> On Jan 6, 4:41 pm, jim <"sjedgingN0Sp"@m@mwt,net> wrote:
> > Laron wrote:
> >
> > > I just know there would be a lpf, not quite sure about the reconstruction
> > > process.
> > > I got an idea that the overshoot caused from the lpf, but the detail "how"
> > > is still not clear.
> >
> > A low pass filter with only positive values and a DC gain of 1 will
> > guarantee no overshoot.
> >
> > -jim
> But that is not interpolating.
And why would you say that?
Take his example of [1 0 1 1 0 1].
Stuff it with 0 so that it becomes
[1 0 0 0 1 0 1 0 0 0 1 0]
Low Pass Filter with [1/2 1 1/2]
and you get
[1 .5 0 .5 1 1 1 .5 0 .5 1]
In practice this will be done more efficiently by filtering the original with
[1/2 1/2] and interleaving the filtered result with the original sequence.
-jim
Reply by JCH●January 10, 20102010-01-10
"pnachtwey" <pnachtwey@gmail.com> schrieb im Newsbeitrag
news:4e8b1657-7e35-4630-9090-298b23d6b8ea@u7g2000yqm.googlegroups.com...
> On Jan 9, 1:55 am, "JCH" <ja...@nospam.arcornews.de> wrote:
>> "Laron" <jason.pi...@inbox.com> schrieb im
>> Newsbeitragnews:BOednfutGppmrtnWnZ2dnUVZ_uWdnZ2d@giganews.com...
>>
>> > Hi,
>> > When simulate the FIR filter response, run interp(Matrix,n) in
>> > matlab,
>> > the maximum of Matrix is 1,but the response is larger than 1?
>> > I wonder know why this could be happen and how to degrade this
>> > effect?
>>
>> You possibly have an ODE (system) of 2nd degree:
>>
>> See Page 1
>> *http://home.arcor.de/janch/janch/_control/20100109-overshooting/
>> 0,0001 u'' + 0,01 u' + u = w
>>
>> See Page 2: Degrading using higher damping
>> 0,0001 u'' + 0,018 u' + u = w
>>
>> --
>> Regards JCH
> This has nothing to do with the original question. Laron wants to
> know how to INTERPOLATE without OVERSHOOTING.
A 'possible' alternative explaination could be a bad DFT approximation
(Gibbs phenomenon). I don't like calling it interpolation in this context.
What you see here is approximation:
* http://home.arcor.de/janch/janch/_control/20100110-dft/
--
Regards JCH
Reply by pnachtwey●January 10, 20102010-01-10
On Jan 6, 4:41�pm, jim <"sjedgingN0Sp"@m@mwt,net> wrote:
> Laron wrote:
>
> > I just know there would be a lpf, not quite sure about the reconstruction
> > process.
> > I got an idea that the overshoot caused from the lpf, but the detail "how"
> > is still not clear.
>
> A low pass filter with only positive values and a DC gain of 1 will
> guarantee no overshoot.
>
> -jim
But that is not interpolating.
Peter Nachtwey
Reply by pnachtwey●January 10, 20102010-01-10
On Jan 9, 1:55�am, "JCH" <ja...@nospam.arcornews.de> wrote:
> "Laron" <jason.pi...@inbox.com> schrieb im Newsbeitragnews:BOednfutGppmrtnWnZ2dnUVZ_uWdnZ2d@giganews.com...
>
> > Hi,
> > � �When simulate the FIR filter response, run interp(Matrix,n) in matlab,
> > the maximum of Matrix is 1,but the response is larger than 1?
> > � �I wonder know why this could be happen and how to degrade this
> > effect?
>
> You possibly have an ODE (system) of 2nd degree:
>
> See Page 1
> *http://home.arcor.de/janch/janch/_control/20100109-overshooting/
> 0,0001 u'' + 0,01 u' + u = w
>
> See Page 2: Degrading using higher damping
> 0,0001 u'' + 0,018 u' + u = w
>
> --
> Regards JCH �
This has nothing to do with the original question. Laron wants to
know how to INTERPOLATE without OVERSHOOTING.
