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 16 Mar 2013 01:58:34 PM UTC  
Category:  Octave Forge Package Severity:  3 - Normal
Priority:  5 - Normal Item Group:  Incorrect Result
Status:  Fixed Assigned to:  None
Originator Name:  Originator Email:  -email is unavailable-
Open/Closed:  Closed Release:  dev
Operating System:  Any

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

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


Mike Miller <mtmiller>
Project Administrator
Sat 16 Mar 2013 06:11:21 PM UTC, comment #1:

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

Mike Miller <mtmiller>
Project Administrator
Sat 16 Mar 2013 01:58:34 PM UTC, 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 Files:

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


Depends on the following items: None found

Items that depend on this one: None found


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  • -email is unavailable- added by mtmiller (Posted a comment)
  • -email is unavailable- added by None (Submitted the item)

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    Follow 7 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2014-01-23 mtmiller StatusConfirmed => Fixed
        Open/ClosedOpen => Closed
    2013-03-16 mtmiller StatusNone => Confirmed
        Release3.2.4 => dev
        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
    2013-03-16 None Attached File- => Added reproduce_ellipord_bug.m, #27612

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