The reason for the 1.8 factor is that you are calibrating with a CW signal. When you switch the modulation on in real testing the peak level for the amplifier will be in the range of 1.8 of the CW level. It’s just a pre-caution not to overdrive the amplifier.
Best Regards Lothar Schmidt Director Regulatory & Antenna Services CETECOM Inc. 411 Dixon Landing Road Milpitas, CA 95035 Phone +1 (408) 586 6214 Fax +1 (408) 586 6299 email lothar.schm...@cetecomusa.com <mailto:lothar.schm...@cetecomusa.com> This e-mail may contain proprietary, privileged and confidential information for the sole use of the named intended recipient. Any review or distribution of this e-mail by any party other than the intended recipient or that person's agent is strictly prohibited. If you are not the intended recipient, please delete all copies and immediately contact the sender. You must not, directly or indirectly, use, disclose, distribute, print, or copy any part of this message if you are not the intended recipient. ________________________________ From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Bob Richards Sent: Tuesday, August 05, 2008 7:15 PM To: ieee Subject: Re: BS EN 61000-4-3:2006 Don, I agree completely with the additional checks that you perform. In my opinion, performing the calibration at 18v/m instead of 10v/m is not a good idea. I understand and agree with the intent, but in practice it can cause problems. In a chamber that does not perform well, you may be overdriving the amp at some probe positions (nulls) just trying to level to 18v/m. This can cause harmonics that can affect the probe readings and give erroneous field uniformity information. I have seen harmonics affect the probe readings when trying to calibrate below 80 MHz with bi-log type antennas, where the antenna factor really stinks at the lower frequencies. Even though the standard says what it says, I think it is better to calibrate at a lower level so as to make the harmonics a non-issue, make the calculations for the new drive levels (to include the 80% peak power) then perform the checks you describe. You also need to peform the radiated harmonics check as described in the standard. I would then feel much more comfortable defending the results. Bob Richards, NCT --- On Tue, 8/5/08, don_borow...@selinc.com <don_borow...@selinc.com> wrote: .... And the standard suggests doing field calibrations at the peak level of the RF during AM modulation, e.g., when calibrating for 10 V/m testing, calibrate the field at 18 V/m, which is the peak level of the RF with 80% AM modulation turned on (I have always favored this method). I do two additional checks not discussed in the standard: 1. I use the uniform drive level method of field calibration. After the calibration, I compare the drive level used during the calibration to that obtained from the 16-point calculation (for most points, the resultant drive from the 16-point calculation is lower than the uniform drive used for the field calibration); 2. Using the drive table obtained from the 16-point calculation, I make a power measurement at the output of the power amplifier to make sure the output power is comfortably within the maximum capability of the amplifier. - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.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 emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.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 emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
