class sdr.FIR

Implements a finite impulse response (FIR) filter.

This class is a wrapper for the scipy.signal.convolve() function. It supports one-time filtering and streamed filtering.

Notes

A FIR filter is defined by its feedforward coefficients \(h_i\).

\[y[n] = \sum_{i=0}^{N} h_i x[n-i] .\]

The transfer function of the filter is

\[H(z) = \sum\limits_{i=0}^{N} h_i z^{-i} .\]

Examples

See the FIR filters example.

Constructors

FIR(h: ArrayLike, streaming: bool = False)

Creates a FIR filter with feedforward coefficients \(h_i\).

Special methods

__call__(x: ArrayLike, ...) → NDArray

Filters the input signal \(x[n]\) with the FIR filter.

__len__() → int

Returns the filter length \(N + 1\).

String representation

__repr__() → str

Returns a code-styled string representation of the object.

__str__() → str

Returns a human-readable string representation of the object.

Streaming mode only

reset()

Resets the filter state. Only useful when using streaming mode.

flush() → NDArray

Flushes the filter state by passing zeros through the filter. Only useful when using streaming mode.

property streaming : bool

Indicates whether the filter is in streaming mode.

property state : NDArray

The filter state consisting of the previous \(N\) inputs.

Methods

impulse_response(N: int | None = None) → NDArray

Returns the impulse response \(h[n]\) of the FIR filter. The impulse response \(h[n]\) is the filter output when the input is an impulse \(\delta[n]\).

step_response(N: int | None = None) → NDArray

Returns the step response \(s[n]\) of the FIR filter. The step response \(s[n]\) is the filter output when the input is a unit step \(u[n]\).

frequency_response(...) → tuple[NDArray, NDArray]

Returns the frequency response \(H(\omega)\) of the FIR filter.

frequency_response_log(...) → tuple[NDArray, NDArray]

Returns the frequency response \(H(\omega)\) of the FIR filter on a logarithmic frequency axis.

Properties

property taps : NDArray

The feedforward taps \(h_i\) for \(i = 0,...,N\).

property order : int

The order of the FIR filter \(N\).

property delay : int

The delay of the FIR filter \(d = \lfloor \frac{N + 1}{2} \rfloor\) in samples.