ELECTROCARDIOGRAPH HAVING LARGE LOW FREQUENCY DYNAMIC RANGE

摘要

An ECG signal measuring system (40) uses low frequency compression/enhancement techniques combined with dither techniques to effectively increase the dynamic range, resolution is maintained without increasing the number of bits of the ADC (35). The HPF (42) receives an input signal (i.e., the bias current combined with ECG input signal) and attenuates the low frequency components of the input signal, including a portion of the frequency band within the desired ECG frequency band. The ADC (35) oversamples the output signal of the HPF (42). The DF (44) receives the output samples of the ADC (35) and generates output samples at rate that is at least twice the maximum frequency of the desired ECG output signal. The CF (46) amplifies the low frequency end of the DF (44) output samples. The gain and cutoff frequency of the CF (46) are set to offset the HPF's (42) attenuation of those low frequency components of the input signal below the minimum frequency of the desired ECG output signal. System noise can be used as the dither.