"Leon Heller" wrote in message
...
The Elsie filter synthesis program has a bandstop filter design option. I
just tried it and it works OK. None of the designs are top-coupled
resonators, though.

Right... the reason I started down the 'coupled resonator' path was due to
the fact that -- for bandpass filters -- the component values at high
frequencies tend to be much more realizable than with the 'tradition' L-LC,
C-CL structure.

In any case, I've found a paper that addresses the 'unreasonably small
component value' problem -- it interleaves a low-pass filter with the
band-stop filter, and then applies some transformations to get back to a
'reasonable' looking topology. The extra degree of freedom provides a lot
of flexibility in obtaining 'big' component values (at the expense of having
more components involved, of course).

Thanks for the help. I have played with Elsie, and it's a pretty nice
program (even if it does insist on properly scaling its displays only when
its window is maximized! :-) ).

---Joel