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.
Synchronous Detection
Coherent Signal Recovery
Periodic sampling or modulation techniques synchronized with a known reference frequency isolate specific information from a noisy background. Industrial sensors use synchronous detection to eliminate the effects of ambient light or stray electromagnetic fields. By pulsing a source and only measuring during those pulses, the system ignores any constant or unrelated signals.
This method provides a significant improvement in the signal to noise ratio.
Locking Process
The receiver must perfectly match the timing of the transmitter to function correctly. If the signals are out of phase, the recovered amplitude will be lower than the true value. Then synchronous detection employs a phase locked loop to maintain this alignment even if the source frequency shifts slightly.
This robustness makes it suitable for field applications where conditions are unstable.
Out Of Band Suppression
Any interference that does not share the exact frequency and phase of the reference is averaged to zero over time. Unlike a standard filter, synchronous detection can have an extremely narrow equivalent bandwidth. This allows for the detection of very weak signals without needing expensive high quality analog filters.
The integration time of the detector effectively sets the width of this filter window.
Switching Implementation
In simple systems, a set of switches reverses the gain of an amplifier in sync with the reference. This reversing action acts as a hardware multiplier. Precise timing is necessary to avoid switching transients that could add errors to the measurement.