> which means that whatever the impedance actually is, if properly matched, > mismatch losses may be bounded.
Base on the significant electrical length per turns, I cannot see how mismatch losses can be 'bounded' especially at 1GHz. Perhaps at a higher frequency for a much shorter electrical length LAMBDA. > If it were "mismatch loss" wouldn't the > loss be strongly frequency dependent in a periodic fashion? The usual type of mismatch losses is indeed periodic, for resons to do with the defined location of the 'mismatch' or 'physical boundary' in the Tx line. This physical boundary remains the same as the electrical length of the cable changes with frequency. > The losses I > measured increased with increasing frequency, and the nature of the increase > was identical to that specified for the RG-XX coaxial types (with larger > magnitude as previously noted). Speaking off the cuff, (I should expect) the twisting profile (number of twist per unit physical length) would translate to number of 'smooth humps/bumps' per electrical length to decrease as frequency increases. :-) Considering the frequency of interest (80MHz-1GHz in IEC 1000-4-3) there may not be a substantial number of twist per electrical length. Due to the nature of the original intend of the insulation, I expect epsilom_r to be 'resonably' constant. We may not have to deal with the uncertainty associated with the dielectric medium. Making a (hazardous ?) guess, at 1GHz (LAMBDA_0 = 30 cm) LAMBDA= 30 cm/sqrt_epsilon_r Assuming epsilon_r =5 (I believe this will not be an unresonable figure), then LAMBDA=13.4 cm I suppose at a twist rate, say 80 t/meters (having no idea about you cable specs, I pull a figure of approx 12 mm pitch :-) it is roughly 11 or so t/LAMBDA. This will probable be closer to be 'distributed' at 100MHz being then 110 t/LAMBDA. (Ken, I need to corrected my statement I made a few min earlier ...) This I suppose needed some kind of MoM simulation to see the loss characteristics. I would like to hear from anyone handy with a CEM code like NEC, but on some hindsight, the proximity effect of the closely spaced conductors may be a problem for NEC. I suppose at the lower frequency the pair of twisted conductor will start to look like a short circuit at 80MHz. Does anyone out there know of a suitable CEM 'code' or technique to simulate the EM behaviour of such a conductor? I think SPICE is out for this kind of cable. regards, Tim Foo ------------------------------------------- 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"
