This library was written during research on heart biosignals.

Most useful is probably the part with FIR filters, based on gnuradio's implementation of the Window Method for FIR Filter Design.

See hsh_signal/signal.py for methods (low-pass, high-pass, etc.) directly applicable to an array of evenly-sampled signal values, or hsh_signal/filter.py for block-connectable filters intended for real-time applications.

The file hsh_signal/alivecor.py implements a decoder for AliveCor's Kardia EKG (electrocardiograph). This device captures the raw electrical signal, which is then frequency-modulated onto an 18.8 kHz audio carrier that is transmitted to the microphone in a phone/tablet.

Demodulation of the audio signal can be achieved via a phase-locked loop, with subsequent low-pass filter to remove high-frequency electrical noise, and a band-reject filter to remove 50 Hz mains noise. Note that for the US, you may need to change this filter to 60 Hz.

-- David git@abanbytes.eu

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