Help for civity filter with (n-2) zeros!!!!

[id_guy]

I met the problem as follows.
As you can see from the topic,I saw some filters ,one of whick has N cavities,but realize (N-2) zeros by using cross-coupled sections.
For example,a four cavity filter,I know how to synthesis the filter with one cross section between cavity1 and cavity4 by drawing the circuit in Serenade8.7(the old version of designer). But how to add another cross section between cavity1 and 3 for better rejection?
Hope someone who had got the technique can give me some advise.
How to draw the circuit by certain synthesis software if possible,or recommend some literature about that.
Thx~~~~~~
Regards for the christmas:!:

 

[burton]

A filter with N resonators can produce N transmission zeros (TZs) at most using source-load cross-coupling.A four-pole filter with 1-4 cross-coupling opposite to 2-3 direct coupling can produce two TZs, and can produce 4 TZs if simultaneously using source-load cross-coupling. Whether the filter with 1-3 cross-coupling can produce other TZs depends on the sign of cross-coupling.

 

[id_guy]

I know what do you mean.
But I wonder if you can tell me how to synthesis this :|

 

[id_guy]

God ,noone can do this?