Thank you PlanarMetamaterials!
If the physical dimensions change with the frequency for which the structure is being solved, it will be resonant at all the frequencies in the 'frequency sweep'. Eg: 3 GHz = Quarter wavelength of 100 mm, 6 GHz = quarter wavelength of 50 mm. So, if the monopole (in this example) shrinks with changing frequency in the frequency sweep, one can get results for different monopoles without designing them in CAD.
I hope this makes more sense now.
Thanks