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.
Active Shielding
Noise Suppression Strategy
Electromagnetic interference reduction relies on the generation of opposing fields to cancel out unwanted external signals. Active shielding utilizes electronic feedback loops to drive current through secondary coils or conductive structures. Sensors in high interference environments often deploy this method to protect low level signals from power line noise or stray magnetic fields.
Success depends on the phase accuracy of the cancelling signal relative to the noise source.
Compensating Coil
Compensation circuitry monitors the local field environment using a reference magnetometer or a dedicated sensing winding. Then active shielding applies a proportional counter current to maintain a zero field condition within the protected volume. This configuration creates a dynamic barrier that adapts to changing external conditions.
Passive materials like mu-metal saturate in strong fields, whereas active systems maintain performance until the driver reaches its current limit.
Suppression Ratio
Effectiveness is quantified by the ratio of the external field strength to the residual field inside the shielded zone. Because the feedback loop has a finite bandwidth, active shielding provides high attenuation at low frequencies but declines in performance as the noise frequency increases toward the loop crossover point. Phase shifts in the amplifier chain limit the maximum achievable rejection.
Power Consumption
Driving large currents through compensation coils generates heat and requires a stable power supply. Careful placement of the feedback sensor prevents the system from oscillating or cancelling the intended measurement signal. Proper calibration ensures the nulling field does not introduce additional drift into the primary sensor reading.