Introducing Quanta Control: FPGA Feedback at 125 MHz
Why FPGA-Based Feedback Control?
In precision measurement and quantum technology, the feedback controller is often the critical bottleneck. Whether you're locking a laser to a cavity, stabilizing a piezo actuator, or reading out a precision sensor, the loop bandwidth and latency of your controller determine how well you can suppress noise.
Traditional solutions fall into two categories:
- Analog controllers — fast but inflexible, difficult to reconfigure
- Digital controllers on CPUs/DSPs — flexible but limited by OS jitter and bus latency
- •A Xilinx Zynq-7010/7020 SoC (FPGA + dual-core ARM Cortex-A9)
- •Two 14-bit ADC channels at 125 MSPS
- •Two 14-bit DAC channels at 125 MSPS
- •Ethernet connectivity for remote control
- •Multi-tone DDS signal generation — three independently configurable sine waves for system identification and disturbance simulation
- •6-stage CIC decimation filter — reduces the 125 MSPS sample rate to 1 MSPS with excellent stopband rejection
- •Fixed-point PI controller — Q16.16 arithmetic with anti-windup clamping
- •Configurable output MUX — route any internal signal to the scope for monitoring
- •Additional filter topologies (IIR, FIR)
- •Multi-loop control for complex systems
- •Automated system identification and loop tuning
- •Integration with popular lab software frameworks
FPGA-based controllers offer the best of both worlds: the speed of dedicated hardware with the flexibility of software-defined signal processing.
Our Architecture
Our system is built on the Red Pitaya platform, which provides:
On the FPGA fabric, we implement:
All parameters are accessible through an AXI4-Lite register interface, which the ARM CPU exposes via a REST API. A Vue.js web application provides real-time oscilloscope display, parameter tuning, and Allan deviation stability analysis.
What's Next
We're actively developing:
Stay tuned for technical deep-dives into each component of the system.