multi-hole directional couplers

Hi,

can somebody help me with design waveguide multihole directional couplers ? Have somebody any theory ?

Thank !

The same theory of two hole and three hole will hold good for multi hole. How ever the band skirt will be the cascaded effect of 3 or 2 hole coupler

Added after 2 minutes:

I forgot to add bandwidth reduction also will affect with multi hole.

Refer book by collin
Foundation of microwave engineering.
He explains nicely.
Also check book by Liao.

Thank to all, in the end i found good book Microwave_Engineering_Pozar

http://www.amazon.com/Microwave-Engi.../dp/0471170968

(or rapidshare :) )

there is about this problem and is the best what I found.

Thank