This study is to estimate the near-field coupling in mixed digital/RF circuit design for modern high speed electronic systems. The noise source IC is first modelled by physics-based dipole moment model with data obtained from a near-field scanning plane. The victim RF antenna is modelled in full-wave simulation tool and the noise IC is further modelled as Huygens's equivalent source. The tangential fields on the Huygens's box can be calculated by dipole moment model with negligible multiple scattering effect assumption. The noise coupling then can be obtained by surface integration of Poynting vector at the RF antenna receiving port. A full-wave simulation model is first studied to demonstrate the method and a noisy clock buffer IC with victim patch antenna is measured for further validation.