Patent ID: 7684853

Claim:
An apparatus for suppressing power frequency common mode interference and used in a bioelectrical signal measuring system, comprising: a common mode interference signal extracting circuit; a driving circuit connected to the extracting circuit, the driving circuit configured to generate a first driving signal; and a delayer connected to the driving circuit, the delayer configured to perform a corresponding adjustable time delay on the first driving signal outputted by the driving circuit, wherein the driving circuit is further configured to change a phase of a common mode interference signal and amplify the common mode interference signal to generate, the first driving signal, wherein either the first driving signal or a second driving signal comprising a modified version of the first driving signal is selectively outputted to a living body on examination, wherein the apparatus further includes phase compensating and processing circuitry configured to: receive both a bioelectrical signal from the living body on examination and the first driving signal outputted from the driving circuit, determine a phase compensation amount of the first driving signal outputted from the driving circuit according to a characteristic value of a power frequency interference in the bioelectrical signal so as to phase-compensate the first driving signal outputted from the driving circuit to generate the second driving signal, and selectively output, based on a user selection, either the first driving signal or the second driving signal to the living body on examination.