The problem, of course, is that your'e trying to filter surge signals (the low frequency components from a 1.2/50us impulse get down to pretty low frequencies) which get close to the frequencies you want to pass. It's extremely difficult to make filters with sharp cut-offs that will handle 6kV impulses and 3000A surge currents (the extreme, but many of the generators are capable of putting out these energies so you need to design for the operator who sets it up that way.) The higher the frequency you want to pass, the more difficult the design.
The other problem is you need enough back impedance to support the desired surge voltage wave. The higher that impedance becomes for the surge wave, the higher it is for the signals you want to pass as well. If the source impedance is 42 ohms (per IEC 1000-4-5), the impedance to the surge wave looking at the coupler input must be much greater than 42 ohms (if it's only 42 ohms for the surge voltage frequencies, you'll only get 50% of the desired surge voltage -- ohms law). Anyway, it isn't simple. If someone does have a good way of increasing the signal frequency capability of the CDN's, we'd like to hear about it. Mike Hopkins [email protected] > -----Original Message----- > From: WOODS, RICHARD [SMTP:[email protected]] > Sent: Wednesday, March 31, 1999 10:05 AM > To: 'emc-pstc'; '[email protected]' > Subject: I/O Surge > > EN50130-4, Immunity for alarm systems, requires that signal lines be surge > tested per EN6100-4-5 using the coupler/decoupler network in figure 12 for > balanced signal pairs. The equipment available on the market has a > bandpass > rating of 100 kHz, and the standard does not specify the type of circuits > to > be used for very high data rates. My question to the community is what > type > of network are you using for Apple Talk (circa 230 KHz) and similar high > speed circuits? > > --------- > 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).
