Field Guide · term

Also known as: digital filter

A digital filter passes some frequencies and attenuates others by performing arithmetic on a stream of samples — no physical components.1 The main families are FIR (finite impulse response) and IIR (infinite impulse response).

passband rejectedrejected frequency →
A digital filter passes a chosen band of frequencies and attenuates the rest — isolating one channel.

How it works

A low-pass filter keeps frequencies below a cutoff; a band-pass keeps a chosen range. In an SDR a narrow channel filter isolates one signal from a wide capture, often paired with decimation.

Relevance to SDR

Filtering is fundamental to channelising the IQ stream and to pulse shaping; specialised forms include the CIC, root-raised-cosine, and matched filters.

Sources

  1. Digital filter — Wikipedia, on FIR/IIR families and frequency response. ↩

See also

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