Circular waveguide to rectangula waveguide tapper

Hi,
I have to design circular to rectangular tapper. The output of source is from circular waveguide and the instrument input should be fed with rectangular waveguide.
So i have to design a tapper for this conversion. My source signal frequency is of 4.2GHz and in TE11 mode and input to our instrument should be 4.2GHz and TE10 mode.

Can anyone suggest how to design this and what parameters should be considered.
If possible please give some reference which will be helpful for designing this....

This might help you.

http://www.alcatel.hu/bstj/vol44-196...j44-7-1321.pdf

Thanks Mr. CG0210794
I will look after it once...

Dear CG021079,
In the paper that u have sent there was the mode conversion from TE11 to TM11. But I want TE11 to TE01. And i want how to calculate the length of the step inside the tapper and what parameters should be considered in designing it. Can u help by giving some suggestions?

Check this out

https://www.google.com/url?sa=t&rct=...48572450,d.eWU

Thank Mr. CG021079 for ur suggestions. But Iam not fully clarified with these..
I have to search for more...