Coherent noise cancelling filter
AssigneeNewmont Mining Corporation
InventorGeorge H. McLaughlin
Life of this patent
Estimating the term…
Abstract
Apparatus and method for removing coherent noise from an electrical signal, such as powerline noise, and operating in real time. An operational amplifier with digital filter and a low pass filter in the feedback loop, with the digital filter providing a feedback signal corresponding to the coherent noise in the absence of the desired signal. In the preferred embodiment, an integrating type digital filter with digital memory, and alternative embodiments with condenser memory.
Claims29
In a coherent noise cancelling filter, the combination of:
- means defining a circuit input and a circuit output;
- an operational amplifier connected between said circuit input and circuit output;
- a feedback circuit connected from the output of said operational amplifier to the input thereof, said feedback circuit including a digital filter and a low pass filter connected in series between said operational amplifier output and input, said digital filter including memory means and first switching means for connecting said operational amplifier to said memory means;
- and
- timing means for operating said first switching means to interconnect said operational amplifier output and said memory means during a predetermined time.
A process for cancelling coherent noise in a signal which has an information period and a no information period, said noise havng a fundamental frequency and harmonics thereof, including the steps of:
- during a no information period, storing the signal, including the noise fundamental and lower harmonics, in memory;
- and
- during a subsequent information period, combining the stored signal with the then existing signal in cancelling relation providing the desired output signal.
Dependencies are inferred from the claim text.