Dual-Unit ECG Acquisition System Without Shared Ground: Design and Implementation

This paper presents the design, simulation, and experimental validation of a distributed wireless electrocardiographic (ECG) acquisition architecture based on two electrically independent sensing units and a receiving unit. The two sensing units can be positioned at different locations on the body, where they independently acquire biopotential signals and transmit them wirelessly to a common receiver. The received signals are then differentially processed to reconstruct the ECG signal without requiring a shared ground reference between the acquisition units. The receiving unit could be implemented in future wearable realizations as a portable processing device, such as a smartphone, potentially enabling additional real-time ECG analysis. The aim is to enable signal acquisition and wireless communication without a shared ground reference between devices, thereby improving user mobility and supporting wearable biomedical applications. The MATLAB/Simulink R2024b model was employed to simulate the complete sensing and communication chain, including signal acquisition, transmission, reception, and differential reconstruction. The proposed acquisition architecture was subsequently implemented on a breadboard using discrete components, with isolation amplifiers used to emulate the electrical independence of wireless transmission. In addition, a separate preliminary experiment using independent ADALM2000 platforms was conducted to investigate the feasibility of signal transmission through a short-range wireless link. Simulation results showed that conventional amplitude modulation (AM) and double-sideband suppressed-carrier (DSB-SC) transmission achieved SNRs of 20.5 dB and 28.9 dB, and RMSEs of 2.12×10-4 and 8.01×10-5, respectively, with the DSB-SC performance obtained assuming perfectly synchronized carriers at the transmitter and receiver. Experimental validation of the proposed acquisition architecture using real ECG recordings demonstrated reliable ECG reconstruction, yielding SNR values of up to 19.7 dB together with accurate heart-rate (HR) estimation. A separate preliminary experiment using two independent ADALM2000 platforms further demonstrated the feasibility of ECG signal transmission and reconstruction through a short-range wireless link, achieving a reconstruction SNR of up to 13.5 dB.