Signal detector

Claim 1

A signal detector for detecting a biosignal with nearly known morphology in a disturbed input signal (ECG) having signal complexes, comprising: a detector input for detecting the input signal (ECG) with signal complexes and a detector output for emitting a detection signal that indicates the detection of the biosignal in the input signal; a threshold value discriminator connected with the detector input, said threshold value discriminator comparing the input signal (ECG) with a detection threshold value and outputting to the detector output a high level signal so that the detector output emits the detection signal if the threshold value is exceeded by the input signal; an amplitude detection device connected to the detector input and to the output of the threshold value discriminator and functions to detect a maximum amplitude of the detected signal complex during a predetermined time window, following the output of the detection signal; an amplitude memory for storing the maximum amplitude of the detected signal complex, said amplitude memory being connected to the amplitude detection device and having several storage elements for storing a plurality of amplitudes of preceding signal complexes; an arithmetic unit for calculating a variable lower limit value for the detection threshold value in dependence on the stored amplitudes, said arithmetic unit being connected to said amplitude memory and calculating the variable lower limit by giving a greater weight to the amplitudes of immediately preceding signal complexes than to amplitudes of older signal complexes; a detector parameter pre-selection circuit that is connected to the arithmetic unit and to the threshold value discriminator, said detector parameter pre-selection circuit determining an initial value for a detector parameter which reflects the sensitivity of the signal detector, the detector parameter determines the detection threshold value by responding to the detection signal and in dependence on the maximum amplitude; a detector parameter timing circuit connected to the threshold value discriminator for adjusting a predetermined time dependence of the detector parameter and thus also the detection threshold value, said detector parameter timing circuit starts with the initial value of the detector parameter, wherein the predetermined time dependence comprises in a first time domain a step-by-step reduction of the detection threshold value up to at most the lower limit value determined by the arithmetic unit.