Peter Nachtwey
Reply by JCH●January 9, 20102010-01-09
"Laron" <jason.piker@inbox.com> schrieb im Newsbeitrag
news:BOednfutGppmrtnWnZ2dnUVZ_uWdnZ2d@giganews.com...
> Hi,
> When simulate the FIR filter response, run interp(Matrix,n) in matlab,
> the maximum of Matrix is 1,but the response is larger than 1?
> I wonder know why this could be happen and how to degrade this
> effect?
On Jan 5, 10:55�pm, "Laron" <jason.pi...@inbox.com> wrote:
> Hi,
> � � When simulate the FIR filter response, run interp(Matrix,n) in matlab,
> �the maximum of Matrix is 1,but the response is larger than 1?
> � � I wonder know why this could be happen and how to degrade this
> effect?
>
> B. R.
> Thanks.
You can use a Nth order polynomial to interpolate between points. A
3rd order polynomial will do or even a 3rd order cubic spline but the
trick it to ensure the derivative at the peaks is 0. Easy.
Peter Nachtwey
Reply by Jerry Avins●January 7, 20102010-01-07
Jim wrote:
>
> Jerry Avins wrote:
>> jim wrote:
>>
>> ...
>>
>>> it didn't sound like he was asking about reconstruction. He asked about
>>> interpolating without overshoot.
>> Interpolating is sort of partial reconstruction. If you interpolate the
>> signal 0, 1, 1, 0, -1, -1, ... by two, you get 0, .577, 1, 1.55, 1, 577,
>> 0. -.577, -1, -1.55, -1, -.577, ....
>>
>
>
> Surely you can't be claiming that is the only possible way to
> interpolate that sequence.
>
> What about linear interpolation? That would produce no overshoot. And
> the reason is the filter [1/2 1/2] has unity gain at DC and no negative
> terms. Any other filter that is also so constrained can be used for
> interpolation without any overshoot.
That's not the only way to interpolate it, but it is some of the points
that would appear in a reconstruction. In general, a good interpolation
has that characteristic.
Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
Reply by jim●January 7, 20102010-01-07
Jerry Avins wrote:
>
> jim wrote:
>
> ...
>
> > it didn't sound like he was asking about reconstruction. He asked about
> > interpolating without overshoot.
>
> Interpolating is sort of partial reconstruction. If you interpolate the
> signal 0, 1, 1, 0, -1, -1, ... by two, you get 0, .577, 1, 1.55, 1, 577,
> 0. -.577, -1, -1.55, -1, -.577, ....
>
Surely you can't be claiming that is the only possible way to
interpolate that sequence.
What about linear interpolation? That would produce no overshoot. And
the reason is the filter [1/2 1/2] has unity gain at DC and no negative
terms. Any other filter that is also so constrained can be used for
interpolation without any overshoot.
-jim
> ...
>
> Jerry
> --
> Engineering is the art of making what you want from things you can get.
> �����������������������������������������������������������������������
Reply by Jerry Avins●January 7, 20102010-01-07
jim wrote:
...
> it didn't sound like he was asking about reconstruction. He asked about
> interpolating without overshoot.
Interpolating is sort of partial reconstruction. If you interpolate the
signal 0, 1, 1, 0, -1, -1, ... by two, you get 0, .577, 1, 1.55, 1, 577,
0. -.577, -1, -1.55, -1, -.577, ....
...
Jerry
--
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������
Reply by glen herrmannsfeldt●January 6, 20102010-01-06
Laron <jason.piker@inbox.com> wrote:
(snip on overshoot and reconstruction)
> I just know there would be a lpf, not quite sure about the
> reconstruction process. I got an idea that the overshoot
> caused from the lpf, but the detail "how" is still not clear.
Because it is the right answer.
Another way to see it, take a square wave of amplitude one
and low pass filter it such that only the fundamental comes through.
The peak will be higher than 1.0. Mostly the third harmonic is
negative at the peak of the fundamental, so when you remove it the
result has a higher amplitude.
-- glen