  Jitter radiation, the emission of relativistic electrons in a random and
small-scale magnetic field, has been applied to explain the gamma-ray burst
(GRB) prompt emission. The seed photons produced from jitter radiation can be
scattered by thermal/nonthermal electrons to the high-energy bands. This
mechanism is called jitter self-Compton (JSC) radiation. GRB 100728A, which was
simultaneously observed by the Swift and Fermi, is a great example to constrain
the physical processes of jitter and JSC. In our work, we utilize jitter/JSC
radiation to reproduce the multiwavelength spectrum of GRB 100728A. In
particular, due to JSC radiation, the powerful emission above the GeV band is
the result of those jitter photons in X-ray band scattered by the relativistic
electrons with a mixed thermal-nonthermal energy distribution. We also combine
the geometric effect of microemitters to the radiation mechanism, such that the
"jet-in-jet" scenario is considered. The observed GRB duration is the result of
summing up all of the contributions from those microemitters in the bulk jet.
