In message <[email protected]>, dated Mon, 31 Aug 2009, Mark Briggs <[email protected]> writes:
>Perhaps it is because there are multiple carriers, each of which is >changing at the symbol rate, we end up with a time-domain waveform that >has the potential to change at a rate much faster than the actual >symbol rate if there is any timing delay between the individual carriers? There are bound to be asynchronous transitions, because the carriers have different frequencies. This subject is a replay of one from about 60 years ago, originally about simple DSB AM, leading to articles like 'Are sidebands real?', and techniques that attempted to 'prove' that they are not. The general idea was to have very high RF selectivity and restore the audio frequency response by audio frequency means. This is the same technology as that used by the Dong with the Luminous Nose. (;-) The same controversy centred on frequency modulation, where the RF bandwidth requirements are VERY counter-intuitive unless the modulation index is near 1. The bandwidth is theoretically infinite, but much can be cut off without noticeably distorting the modulation. With modern modulation methods, it can be very difficult indeed to visualize what the true RF bandwidth is, and the only safe way is to search out published papers that present the results. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk Things can always get better. But that's not the only option. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
