monopole antenna design in hfss, freq range 30-512 MHZ

i designed a loaded monopole and a helical (normal mode) monopole but both using ADK in hfss 12.1, but still couldn't achieve the bandwidth requirement. what should i do to perfectly design a monopole from 30-512 MHz?

hi
for solve this u should add inductance and resistance to antenna

how to add inductance and resistance to a monopole antenna? can you upload some examples?

draw a plane and define it as RLC boundary condition