Bipolar semiconductor device 2D FDTD modelling suited to parallel computing is investigated in this paper. The performance of a second order explicit approximation, namely the Nessyahu-Tadmor scheme (NT2) associated with the decomposition domain method, are compared to a classical quasi-linear implicit one based on the Alternating Direction Implicit method (ADI). The comparison is performed both from the numerical stability point of view by means of drift-diffusion and energy-momentum simulations and from the computation efficiency point of view. The test structure is a millimetre-wave IMPATT diode the RF as well as internal operation of which is highly non linear. The results demonstrate that high order explicit approximations compete with implicit approximations and allow the development of efficient models well suited to the parallel computation.
This paper proposes a new scheme for the generation and transmission of a MIMO-OFDM signal over optical fiber using a single local oscillator (LO) at 15GHz. This technique is based on subcarrier multiplexing and Optical Carrier Suppression (OCS) modulation using both Dual-Parallel Mach-Zehnder Modulator (DP-MZM) and Dual-Drive Mach-Zehnder Modulator (DD-MZM). DP-MZM is used to multiplex the MIMO-OFDM signals while DD-MZM is used to generate the 90GHz signal by quadrupling. The realistic and global simulation of the complete system is performed to predict the behavior of a Radio over Fiber (RoF) system prior to its realization. The optical and wireless channels are based on Single Mode Fiber (SMF) and TripleS and -Valenzuela (TSV) models, respectively. We have exploited the allocated 7GHz in the 60GHz band for unlicensed use and we have successfully achieved 50km SMF followed by 3m wireless link at 70Gb/s. In comparison with traditional methods, the technique proposed combines better performance at relatively low-cost.
A new time-domain two-dimensional (2D) electromagnetic (EM) physical modelling of non-linear distributed semiconductor devices has been developed. It is based on a numerical procedure which solves in a self consistent manner both Maxwell's equations and a macroscopic transport model based on the drift-diffusion approximation. The software can be run on a parallel computer. It is based on finite-difference time-domain (FDTD) explicit schemes associated to the domain decomposition method. The millimetre-wave travelling-wave IMPATT diode or Distributed IMPact ionisation and Avalanche and Transit Time (DIMPATT) diode is the non linear test structure chosen to validate the model. RF simulations under amplification and CW oscillation operating modes have been performed. The results presented in this paper consist on the one hand of results that can be qualitatively compared to previously published theoretical works and on the other hand of features especially pointed out thanks to the new electromagnetic physical model capabilities.
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