If you want to somewhat retain a square looking wave and non-sinusoidal, then you must keep the third harmonic. The first and third are essential. All subsequent odd harmonics can be filtered aggressively, i.e. w/ a multi-pole filter. The even harmonics add and subtract at the wrong places. You should not have the 2nd harmonic as it will distort the waveform substantially. Design your filter to begin just above the 3rd harmonic.
--- [email protected] wrote: > > > Hi All, > > My understanding of the harmonics has been: first > harmonic is fundamental > times one, second harmonic is fundamental times two, > third harmonic is > fundamental times three, and so on. This is how I > have seen it described > in books also. I do not remember any recent book > that provides this type > of information. > > During our filter design class, we were normally > asked to filter third > harmonic properly, as this was generally most > significant after the > fundamental. In a square wave with 50% duty cycle, > the even harmonics will > generally be non-existent (2nd, 4th, etc.). > > Regards, Ravinder > > Email: [email protected] > *************************************************************************** > Always do right. This will gratify some people and > astonish the rest. > .... Mark Twain > > > > > [email protected] (Scott Douglas) on 04/21/99 > 10:38:17 AM > > Please respond to [email protected] (Scott Douglas) > > To: [email protected] > cc: (bcc: Ravinder Ajmani/San Jose/IBM) > Subject: Harmonics > > > > > > Hi All, > > Recently an interesting discussion came up about > harmonics. A general > disagreement followed. We hope you all can offer > some insight and perhaps > help us settle the question. > > The question is numbering of harmonics. > > One side says that given a fundamental frequency of > 200 MHz, the first > harmonic is 400 MHz, the second harmonic is 600 MHz > and the third harmonic > is 800 MHz. > > The other side says that given a fundamental > frequency of 200 MHz, the > first harmonic is 200 MHz (or same as fundamental), > the second harmonic is > 400 MHz and the third harmonic is 600 MHz. > > The other part of the discussion revolved around > even and odd harmonics. > > One side says that even harmonics are lower > amplitude than the odd > harmonics, the other side says odd harmonics are > lower amplitude than even > harmonics. > > All discussions assumed non-sinusoidal sources, > generally our sources are > square- or modified-square waves. > === Best Regards Hans Mellberg EMC Consultant _________________________________________________________ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
