US 4,243,045 AGranted

Method and apparatus for the suppression of interference signals in a useful signal

AssigneeSiemens Aktiengesellschaft

InventorMichael Maas

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Abstract

In an exemplary embodiment, the interference signals can occur as a mixture consisting of narrow interference pulse peaks of high amplitude and interference hum. It is desirable that such interference peaks and interference hum in a useful signal be suppressed without mutual influencing. To this end, an occurring useful signal having possibly superimposed interference signals is supplied to an interference hum filter. The filtered-out interference hum component is opposingly superimposed on the original signal for the purpose of compensation of the interference hum. This applies only for such a length of time as there are no interference pulse peaks recognized by a recognition installation. If such an interference pulse peak is recognized, the filter is disconnected from the input signal and switched over to self-oscillation operation. An artificial oscillation with an amplitude and frequency equal to that of the previously selected interference hum component is then generated without a phase jump and superimposed on the useful signal. The interference pulse peak is simultaneously blanked out. The exemplary embodiment can be particularly utilized in the case of electrocardiogram processing for the purpose of suppression of pacemaker pulses and power supply hum.

Claims17

Dependent claims

A method for suppressing noise signals in a useful signal, said method comprising the steps of:

(a) supplying an input signal comprising a useful signal (U1) which is subject to a noise hum signal (U.sub.N) and to noise in the form of narrow noise pulses (P) of high amplitude which may be superimposed on the noise hum signal (U.sub.N);
(b) monitoring said input signal to sense the presence of a narrow noise pulse (P);
(c) in the absence of the sensing of such a narrow noise pulse (P):
(c1) supplying the input signal to a noise hum filter (B1) to derive from the input signal a filtered-out interference hum component (U2) corresponding in waveform as a function of time to said noise hum signal (U.sub.N);
and
(c2) superimposing on the input signal in opposing relation said filtered-out interference hum component (U2) to tend to suppress the noise hum signal (U.sub.N);
and
(d) in the response to the sensing of such a narrow noise pulse (P) pursuant to step (b):
(d1) suppressing such narrow noise pulse;
(d2) decoupling the noise hum filter (B1) from the input signal, and switching over said noise hum filter (B1) to self-oscillation operation such that it continues to oscillate with the amplitude and frequency of the previously selected interference hum component without a phase jump to supply an artificially produced oscillation;
and
(d3) superimposing on the input signal said artificially produced oscillation for the purpose of compensation of the interference hum during the period of supression of said narrow noise pulse.

9 more elements

Apparatus for suppressing noise signals in a useful signal, said apparatus comprising:

(a) a measuring signal path having signal input means for supplying to the measuring signal path an input signal comprising a useful signal (U1) which is subject to a noise hum signal (U.sub.N) and to noise in the form of narrow noise pulses (P) of high amplitude which may be superimposed on the noise hum signal (U.sub.N), and having signal output means;
(b) monitoring means connected with said signal input means, and comprising an interference pulse peak recognition installation (B2) for monitoring the input signal to sense the presence of a narrow noise pulse (P);
(c) disconnect switch means (S1) connected with and controlled by said interference pulse peak recognition installation (B2) and maintained in a first condition thereby in the absence of the sensing of such a narrow noise pulse (P), but being shiftable to a second condition,
(c1) a noise hum filter (B1) operable for filtering out an interference hum component (U2) from the input signal, corresponding in waveform as a function of time to said noise hum signal (U.sub.N), having filter input means connected with said signal input means under the control of said disconnect switch means (S1) such that in the absence of sensing of a narrow noise pulse (P) the disconnect switch means (S1) is in said first condition and supplies the input signal to said noise hum filter (B1) so that said noise hum filter (B1) derives from the input signal a filtered-out interference hum component (U2) corresponding in waveform as a function of time to said noise hum signal (U.sub.N);
(c2) said noise hum filter (B1) having filter output means connected with said measuring signal path for superimposing on the input signal in opposing relation said filtered-out interference hum component (U2) to tend to suppress the noise hum signal (U.sub.N),
(d) said interference pulse peak recognition installation (B2) being responsive to sensing of a narrow noise pulse (P) to actuate said disconnect switch means (S1) to said second condition,
(d1) said interference pulse peak recognition installation (B2) having output means connected with said measuring signal path for suppressing a narrow noise pulse at said signal output means in response to sensing of such narrow noise pulse by said interference pulse peak recognition installation (B2) pursuant to the monitoring of said input signal,
(d2) said disconnect switch means (S1) in said second condition decoupling the noise hum filter (B1) from said signal input means, and said noise hum filter (B1) having switchover means connected with and controlled by said interference pulse peak recognition installation (B2) and responsive to the sensing of a narrow noise pulse thereby to switch over said noise hum filter (B1) to self-oscillation operation such that it continues to oscillate with the amplitude and frequency of the previously selected interference hum component (U2) without a phase jump to supply an artificially produced oscillation;
and
(d3) said filter output means of said noise hum filter (B1) during the suppression of a narrow noise pulse superimposing on the input signal said artificially produced oscillation for the purpose of compensation of the interference hum during the period of suppression of said narrow noise pulse.

7 more elements

Dependencies are inferred from the claim text.