problem simulating wave guide from pozar book example

[yefj]

Hello,the hollow waveguide bellow has a=109mm b=43mm L=100mm Er=1
from the formula bellow
For TE21 i get cutoff frequency of 4.4Ghz as shown bellow.
I have defined both port on waveguide ends as shown bellow
but as you can see from simulation result is get m=2 n=1 at cutoff frequency of 2.8Ghz.
Where did i go wrong?
Thanks.

 

[biff44]

not sure what you are simulating. but you seem to have an overmoded waveguide. i.e. the TE20 mode is dominant.

 

[volker@muehlhaus]

The mode picture that you show is TE20, not TE21.

Table from

https://arxiv.org/ftp/arxiv/papers/1201/1201.3202.pdf