FIR

Description

A finite impulse response (FIR) filter is a filter whose impulse response (or response to any finite length input) is of finite duration, because it settles to zero in finite time.

The impulse response (that is, the output in response to a Kronecker delta input) of an Nth-order discrete-time FIR filter lasts exactly N + 1 samples (from first nonzero element through last nonzero element) before it then settles to zero. FIR filters can be discrete-time or continuous-time, and digital or analog.

Alternatively, FIR filters in obsinfo are also commonly documented using the Coefficients class, though FIR has the advantage of allowing representation of symmetric FIR coefficients without repeating them.

For a more detailed discussion, click here.

Python class:

FIR

YAML / JSON label:

FIR

Corresponding StationXML structure

FIR

Object Hierarchy

Superclass

Filter

Subclasses

None

Relationships

Is nested in Stage

Attributes

Name	Type	Required	Default	Equivalent StationXML	Remarks
symmetry	List of values: ODD, EVEN, NONE	Y	None	Symmetry
coefficients	List of numbers	N	None	NumeratorCoefficient
coefficient_divisor	number	N	1.0	NOT USED

JSON schema

https://www.gitlab.com/resif/smm/obsinfo/-/tree/master/obsinfo/data/schemas/filter.schema.json

Example

_templates/TEMPLATE.FIR.filter.yaml

---
format_version: "1.0"
revision:
   authors:
        - {$ref: "persons/EXAMPLE.person.yaml"} # Reference to person file,
                                                 # or fields of a person element
   date: "2024-09-30" # yyyy-mm-dd
filter:
   type: "FIR"
   symmetry: "NONE" # "EVEN", "ODD" or "NONE"
   coefficients:
       - 1
       - 10
       - -20
       - 30
       - -20
       - 10
       - 1
   delay.samples: 3   # used to calculate stage-level delay, should be at/before max peak
   # BEGIN OPTIONAL filter elements
   coefficient_divisor: 12  # number to divide all coefficients by for unity gain (1)
   # END OPTIONAL filter elements
# BEGIN OPTIONAL top-level elements
notes: 
   - ""
# END OPTIONAL top-level elements