How to eliminate encoder feedback loop noise?

Noise in the encoder feedback loop can originate from power supply, ground, or spatial coupling, causing position feedback jumps. The Echotronics noise cancellation solution addresses this by:

First, isolating the noise source by placing the encoder feedback circuit (including the receiver chip, FPGA, etc.) in a separate PCB area and powering it with an isolated power supply module (such as a DC-DC converter). The isolation ground and power ground are connected at a single point via a ferrite bead (PBZ1608A-102Z0T).

Second, a hardware filter is used before the signal enters the processing chip: the differential signal passes through a common-mode choke (CML3225A-510T) and then through an RC low-pass filter (e.g., R=100Ω, C=47pF) with a cutoff frequency slightly higher than the signal frequency. Simultaneously, digital filtering algorithms such as median filtering or moving average are used in the software.

Finally, the PCB layout is optimized, maintaining a complete ground plane below the feedback loop.

Through this hardware and software combination, the counting error caused by feedback noise can be reduced by more than 95%, ensuring the positioning accuracy of the servo system during high-speed operation.