  Fast radio bursts are radio transients observed mainly around 1.5 GHz. Their
peak frequency decreases at a rate of 100 ~ 500 MHz/s and some of them have a
broader pulse with an exponentially decaying tail. Common assumptions for fast
radio bursts include a dispersion effect resulting in the peak frequency
drifting and a scattering effect resulting in pulse broadening. These
assumptions attribute the abnormally large dispersion measure and scattering
measure to the environmental medium of the host galaxy. Here we show that the
radiation of fast radio bursts can be explained as an undulator radiation and
the large dispersion measure can be due to a motion effect mainly from the
rotation of the source which is probably variable stars. In our scenario, the
pulse broadening is near-field effects and the pulse itself represents a
Fresnel diffraction pattern sweeping the observer. Our work is the first
analysis of properties of fast radio bursts in the context of a special
mechanism of the radiation instead of a special propagation environment of the
radiation.
