A Novel Digital Lock-In Amplifier With Extended Lyapunov Demodulation for Wide Dynamic Range Applications

Wide dynamic range is a critical requirement for precision instruments, demanding the ability to detect both weak and strong signals with high accuracy. This paper integrates dynamic range adjustment techniques into digital lock-in amplifier, enabling the adjustment of excitation signal amplitude to alter sensitivity without additional components. In this context, an extended Lyapunov demodulation algorithm is proposed, capable of simultaneously performing digital demodulation and sensitivity compensation, ensuring smooth signal extraction during dynamic range switching. Theoretical analysis and numerical simulations validate the algorithm’s effectiveness and performance. Finally, the proposed solution of digital lock-in amplifier is implemented on FPGA platforms, achieving dynamic range extension of 54.2 dB benefited from dynamic range adjustment, resulting in a total detectable voltage amplitude dynamic range of 226.2 dB. Applied to capacitive sensing, the system achieves detected capacitance dynamic range of 194.3 dB, demonstrating its capability for high-accuracy and wide dynamic range measurement applications.