>-----Original Message----- >From: Low, Aaron S [mailto:aaron.s....@lmco.com] >Sent: Wednesday, March 19, 2003 7:44 AM >To: emc-p...@majordomo.ieee.org >Subject: antenna port conducted emissions > > > >Folks, > >I am interested in your opinions regarding antenna port >conducted emissions >(MIL-STD-461D CE106) on a spread spectrum/frequency hopping device. > >Is it practical to automatically measure (using a swept scan >EMI receiver) >emissions from such a device? I would think that when using >spread spectrum >and a swept scan receiver, the receiver has some large probability of >missing the emissions caused by a particular harmonic when using swept >scanning systems. > >The limit for CE106 (transmitters) is derived from the power of the >fundamental (there is no fundamental, only a band of >operation), how do you >measure that power on the EMI receiver? > >Does anyone have any experience/advice they would be willing >to part with? > >Thanks >Aaron Low > >ps. I am relatively new to this field, so my question may >seem very basic >to many of you; please excuse me. > >
Aaron: First question is are you sure you should be working to 461D? 461E came out 20 August 1999. Now, to address your technical situation. Yes, you do have a fundamental. Just because it's hopping doesn't mean it's not there. Granted, 461 CE06 (later CE106) originated in the era of non-hopping systems, and may address them better in a future revision, but it does say that your reference will be the peak power level of the fundamental. You can measure the peak power by using a spectrum analyzer in peak hold, using sufficient bandwidth to ensure the detector actually charges to the peak during the time that the fundament dwells in the SA resolution bandwidth. Sometimes you can sweep a small portion of spectrum, or you can go to zero span width and just sit at some frequency waiting for the fundamental to hop there. You may find that the fundamental amplitude varies across the hopping range, so you might need to disable the hopping and fix the fundamental to one or more specific frequencies. Remember when looking for harmonic content, the hop sizes will be n x the fundamental hop size. Probabability of intercept is a problem, and I usually scan very slowly and do several overlaid sweeps of the spectrum. Many of the transmitters that I see have a short duty cycle (like 7 uS on and 993 uS in standby), so this makes the signal acquisition even more "challenging". Sometimes I set automated scans to run 16 hours overnight, or over a weekend. Regards, Ed Ed Price ed.pr...@cubic.com Electromagnetic Compatibility Lab Cubic Defense Systems San Diego, CA USA 858-505-2780 (Voice) 858-505-1583 (Fax) Military & Avionics EMC Is Our Specialty Shake-Bake-Shock - Metrology - Reliability Analysis This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
