bugGNU Octave - Bugs: bug #38528, signal package: ellipord outputs...


bug #38528: signal package: ellipord outputs complex filter order for high-pass filter

Submitted by:  None
Submitted on:  Sat Mar 16 13:58:34 2013  
Category: Octave Forge PackageSeverity: 3 - Normal
Priority: 5 - NormalItem Group: Incorrect Result
Status: FixedAssigned to: None
Originator Name: Originator Email: -unavailable-
Open/Closed: ClosedRelease: dev
Operating System: Any

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Thu Jan 23 06:24:54 2014, comment #2:

This bug has been fixed, the fix will be part of the next signal package release.


Mike Miller <mtmiller>
Project Administrator
Sat Mar 16 18:11:21 2013, comment #1:

Confirmed, the current ellipord implementation assumes low-pass when the first two arguments are scalars.

Mike Miller <mtmiller>
Project Administrator
Sat Mar 16 13:58:34 2013, original submission:

When using the function ellipord to calculate the order of a high-pass* Cauer filter, it returns a complex number whereas the order of a filter should always be a real and positive integer. The following line reproduces the issue:

>> ellipord(0.955,0.945,1,20)

output: ans = 4 - 2i

Based on order calculations of bandpass filters and a lowpass filter with the same distance between the passband an the stopband, maximum passband attenuation and minimum stopband attenuation, an order of 3 or 4 is expected. A file with all calculated filters is attached.

*High-pass filter: a filter with only one passband edge and one stopband edge with the passband edge at a higher frequency than the stopband edge. In other words, all frequencies beneath the stopband edge are suppressed and all frequencies above the passband edge are preserved.



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Attach File(s):

Attached Files
file #27612:  reproduce_ellipord_bug.m added by None (1kB - text/x-objcsrc)


Depends on the following items: None found

Items that depend on this one: None found


Carbon-Copy List
  • -unavailable- added by mtmiller (Posted a comment)
  • -unavailable- added by None (Submitted the item)

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    Follow 7 latest changes.

    Date Changed By Updated Field Previous Value => Replaced By
    Thu Jan 23 06:24:54 2014mtmillerStatusConfirmed=>Fixed
    Sat Mar 16 18:11:21 2013mtmillerStatusNone=>Confirmed
      Operating SystemGNU/Linux=>Any
      SummaryFunction ellipord outputs complex filter order for high-pass filter=>signal package: ellipord outputs complex filter order for high-pass filter
    Sat Mar 16 13:58:34 2013NoneAttached File-=>Added reproduce_ellipord_bug.m, #27612

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