I read in !emc-pstc that Chris Chileshe <chris.chile...@ultronics.com> wrote (in <01c249c6.f7fe8500.chris.chile...@ultronics.com>) about 'Designing for low power conducted and radiated immunity' on Thu, 22 Aug 2002:
>1 - I need to let a bit stream through at 25kHz, but reject RF at 150kHz > without a common mode choke (output is not differential). Is this a > tall order? Well, 150 kHz is the 6th harmonic, and you need to preserve at least the 3rd and 5th harmonics to keep some semblance of the data waveform. So, yes, it's a tall order for a simple low-pass filter. But we don't know how much 150 kHz your equipment will actually pick up. 10 V at 150 kHz looks very high unless the cable is very long. Can you use a shielded cable? > >2 - The inductors that give me a reasonable value of impedance at these > sub 1Mhz frequencies tend to be largish and have Self Resonant Freqs. > in the test spectrum albeit some of them (SRFs) are in the radiated >immunity > band where I expect the ferrite to be in charge of attenuation. Is this > likely to cause me problems? Yes, it could do. Inductors with low self-capacitance have to be physically large. > >3 - Can I find a single ferrite that will cover the entire RF test spectrum of > EN 61000-6-2 ( 150kHz - 1Ghz) or is it generally accepted that even the > so called 'wideband' ferrites (SMT 0603/0805 max) are good down to > about 5MHz but no lower? > The latter is the case, especially if you are restricted to SMT parts. You need more volume of ferrite at lower frequencies. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk PLEASE do NOT copy news posts to me by E-MAIL! ------------------------------------------- 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 All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
