SN RF - SNR Filter

(05/10/02)

PURPOSE

Create a low-pass Butterworth curve.   Example.

SEE ALSO

SN RB [SNR Butterworth]
TF SNR [Transfer Function - CTF correction, using frequency dependent SNR]

USAGE

.OPERATION: SN RF

.PASS AND STOP FREQUENCIES: 0.1,.2
[Pass and stop frequencies for Butterworth filter.]

.NUMBER OF POINTS: 128

.RANGE [0,1] THAT FSC IS MAPPED TO [FSCmin:FSCMax]: 0.1, 0.98

.FACTOR APPLIED ON FSC/(1-FSC): 2

.DOCUMENT FILE: snrf_doc
[Name of document file that will contain Butterworth filter.]

NOTES

  1. Create SNR curve from Butterworth FSC shape. The SSNR is equal to :
       SNR(f)= A FSC'/(1-FSC')
    Where 'A' is the factor (set to 2 in the previous example), FSC' is FSC mapped from [0,1] to [0.1,0.98] (in the previous example).
       FSC' = FSCMin + FSC (FSCMax-FSCMin)

  2. See 'TF SNR'.

  3. Implemented by L. JOYEUX

SUBROUTINES

SNRF

CALLER

UTIL4

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