Lossless nonuniform transmission lines are synthesized by the method of characteristics in the time-domain. Given m sample values of the time-domain reflection（TDR） response at m time points

the characteristic impedance profile of a lossless nonuniform line represented by m uniform sections can be obtained. The m uniform sections may be different in length

but have a delay time equal to the relevant sample time interval

The propagation velocity of a signal is not necessarily constant along the transmission line. The TDR response is not split into incident and reflective waves

which makes the synthesis method in this paper more simple and efficient than the traditional synthesis methods based on the scattering parameter theory. One synthesis example is given

showing good synthesis accuracy of the impedance profile.