In this paper, the electric field radiated by a lightning discharge is derived in the time-frequency domain. By modeling a tortuous and branched lighting discharge, we computed the discrete wavelet transform of the radiated electric field, providing time localization of the fine structure of the field, which is though to be related to the discharge path geometry. By solving the radiated field in the wavelet domain, we aim at simulating the effects of the channel geometry on the victim system.