iris coupling

traditionally,waveguide filters are made up of several 1/2 lamda resonators coupled with inductive iris or posts.I want to know whether capacitive iris can
be used to couple powers between cavities.
Thanks!

I think it's OK,whether use capacitive iris or reactance iris depend on the coupling cofficient M you need,if you need M to be negetive,I think you consider capacitive iris.You can take a look at <<Theory and design of microwave filters>>Ian Hunter p232-p234

see p510 of the book:
microwave filters,impedance-matching networks,and coupling structures
waveguide filter with shunt-inductance couplings