Hi again, The definition of "broadband" may vary with the discipline that you work in. For EMC the definition is that the "pulse repetition frequency (1/period) is less than the resolution bandwidth". While there may be harmonics of switching frequencies seeming as "narrowband" because the 1/t is far higher than the bandwidth, there is a probability that there will be much lower frequencies present if the power supply is feeding digital circuits. Unless the power supply has a very high reverse isolation, there will be a degree of "digital" signals on the power lines. If this is the case, then the results for those signals will be over-estimated by the spectrum analyser. Regards Tim
************************ Tim Haynes Electromagnetic Engineering Specialist SELEX Galileo, A Finmeccanica Company 300 Capability Green Luton LU1 3PG (Phone () +44 (0) 1582 886239 (Mob )) +44 (0) 7540629920 (Fax 7)+44 (0)1582 795863 (Email *) [email protected] www.selexgalileo.com P Please consider the environment before printing this email. There are 10 types of people in the world-those who understand binary and those who don't. J. Paxman ________________________________ From: Mike Violette [mailto:[email protected]] Sent: 18 June 2010 13:12 To: [email protected] Subject: Re: [PSES] Spectrum analyzers for MIL-STD-461 CE101? *** WARNING *** This message has originated outside your organisation, either from an external partner or the Global Internet. Keep this in mind if you answer this message. Hi Folks, For CE101, any measured signals *should* be narrowband, harmonics of the power line, notably. The RBW characteristics will be of nominal importance. We’ve used the 856X series and get good results. Mike Violette [email protected] Washington Laboratories Radio Frequency and Electrical Safety 301 216-1500 cell: 240 401 1388 ________________________________ From: Haynes, Tim (SELEX GALILEO, UK) [mailto:[email protected]] Sent: Friday, June 18, 2010 3:41 AM To: [email protected] Subject: Re: [PSES] Spectrum analyzers for MIL-STD-461 CE101? Hi All, As memory serves, the difference between a "6dB filter" with a 2:1 6/60dB shape factor and a "3dB Gaussian filter" is that the 3dB filter is 1.5 greater than the 6dB filter... So in terms of the broadband signal, the 3dB filter will read 20*log(1.5) higher - about 3.5dB. That is, if the spec an does not overload on the broadband signal... Regards Tim ************************ Tim Haynes Electromagnetic Engineering Specialist SELEX Galileo, A Finmeccanica Company 300 Capability Green Luton LU1 3PG (Phone *) +44 (0) 1582 886239 (Mob *) +44 (0) 7540629920 (Fax *)+44 (0)1582 795863 (Email *) [email protected] www.selexgalileo.com P Please consider the environment before printing this email. There are 10 types of people in the world-those who understand binary and those who don't. J. Paxman ________________________________ From: Ken Javor [mailto:[email protected]] Sent: 18 June 2010 03:37 To: [email protected] Subject: Re: [PSES] Spectrum analyzers for MIL-STD-461 CE101? *** WARNING *** This message has originated outside your organisation, either from an external partner or the Global Internet. Keep this in mind if you answer this message. There are a couple issues here, as I see it. If we are talking impulse BW, that means voltage is proportional to BW, and since power is proportional to the square of voltage, that means that impulsive power is proportional to the square of BW. Thermal, i.e., incoherent power is proportional to BW, which in turn means that the noise potential is proportional to square root BW. But there is another issue in comparing the response of filters to BB signals. That is the overall shape of the filters. Given identical shape factors, there is no doubt some relationship between 3 and 6 dB filter responses to BB signals. But in order to be able to calculate or predict that difference, you have to know the shape factor. One way manufacturer’s sometimes quantify that is by also specifying the 60 dB BW. If you also know that number, prediction within a dB ought to be possible. Somebody want to contact Werner Schaefer? He should be all over this one. Ken Javor Phone: (256) 650-5261 ________________________________ From: <[email protected]> List-Post: [email protected] List-Post: [email protected] List-Post: [email protected] Date: Thu, 17 Jun 2010 17:26:51 -0700 To: Ken Javor <[email protected]> Cc: <[email protected]> Subject: Re: [PSES] Spectrum analyzers for MIL-STD-461 CE101? Ken, wouldn't the level at the output of the 3dB filter be about 1dB greater than the 6dB filter, if signal is broadband compared the BW? Isn't energy related to sqrt of BW. _______________________________________ _____________________________________________ Ralph McDiarmid | Schneider Electric | Renewable Energies Business | CANADA | Compliance Engineer From: Ken Javor <[email protected]> To: [email protected] List-Post: [email protected] List-Post: [email protected] List-Post: [email protected] Date: 06/17/2010 05:22 PM Subject: Re: [PSES] Spectrum analyzers for MIL-STD-461 CE101? ________________________________ If memory serves, the difference between opt 462 IBW and 3 dB BW was a factor of 1.5. Meaning that the IBW rating of a filter originally spec'd at 3 dB points was 1.5 times the 3 dB BW. Now if you can get one of the forum members to apply an impulse generator to an EMI receiver with 6 dB BW spec'd, then you will have all the info you need to know. Ken Javor Phone: (256) 650-5261 > From: Ken Javor <[email protected]> > Date: Thu, 17 Jun 2010 19:15:48 -0500 > To: Untitled <[email protected]> > Conversation: Spectrum analyzers for MIL-STD-461 CE101? > Subject: Re: Spectrum analyzers for MIL-STD-461 CE101? > > There are all sorts of spectrum analyzers and receivers out there with > coverage to 30 Hz. Agilent and R&S readily come to mind. The HP 8566 Opt 462 > was impulse BWs, not 6 dB. > > The difference between 3 dB and 6 dB BW will only affect BB signals, like > rectification harmonics. If you know the shape factor of the 3 dB filter > (Gaussian for the 8566) vs. the 6 dB filter, you can calculate how much extra > signal the 3 dB BW machine would report over a 6 dB BW machine. > > Ken Javor > > Phone: (256) 650-5261 > > >> From: "[email protected]" <[email protected]> >> Date: Thu, 17 Jun 2010 16:58:19 -0700 >> To: <[email protected]> >> Subject: Spectrum analyzers for MIL-STD-461 CE101? >> >> Hi, >> >> I need to rent a spectrum analyzer for performing MIL-STD-461 CE101 tests. >> Although the requirements go down to 30Hz, I only need to start at 100Hz. >> >> After sifting out analyzers with frequency range limits, and those with >> -3dB IF bandwidth specifications, I keep coming back to the venerable HP >> 8566B or 8568A with option 462 (bandwidths spec'd at -6dB). >> >> 1) For those who perform this test, what spectrum analyzers do you use? >> 2) How much different will readings be if I used equipment with -3dB IF >> bandwidth specs? >> >> TIA, >> Pat Lawler >> EMC Engineer >> SL Power Electronics Corp. >> >> - >> ---------------------------------------------------------------- >> This message is from the IEEE Product Safety Engineering Society emc-pstc >> discussion list. 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