On Tue, 06 Dec 2005 14:22:31 -0700, Wes Stewart
wrote:


May be, but his link:

http://cp.literature.agilent.com/lit.../5952-8133.pdf

shows exactly what I'm talking about in Figure 3. Note the line
stretcher on one sample port. Because I haven't seen the inside of one
of these I don't know where the coupled arms reside with respect to
each other but the fact that H-P shows the line stretcher tells me
that they must have some (unavoidable, if not purposeful) asymmetry.
They claim 4 degree phase tracking but it's unclear to me whether they
mean the coupled arms with respect to the main line or to each other.

I could be wrong, but I think that 4 deg seems part of the tolerance
of the phase alignment of the two sample ports wrt each other over the
frequency range. Perhaps this is a coupler where the ports are
approximately in phase, and perhaps the line strether is to adjust
phase of forward and reflected ports to create a new reference plane
where it is needed or convenient to the measurement.

Owen
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