George Craven was one of the pioneers of
evanescent mode filters and other circuit elements
realized in waveguide below cut-off. He therefore has left
a legacy of very many papers and books on the topic, if
you search on the IN for his name I am sure you will turn
up a lot of data.
I found this, for example:
It discusses the equivalent circuit of the interface
to an inductive section of evanescent waveguide.