Phil et al. - On Thu, Jan 05, 2006 at 04:17:44PM -0500, Phil Taylor wrote: > > 50 ohm hard coax makes sharp bends all the time, but it's still 50 ohm. > Reflections do exist but they're way down. This is no doubt because the parts > are designed very carefully. Right. Someone tuned the excess inductance and excess capacitance of the non-coaxial feature to match, so the asyptotic low frequency response is unchanged. That's what proper beveling of the corners of a right angle PC board trace (a.k.a. waveguide) does. When you get down to wavelengths that are similar to the device size, this simple tuning isn't enough, and you need 3-D calculation of S-parameters (or years of experience, or both) to guide the design. > Isn't tuning trace _lengths_ more important on pcbs than what types of corners > you're using? Depends, but usually yes. > Or another way to consider this: Isn't it possible to make a trace that a > certain frequency cannot pass through due to nothing other than its length? If the trace is straight (or at least nearly constant impedance) and the end is terminated correctly, no. - Larry
Attachment:
signature.asc
Description: Digital signature