Atmapuri wrote:> Hi! > > >>What is the ratio of the signal bandwidth to the carrier frequency? > > > No carrier. Entire spectrum (from 0 to FS/2) was raising and falling > with time. I was interested in the envelope.If there is no carrier, what is being modulated? It seems to me (if I understand you right) that your signal is passing through a channel with varying gain, like the output of a radio would be if the volume control were constantly being varied. If that's the case, then every frequency component of the unvaried-amplitude signal has sidebands at the changing volume frequency(s).>>still be an envelope, but not the same envelope. What is often referred to >>as single sideband is in fact single sideband, suppressed carrier -- >>SSSC. Then there is no envelope at all with a single modulating frequency. >>We are left with M*A*[cos((wc + wm)*t)]. >> >>The modulation is there, but not the envelope. That's one reason the >>distinction is not merely semantic. > > > Humm. I think I had SSSC, but there was also the envelope. This > is because you think of modulation in terms of creating it, and not > recording it as a real world signal.Modulation is a process that impresses a signal on a carrier. AM, SSSB, and PM and its cousin FM are all examples. Both AM and SSSB have envelopes when the modulating signal is not a single frequency, but only AM's envelope is an image of the modulating signal. FM and PM have no envelopes. You don't store envelopes, only modulating and demodulated signals, or the entire modulated signal.> If you take a hammer and > beat with it on a plate, how do you determine the frequency of > the beating by using an accelerometer? When the hammer hits > you get a very wide band signal and the frequency of the beating > is a very low frequency.The repetition rate is the beating frequency. For many purposes, the spectrum produced by the plate is irrelevant.>>>>>What is polarity? (not an electrical engineer). >>>> >>>>The envelope has both negative and positive parts; an AM envelope is >>>>symmetrical about the time axis -- there are two curves. The demodulated >>>>signal is either the all-positive or all-negative part. >>> >>> >>>Humm... But abs(analytical signal) gives only one part. >> >>The magnitude of the analytic signal is sqrt(re^2 + im^2). What would abs >>mean here? > > > Absolute value = sqrt(re^2 + im^2) for complex numbers.That is also the magnitude of a complex number. One reason we bother to make an analytic signal with a Hilbert transforms is to be able to find its magnitude. An analytic signal is conveniently represented by a complex number.> Thanks!You're still welcome, but I think you ought to get a book, or at least look up the exact meanings of some of the terms you use. At least one of us is hampered by misconceptions. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
FIR Hilbert transformers
Started by ●January 4, 2006
Reply by ●January 9, 20062006-01-09
Reply by ●January 9, 20062006-01-09
Hi!> You're still welcome, but I think you ought to get a book, or at least > look up the exact meanings of some of the terms you use.There is nothing like a good book recommendation. (or several of them). I have pretty much all the standard DSP books, but many times I discover that people that wrote them assume that the reader knows everything about the analog logic and systems that the DSP builds upon. (because DSP is just another level to the analog EE systems). Thanks! Atmapuri
Reply by ●January 10, 20062006-01-10
Atmapuri wrote:> Hi! > > >>You're still welcome, but I think you ought to get a book, or at least >>look up the exact meanings of some of the terms you use. > > > There is nothing like a good book recommendation. > (or several of them). I have pretty much all the standard > DSP books, but many times I discover that people that wrote > them assume that the reader knows everything about the > analog logic and systems that the DSP builds upon. > (because DSP is just another level to the analog EE systems). > > Thanks! > AtmapuriThe ARRL handbook is an excellent compendium that outlines the essences of major branches of basic communications approaches. It is updated every year. I buy a new one every so often. http://www.arrl.org/catalog/?item=NO-HB2006 Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●January 11, 20062006-01-11
On 7 Jan 2006 05:21:21 -0800, "Rune Allnor" <allnor@tele.ntnu.no> wrote:> >Rick Lyons wrote: >> Hi Rune, >> >> I haven't followed all the details of this thread, >> but if Paul's modulated signal is low frequency >> relative to the signal sample rate (Fs), then perhaps >> the "absolute value followed by low pass filtering" >> scheme will work OK for him. > >I remember you mentioned that somebody had submitted >a Hilbert transformer for very low reltive frequencies to >your column in Signal Processing Magazine. > >Did that article ever get published? > >RuneHi Rune, no it didn't. Rune, I'll send ya' a private E-mail with more info on this subject. Regards, [-Rick-]
