SAC Command Reference Manual

FIR

SUMMARY

Applies a finite-impulse-response filter.

SYNTAX

FIR {REC|FFT},file

INPUT

FFT:Apply the FIR filter using the transform method.
REC:Apply the FIR filter recursively.
file:The name of the file containing the FIR filter.

ALTERNATE FORMS

DFT may be used in place of FFT.

DEFAULT VALUES

FIR FFT FIR

DESCRIPTION

The filter applied by this command must have been designed by using the DFIR interactive filter design program (see BUGS below). The filter is applied using the transform method unless you request the recursive method or the number of data points is too large for the transform method. These filters all have zero phase distortion but can produce precursors with impulsive signals.

HEADER CHANGES

DEPMIN, DEPMAX, DEPMEN

ERROR MESSAGES

  • 1301: No data files read in.
  • 1306: Illegal operation on unevenly spaced file
  • 1307: Illegal operation on spectral file
  • 1601: File and filter sampling intervals not equal for
    • The filter must be designed using the same sampling rate as the data to be filtered.
  • 1603: Inadequate memory to perform FIR filter.

WARNING MESSAGES

  • 1602: Inadequate memory to perform FIR filter using DFT.
    • the recursive method will be used automatically.

REFERENCES

See Chapter 3 of Rabiner and Gold, Theory and Application of Digital Signal Processing, Prentice-Hall, 1975 for a discussion of FIR filters.

LATEST REVISION

July 22, 1991 (Version 8.0)