Hi, I'm having to work through a bunch of waveform questions and a few have them really have me stumped. I'd appreciate if anybody can give me the help I need to answer the following questions: 1. State what parameters of the harmonic content need to have a precise values in order to generate a particular periodic waveform. 2. State what can limit the accuracy of a fourier series approximation to a periodic unsampled waveform. 3. State what can affect the shape of a waveform after sampling and then smoothing to a continous waveform. I'd really appreciate any pointers. Thanks guys.
Struggling with waveform questions.
Started by ●December 11, 2004
Reply by ●December 11, 20042004-12-11
mikelar10@yahoo.co.uk (Michael) writes:> Hi, > > I'm having to work through a bunch of waveform questions and a few > have them really have me stumped. I'd appreciate if anybody can give > me the help I need to answer the following questions: > > 1. State what parameters of the harmonic content need to have a > precise values in order to generate a particular periodic waveform.Ya' got me.> 2. State what can limit the accuracy of a fourier series approximation > to a periodic unsampled waveform.Look up/reread the Dirichlet conditions.> 3. State what can affect the shape of a waveform after sampling and > then smoothing to a continous waveform.What's the first thing one does when converting an analog signal to digital? -- Randy Yates Sony Ericsson Mobile Communications Research Triangle Park, NC, USA randy.yates@sonyericsson.com, 919-472-1124
Reply by ●December 11, 20042004-12-11
Randy Yates <randy.yates@sonyericsson.com> writes:> mikelar10@yahoo.co.uk (Michael) writes: > > > Hi, > > > > I'm having to work through a bunch of waveform questions and a few > > have them really have me stumped. I'd appreciate if anybody can give > > me the help I need to answer the following questions: > > > > 1. State what parameters of the harmonic content need to have a > > precise values in order to generate a particular periodic waveform. > > Ya' got me.I think I get what they're after here now: Is the Fourier series simply the magnitude of the harmonics? (Hint: No.) -- Randy Yates Sony Ericsson Mobile Communications Research Triangle Park, NC, USA randy.yates@sonyericsson.com, 919-472-1124
Reply by ●December 11, 20042004-12-11
Michael wrote:> Hi, > > I'm having to work through a bunch of waveform questions and a few > have them really have me stumped. I'd appreciate if anybody can give > me the help I need to answer the following questions: > > 1. State what parameters of the harmonic content need to have a > precise values in order to generate a particular periodic waveform.I think that question is poorly worded. Maybe putting it differently will help. How are the components necessarily related in a periodic waveform that has more than one frequency?> 2. State what can limit the accuracy of a fourier series approximation > to a periodic unsampled waveform. > > 3. State what can affect the shape of a waveform after sampling and > then smoothing to a continous waveform.That's another poorly worded question. I don't know what it's intended to mean, but it it might mean lots i=of things. Try this: You sample a waveform (presumably respecting the bandwith requirements) and then reconstruct it. So now you have this continuous signal and the question is, what can affect its shape? How about an analog filter, or a rectifier, or ...? Dollars to donuts, that's not the answer the prof wants, but it's a valid answer to the question he asked. You can't very well tell him to learn to express himself in English or find another profession, but you might be able to show him this reply.> I'd really appreciate any pointers. > Thanks guys.You have my sympathy. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●December 11, 20042004-12-11
Michael wrote:> > Hi, > > I'm having to work through a bunch of waveform questions and a few > have them really have me stumped. I'd appreciate if anybody can give > me the help I need to answer the following questions:I hope this isn't homework :-).> 1. State what parameters of the harmonic content need to have a > precise values in order to generate a particular periodic waveform.For each harmonic you need to specify its amplitude and its phase relationship to the zeroth harmonic.> 2. State what can limit the accuracy of a fourier series approximation > to a periodic unsampled waveform.Assuming that both time and amplitude are continuous (ie not discrete), then for a truely periodic waveform the fourier series is an exact representation. However, the Fourier series is usually an infinite sum and if this infinite sum is truncated, then the truncated Fourier series is only an approximation.> 3. State what can affect the shape of a waveform after sampling and > then smoothing to a continous waveform.Sampling should limit the bandwidth of the waveform before the sampling takes place. Limiting the bandwith with a low pass filter can change the shap of the waveform. I don't know what you mean by smoothing in this context. Erik -- +-----------------------------------------------------------+ Erik de Castro Lopo nospam@mega-nerd.com (Yes it's valid) +-----------------------------------------------------------+ "Open source is an intellectual-property destroyer. I can't imagine something that could be worse than this for the software business and the intellectual-property business." -- Jim Allchin, Microsoft
Reply by ●December 12, 20042004-12-12
Erik, a nit below: Fred "Erik de Castro Lopo" <nospam@mega-nerd.com> wrote in message news:41BBB2DD.749CF480@mega-nerd.com...> Michael wrote: >> >> Hi, >> >> I'm having to work through a bunch of waveform questions and a few >> have them really have me stumped. I'd appreciate if anybody can give >> me the help I need to answer the following questions: > > I hope this isn't homework :-). > >> 1. State what parameters of the harmonic content need to have a >> precise values in order to generate a particular periodic waveform. > > For each harmonic you need to specify its amplitude and its phase > relationship > to the zeroth harmonic.***The zeroeth harmonic doesn't have phase. The first harmonic does though.... and establishes where time=0 must be relative to the first harmonic and, thereby, the others.
Reply by ●December 12, 20042004-12-12
Fred wrote: ] ***The zeroeth harmonic doesn't have phase. The first harmonic does ] though.... and establishes where time=0 must be relative to the first ] harmonic and, thereby, the others. Are you saying that the fundamental (= zeroth (sp?) harmonic) doesn't have phase? That doesn't sound right to me... but it's too late at night for coherent thought. Ciao, Peter K.
Reply by ●December 12, 20042004-12-12
Peter K. wrote:> Fred wrote: > > ] ***The zeroeth harmonic doesn't have phase. The first harmonic does > ] though.... and establishes where time=0 must be relative to the first > > ] harmonic and, thereby, the others. > > Are you saying that the fundamental (= zeroth (sp?) harmonic) doesn't > have phase? > > That doesn't sound right to me... but it's too late at night for > coherent thought. > > Ciao, > > Peter K.If the second harmonic is an octave higher than the fundamental, doesn't that define the fundamental as the first harmonic and DC as the zeroth? DC has no phase. I'm with Fred. :-) Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●December 13, 20042004-12-13
On 2004-12-13 00:52:51 +0100, "Fred Marshall" <fmarshallx@remove_the_x.acm.org> said:> ***The zeroeth harmonic doesn't have phase. The first harmonic does > though.... and establishes where time=0 must be relative to the first > harmonic and, thereby, the others.The first harmonic is the fundamental (= the zeroth overtone). It does have a phase, as does the zeroth harmonic (DC) itself. It's just that for DC phase is a constant because it has zero frequency... -- Stephan M. Bernsee http://www.dspdimension.com
Reply by ●December 13, 20042004-12-13
