John, You are correct in noting that the current proposal for limits above 1 GHz in CISPR 22 uses a peak detector, rather than the average detector called out in the FCC Rules. This has been a major issue in the US CISPR G TAG. While we have gotten other items fixed, we have been unable to get movement on the issue of what detector to use. The FCC Rules do call out a peak detector limit above 1 GHz which is 20 dB above the stated limit for an average detector. Thus, the peak detector limit for class B equipment is about 74 dBuV/m @ 3 meters. The CISPR 22 proposed limit will be 50 dBuV/m @ 3 meters with a peak detector, 24 dB more stringent than the FCC limits (for an apples to apples comparison). There will be a relaxed limit of 70 dBuV/m for 3 years while test methods are evaluated and the limits are evaluated for adequate protection of radio services between 1 and 2.7 GHz. If you have contacts in companies in other member countries of CISPR, you might try getting them to lobby their national committees to vote NO on the upcoming FDIS (Final Draft International Standard), or if they vote YES, to vote to keep the limit at 70 dBuV/m when that decision comes up in a few years.
One other point on the proposed CISPR 22 limits - there is no difference between class A and class B above 1 GHz. The mainframe folks are going to get nailed just as bad as the PC manufacturers on this one. A technique that can be used to simulate an average detector with a spectrum analyzer is to set the resolution bandwidth to the specified value (1 MHz in this case) and then narrow the video bandwidth until no change is seen in the indicated value. This is slow and labor intensive unless you write a program to do it automatically. There are now receivers on the market that have average detectors and go to 40 GHz that you may wish to check out. They do cost more (2X), but should be much faster to use. Hope this helps. Good luck. Ghery S. Pettit Intel Corporation Note - opinions expressed are mine and not necessarily those of Intel. > -----Original Message----- > From: John Cronin [SMTP:[email protected]] > Sent: Wednesday, September 08, 1999 1:37 AM > To: [email protected] > Subject: Average Measurements above 1 GHz > > > I recently put out a question on measurements above I GHz. I got several > replies for which many thanks. > > The recommendations were to try several suppliers for pre-amps. These > included HP 8449, Miteq (low noise amps) and TEC in Mountain View. > > We actually used two Mini Circuits preamps in series which have enabled us > > to gain the necessary gain and noise figure. > > Now that we can carry out measurements at 3m I have another question. How > > to perform average measurements above 1 GHz. > > Most analyzers do not appear to have a specific CISPR compliant average > function. So how is the average measurement carried out? > > Use of the average detector could yield a few dB lower levels even for a > narrowband emission. > > As a point of information I note that the proposal for CISPR 22 > measurements > above 1 GHz does not allow the use of an average detector. This could > pose > eventual problems for manufacturers as it represents a considerable > tightening on the current FCC limits. > > I would be most grateful for any information on carrying out compliant > average measurements. > > Regards > > John Cronin > > > > ______________________________________________________ > Get Your Private, Free Email at http://www.hotmail.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). > --------- 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).
