Conformal antennas require different solvers than full planar structures. There are quite a few solvers commercially available: CST, WIPL-D and HFSS are well known. If you look around on the web using google you can even find open source FDTD and FEM codes for solvers and meshers. It is also possible to calculate/simulate a large number of structures even in multi-layered configuration with or without feed probe analytically and semi-analytically. A good reference about the calculation of conformal antennas is the book: Design of nonplanar microstrip antennas and transmission lines written by Kin-Lu Wong.
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