[en] An analysis is presented which describes the nonlinear response of the electrons in a weakly ionized plasma to superposed time-dependent electric fields. Two or more uniform fields with frequencies ω+nΩ, where ωvery-much-greater-thanΩ and the n are small positive and/or negative integers, are considered. A method of calculating the current density is developed which is based upon solution of the Boltzmann equation by use of a single Fourier series in a quasiperiodic approximation. Measurement of the amplitude and phase shift of the nonlinear current density at frequency ω is proposed as a diagnostic technique