature demodulation isolates amplitude and phase in inductive proximity chains, resolving sub-micron targets while rejecting thermal noise.
Baseline Zero Crossing
Threshold Detection
Voltage comparator circuits locate the exact temporal instance where an AC waveform passes through zero electrical potential. A baseline zero crossing establishes the time reference for phase measurement and frequency counting systems. Offsets in amplifier bias alter this temporal reference, creating duty cycle asymmetry in the generated pulse train.
Differential comparator topologies minimize offset drift caused by temperature variation across the operating range.
Hysteresis Margin
Positive feedback loops prevent erratic output switching caused by low-amplitude input noise. Introducing hysteresis around a baseline zero crossing stabilizes edge generation but introduces a deterministic phase lag. Factory calibration establishes the exact switching thresholds to balance noise immunity against phase accuracy.
Phase Delay
Propagation delays through input filters shift the detected transition relative to the actual input zero crossing. High-frequency attenuation delays the baseline zero crossing, requiring phase compensation in downstream processing logic. Correcting this timing shift ensures accurate power factor calculation in grid monitoring equipment.
Noise Susceptibility
Broadband thermal noise creates false trigger pulses when signal slew rates drop near zero. Low signal-to-noise ratios degrade the precision of a baseline zero crossing by creating timing jitter. Preamplifier gain must remain sufficient to maintain steep edge transition rates through the zero region.