For an in-depth investigation of modern modulation techniques suited for wideband mobile communications, it is necessary to simulate randomly time-variant multipath channels. A time-variant multipath channel distorts a transmission link by frequency and time dispersion. In comparison to the simulation of time dispersion caused by multipath propagation, the simulation of time variations causing frequency dispersions is a rather difficult task. This is due to the time variations of the channel, which are typically very slow compared to the sampling interval of the simulation. Therefore, the focus of this paper is on frequency dispersion. Known methods are reviewed and their disadvantages are discussed. A new way of simulating frequency dispersion is proposed, which is very well suited for time-variant broadband channels.