Bob Richards <[email protected]> wrote: List-Post: [email protected] Date: Thu, 8 Jun 2006 13:34:58 -0700 (PDT) From: Bob Richards <[email protected]> Subject: Re: RF Power Amplifiers To: Grace Lin <[email protected]>
I don't believe that formula takes into account the need for 80% amplitude modulation. This will require 5.1dB (about 3.3 times) more power. Other factors, such as room performance and cable losses, need to be taken into consideration as well. Also take into account the need to prevent gain compression, a new requirement in the latest 1000-4-3 standard (always a good idea, now it is explicitly stated). This will require a more powerful amp. It has been my experience that for 80v/m at 3m distance, 500w is a minimum at 80 MHz. This depends to some extent on how high the power can go before gain compression, some amps are better than others. At 80 MHz, there is no magic antenna. :-) Once you get above 200 MHz, there are some large horn antennas that are better than log periodics, but you have to be careful of beamwidth. An antenna with better factors usually means the power is better focused in the desired direction, but this comes at a cost of beamwidth. Also, as you move up in frequency, the power required by the antenna will drop, and the VSWR match of the antenna stays pretty good. However, the cable losses increase at higher frequencies, use good cables and keep them short. A typical lab setup might include a 500 watt amp for 80-200 MHz, and 100w from 200 to 1000 MHz. If you run out of power, you can move the antenna closer (up to 1M from the EUT). For the conducted immunity, 75w is sufficient for tests that I have done with CDNs and EM clamps. If you are required to use a bulk-current injection probe, you might need more power. Bob Richards, NCT. Grace Lin <[email protected]> wrote: Dear Group Members, Please help me to determine specification for RF power amplifiers for 61000-4-3 and 61000-4-6 tests. I found an equation to calculate power required (ETS-Lindgren Antenna Catalog, page 71): PdB(W) = 20 log10 (Edesired(V/m)) +20 log10 (d m) – 20 log10 (fMHz) +AFdB(m-1) +15 Based on this equation, my calculated results are: For 10V/m @ 3m at 80MHz by using ETS-Lindgren 3149 antenna: P(W) = 111.7018 For 10V/m @ 3m at 80MHz by using Schaffner CBL 6140 antenna: P(W) = 22.2874 For 10V/m @ 3m at 1000MHz by using ETS-Lindgren 3149 antenna: P(W) = 12.0016 For 10V/m @ 3m at 1000MHz by using Schaffner CBL 6140 antenna: P(W) = 7.1489 For 10V/m @ 3m at 1GHz by using ETS-Lindgren 3115 antenna: P(W) = 7.1489 For 10V/m @ 3m at 4GHz by using ETS-Lindgren 3115 antenna: P(W) = 4.4681 Do these mean that a 150 watts amplifier is enough for the frequency range 80MHz-1000NHz, and a 10 watts' is enough for the frequency range 1-4GHz? Is a 75 watts' good enough for 61000-4-6 test? Is there any other factors, such as cable loss, etc., that I have to include in the calculation? The measuring system will include a dual directional coupler and a power meter. I have received different recommended specifications. Different specifications mean different prices. The price difference is huge between wattages. Your help is highly appreciated! Best regards, Grace Lin Crestron Electronics, Inc. New Jersey, USA www.crestron.com <http://www.crestron.com/> - ---------------------------------------------------------------- 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 [email protected] 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 [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [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. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] 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 [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
