http://www.ieee-pses.org/symposium http://www.emc2004.org/
Hi George, There is a specification for mobile phones EN 301 489-7 (you need also the general standard EN 301 489-1) which describes the measurement of the demodulated 1 kHz tone in the audio system of a cellular phone. This includes how to measure it and how to calibrate the audio part. The measurements are done measuring the sound pressure level. We use an audio analyzer with different type of filters specific for the 1 kHz. You can download the standard from the http://www.etsi.org/getastandard/home.htm it is free if you register with your email address. If you need more information contact me offline. Lothar Schmidt Technical Manager EMC, SAR, Antenna testing and BQB CETECOM Inc. 411 Dixon Landing Road Milpitas, CA 95035 Phone +1 408 586 6214 Fax +1 408 586 6299 From: [email protected] [mailto:[email protected]] On Behalf Of Price, Ed Sent: Tuesday, August 10, 2004 10:09 AM To: [email protected] Subject: RE: Selective Frequency Power Meter http://www.ieee-pses.org/symposium http://www.emc2004.org/ From: George Bittar [mailto:[email protected]] Sent: Tuesday, August 10, 2004 4:39 AM To: [email protected]; [email protected] Subject: Re: Selective Frequency Power Meter http://www.ieee-pses.org/symposium http://www.emc2004.org/ Actually, I am not trying to measure de carrier, but the 1KHz modulated AM at 80% signal! So, I have to measure selectively the 1KHz signal at the terminals of the equipment in order to know if the equipment is DEMODULATING the signal. The power level of 1KHz signal cannot be higher than -40dBm for my application. I have to mesure the behavior of this signal and trace it against the carrier, which goes from 150KHz to 80MHz for 61000-4-6 and 80MHz to 1GHz;1.4GHz to 2GHz for -4-3, and I'm sure you all know that! :-) Is it clear now? The point is not the signal I am generating, but the signal I am demodulating. Regards George George: It's best to assume that I know very little. Your problem seems to have changed from measuring RF power of an immunity signal to measuring the response of the EUT. You describe that you want to determine if the EUT is "demodulating" the applied modulated RF field. And you want to measure this at "the terminals of the equipment." You still haven't told us what the EUT is, so I'll use a consumer AM radio receiver as an example. If you apply a modulated RF field, swept over a wide frequency range, the receiver may exhibit both expected (as you cross the operational channel) and unexpected (responses at undesired frequencies). Since you are not trying to verify the resistance to jamming, then we can forget about responses to RF on the Fundamental frequency. So out-of-band signals may create responses in the EUT. And these responses will be presented as audio output (frequently applied to an 8-Ohm speaker). You defined a response criteria of "1KHz signal cannot be higher than -40dBm." The first thing you need to define are the units; dBm is a measure of power, and the system impedance must be defined. Are you talking about dBm in 600 Ohms (audio standard) or in 50 Ohms (RF standard)? -40 dBm in 50 Ohms is +67 dBuV, or about 2.2 millivolts rms. This is an easy measurement for a decent oscilloscope. However, -40 dBm in 600 Ohms is 0.0000001 Watts, which yields a voltage of about 7.7 millivolts rms. Assuming that other noise on this output is very low, you could also do this test with a good rms millivoltmeter. Going beyond this problem, I don't understand what you mean by "trace it against the carrier." This may just be a linguistic perspective problem; perhaps you are trying to say that you need to correlate the measured 1 kHz output with the frequency of the applied field, simply to know what field frequencies produce undesired 1 kHz responses. The easiest way to do this in a manual immunity system is to just stop the sweep whenever you get a response that exceeds your failure criteria and look at the sweep generator displayed frequency. Regards, Ed Ed Price [email protected] WB6WSN NARTE Certified EMC Engineer & Technician Electromagnetic Compatibility Lab Cubic Defense Applications San Diego, CA USA 858-505-2780 (Voice) 858-505-1583 (Fax) Military & Avionics EMC Is Our Specialty This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. IEEE PSES Main Website: http://www.ieee-pses.org/ To post a message send your e-mail to [email protected] Instructions for use of the list server: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] 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. IEEE PSES Main Website: http://www.ieee-pses.org/ To post a message send your e-mail to [email protected] Instructions for use of the list server: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
