A novel FPGA-Based Multi-Channel Signal Acquisition System Using Parallel Duty-Cycle Modulation and Application to Biologic Signals: Design and Simulation

Abstract

This paper presents the design and simulation of a new FPGA-based multichannel signal acquisition system, involving parallel DCM (duty-cycle modulation) of four biologic signals, i.e., respiratory, PPG (photoplethysmography), ECG (electrocardiography) II and V. Then, the resulting modulated inputs are simultaneously oversampled and converted into digital waves, by a low-pass decimation IIR (infinite impulse response) filter per channel. The relevant novelty brought by this new multichannel signal acquisition scheme, relies on a number of merits, e.g., 01 basic DCM circuit and 01input pin (or bit) of the FPGA per analog channel, IIR filter with 30 Hz cut-off frequency per channel (then no need of 50 or 60 Hz notch filters). As   relevant merits,  the proposed multichannel architecture offers minimum interfacing hardware while requiring minimum software resources. The virtual model of that acquisition system, is designed and implemented in Matlab/Simulink framework, using: a) modulating   biologic signals imported from Physionet bank; b) Simulink blocks for DCM interface; DSP Builder blocks (for parallel IIR filters); c) 50 MHz sampling frequency, with  60 bits precision coefficients; and d) virtual oscilloscopes. The predicted results presented for 04 biologic signals, are very satisfactory. In future research works, the VHDL code will be generated and compiled in Quartus II for uploading into DE10-NANO-SoCFPGA, in order to build our new FPGA-based multichannel biomedical instrument.