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)