No abstract

To improve the output power of a photomixer used as a THz source, we propose a four-leaf-clover-shaped antenna structure composed of a highly resonant radiation element and a stable DC feed element. The resonance characteristics of the proposed structure were first investigated on a half-infinite substrate as a simplified radiation environment to reduce the computation time. Based on the antenna characteristics on that half-infinite substrate, the antenna structure was designed to have a maximum total efficiency and a maximum directivity on an extended hemispherical lens. The input resistance of this structure was six times that of a full-wavelength dipole, significantly improving the mismatch efficiency between a photomixer and the antenna. The terahertz output power from this structure is expected to be 2.7 times that of a full-wavelength dipole.

No abstract

using is installed with the single-port Myrinet cards. It may be another reason why we can see the efficiency decreases when both processors on a node are involved in the simulation.As the number of processors increases in the simulation, the simulation time for each step decreases and each processor will communicate with its neighbors, hence, a heavier burden will be pushed on the networking system. Although the data passing amount decreases when the number of processors is large, each processor will establish the communication with its neighbors frequently; therefore, networking system will become a bottleneck of simulation for both the Myrinet and Ethernet, and consequently, the efficiency of the parallel processing will decrease dramatically. Though we did not present the efficiency of a parallel 3-D FDTD code in this communication, the efficiency of a parallel 3-D FDTD code is 30% lower than the BOR-FDTD due to heavier data passing and more delay in the 3-D case. CONCLUSIONSIn this communication, we have investigated the efficiency of the BOR-FDTD code on a PC cluster using two typical networking systems. Numerical experiments have demonstrated that the efficiency of a parallel code strongly depends not only the method and code structure but also on the type of networking system. A reflector antenna is used to verify the parallel code we developed. REFERENCES

No abstract