PLI Cancellation from Biomedical Signals Using VDTA-Based Notch/Comb Filter

This research article presents a novel VDTA-based notch and comb filters and their application in suppressing power-line interference from low-frequency biomedical signals. They use a lesser number of active and passive components. First, it discusses the design of a single VDTA-based notch filter. Then by cascading four such notch filters, a comb filter is designed to eliminate one fundamental frequency and three consecutive odd harmonics. These filters' quality factor and pole frequency can be adjusted independently. Also, one can tune the filters electronically by varying the VDTA's bias currents. The proposed notch filter uses two capacitors, one resistor, and a VDTA. For effective notching of the 50Hz PLI and three consecutive odd harmonics (150Hz, 250Hz, and 350Hz), the comb filter's pole frequencies and quality factors are set to 50Hz, 150Hz, 250Hz, and 350Hz and 10, 20, 30, and 40, respectively. The filters have been simulated using PSPICE simulator software in 180nm CMOS technology. The simulated frequency responses of the proposed filters show the sharp notching of these frequencies. Further, to check the filter's effectiveness in the time domain, an ECG signal is corrupted with an artificial 50Hz PLI and passed through. The output response shows that the proposed filter effectively suppresses the noise from ECG signals.