How to calculate S11 of a patch mounted on a PEC cylinder?

How to calculate S11 of a patchantenna mounted on a PEC cylinder using D-Fdtd? I have read some papers about D-Fdtd method,and it seems that the method could deal with a PEC object but it couldn't deal with a curved piece, is that right?
I have read the Yu's paper[1][2], but in these paper, no particular attention has been paid and no formula is presented for the curved patch. How did the authors deal with the curved patch?

Anyone can help me?

regards
Xu-feng Liu

[1] Application of FDTD Method to Conformal Patch Antennas,Yu, W.; Farahat, N.; Mittra, R., IEEE Antennas and Propagation Society International Symposium, vol.2 ,362_365 , 2001.
[2] Application of FDTD Method to Conformal Patch Antennas,Yu, W.; Farahat, N.; Mittra, R.;IEE Proceedings on Microwaves, Antennas and Propagation, Vol. 148, Issue 3, 218 - 220, June, 2001.