  Latest study reports that plasma emission can be generated by energetic
electrons of DGH distribution via the electron cyclotron maser instability
(ECMI) in plasmas characterized by a large ratio of plasma oscillation
frequency to electron gyro-frequency ($\omega_{pe}/\Omega_{ce}$). In this
study, on the basis of the ECMI-plasma emission mechanism, we examine the
double plasma resonance (DPR) effect and the corresponding plasma emission at
both harmonic (H) and fundamental (F) bands using PIC simulations with various
$\omega_{pe}/\Omega_{ce}$. This allows us to directly simulate the feature of
zebra pattern (ZP) observed in solar radio bursts for the first time. We find
that (1) the simulations reproduce the DPR effect nicely for the upper hybrid
(UH) and Z modes, as seen from their variation of intensity and linear growth
rate with $\omega_{pe}/\Omega_{ce}$, (2) the intensity of the H emission is
stronger than that of the F emission by $\sim$ 2 orders of magnitude and vary
periodically with increasing $\omega_{pe}/\Omega_{ce}$, while the F emission is
too weak to be significant, therefore we suggest that it is the H emission
accounting for solar ZPs, (3) the peak-valley contrast of the total intensity
of H is $\sim 4$, and the peak lies around integer values of
$\omega_{pe}/\Omega_{ce}$ (= 10 and 11) for the present parameter setup. We
also evaluate the effect of energy of energetic electrons on the
characteristics of ECMI-excited waves and plasma radiation. The study provides
novel insight on the physical origin of ZPs of solar radio bursts.
