Directional Loop Coupler

Hi,

I am searching, paper, books etc etc to design, in HFSS or CST, Directional Loop Couplers, like this http://smartdata.usbid.com/datasheets/dsid/62901.pdf (pag 35).

I don't undestand how the 2 SMA and the waveguide coupled and if the second SMA is load.

Then, in detail, where is the network between the 2 SMA and in which way.

Thanks of all...

The coupler looks like this

In the catalog photo, one port is terminated with 50 ohms, the other with a N connector.

Markuvitz, waveguide handbook

http://www.jlab.org/ir/MITSeries/V10.PDF

Tks, this picture is perfect to understand the design, but have u also the dimensions of the structure (i.e. a, b, d, l1 ) ?

I copied the figure from a textbook, unfortunately it has no calculations, neither MIT volume 8, 10 or 11 has it as far as I see.

Basically the loop is interfaced to a standard rectangular waveguide, the loop length is usually < λ/4, the diameter of the round hole and loop distance to waveguide surface determines the coupling coefficients. According to literature, the loop may be rotated by a small angle (e.g. 15 degree).