Universal notch filter

Inventors

Drakulic, Budimir S. • FAKHAR, Sina • Foxall, Thomas G. • VLAJINIC, Branislav

Assignees

Streamex Corp

Abstract

Systems, methods, and computer program product embodiments are disclosed for removing any fixed frequency interfering signal from an input signal without introducing artifacts that are not part of the original signal of interest. An embodiment operates by using a virtual buffer with a length that matches a length of one cycle of an interfering signal. The embodiment extracts the interfering signal into the virtual buffer. For a sample in the next cycle of the interfering signal that corresponds to a virtual memory location for the virtual buffer, the embodiment can update one or more physical memory locations of the virtual buffer that are in the vicinity of the virtual memory location. This use of virtual buffer can remove any interfering signal without creating the artifacts associated with conventional notch filters.

Core Innovation

The disclosed invention provides a universal notch filter for filtering an input signal having an interfering signal, including a fixed-frequency interfering signal and its harmonics. The method uses quiet periods in the input signal to avoid artifacts and remove the interfering signal without introducing transient responses in the filtered signal.

During quiet periods, samples of the interfering signal are stored in virtual memory locations of a virtual buffer. The filtering is performed by subtracting the stored samples from a single cycle of the interfering signal in the virtual buffer to create a filtered signal, and the determining, storing, and subtracting are repeated to refine the filtered signal.

The virtual buffer supports non-integer cycle alignment by mapping virtual memory locations to physical memory locations via interpolation and averaging, including exponential averaging. Real-time tracking is achieved by computing the interfering frequency and adjusting the virtual buffer length so that it corresponds to one cycle of the interfering frequency, with quiet-period detection based on a non-quiet characteristic such as slope, magnitude, or signal power compared to a threshold.

Claims Coverage

The document provides three independent claims covering a computer implemented method, a universal notch filter apparatus, and a non-transitory computer-readable device. Across these independent claims, the core inventive concept comprises quiet-period detection, storing interfering-signal samples in a virtual buffer, subtracting samples from a single interfering-signal cycle to produce a filtered signal without transient responses, and repeating the process to refine the filtered signal.

All independent claims focus on quiet-period detection, capturing interfering-signal samples into virtual buffer virtual memory locations, subtracting those samples corresponding to a single interfering-signal cycle to remove the interfering signal without introducing transient responses, and repeating the determine, store, and subtract operations to refine the filtered signal.

Stated Advantages

Documented Applications