A linear phase high pass filter having a linear phase low pass filter in parallel with an electronic delay means is disclosed to remove baseline wander from an ECG signal. The linear phase low pass filter is preferably a digital Infinite Impulse Response (IIR) filter. An input ECG signal is simultaneously presented to an IIR low pass filter and an electronic delay. The low pass filter passes the low frequency baseline signal while blocking the ECG signal comprised of higher frequency components than the cutoff frequency of the low pass filter. Thereafter, the outputs from the IIR low pass filter and delay are passed to a summer that subtracts the output of the low pass filter from the output of the delay to produce the output of the filter. The combination of the output of a low pass filter being subtracted from a delayed input signal produces a high pass filter. The resulting high pass filter has a -0.3 dB cutoff frequency of about 0.5 Hertz while providing a virtually constant group delay for the ECG signal passed through the filter.
展开▼
