Coherent CPFSK Demodulation on ARM Cortex M Microcontrollers

In a new article on Habr, the author discusses methods for optimizing coherent CPFSK signal demodulation for ARM Cortex-M microcontrollers, including the STM32F103 and STM32H750. The focus is on efficiently calculating trigonometric functions using fixed-point Fourier series expansion, which achieves high precision with minimal CPU cycles. The author describes shifting from symbol-by-symbol processing to block-based correlation using a sliding window, significantly increasing computational speed and enabling real-time quadrature demodulation even on low-cost controllers. This approach provides a dynamic range sufficient for processing signals with bandwidths up to 125 kHz, offering new possibilities for implementing complex digital signal processing algorithms on resource-constrained embedded systems.