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

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