To obtain efficient and stable light trapping, angle rotation is introduced to form rotated square pillar array grating (SPAG) solar cells. Compared with the unpatterned stack slab and the optimized uniform SPAG cells, the maximum short-circuit current (Jsc) of the optimized rotated SPAG is increased by 78.54% and 3.21%, respectively. Moreover, besides the fact that the low-incidence angular sensitivity of Jsc could be maintained, Jsc of the optimized rotated SPAG will always be larger than that of the optimized uniform SPAG at any incident angle. Furthermore, when the structural parameters of the subsquare pillar slightly deviate from the optimum, the absorption only deceases slightly as well, which indicates both a high structural tolerance and a stable absorption performance. In addition, our results show not only that the proposed rotated SPAG is promising to make light trapping efficient and stable but also that introducing rotation disorders is promising for other high-absorption pseudounordered surface structures.
Radio-over-Fiber networks providing millimeter-waveband (mm-waveband) signals using wavelength-divisionmultiplexing
techniques are foreseen as the next paradigm to provide broadband wireless access services.Millimeter
wave band operating RoF provides high bandwidth due to its high frequency feature, so it is perfectly adapted to these
system. But a limited cell range with propagation losses leads to frequent handovers when hopping from one remote
antenna units to another causes numerous packet losses strongly, thus to reduce the whole system bandwidth. Moving
cells concept is introduced for avoiding the classical handover time. Nevertheless, frequent switching in optical switches
is inevitable in the resolution which also result in dropping calls. Therefore, a concept of cells extension to allievate the
burden of handover in contral station is proposed. However, since the adjacent RAUs employ the same channel in an
extensive larger cell, co-channel interference exists in the extension scheme. To avoid this, a time slot distributor in the
star-tree architecture of RoF network to support the moving cell extension is proposed and a MAC protocol is designed
for this concept to avoid the co-channel interference.
The simulating technique is used to investigate generating and distributing Ultra-Wide-Band signals depend on fiber
transmission. Numerical result for the system about the frequency response shows that the characteristics of band-pass
filter is presented, and the shorter the wavelength is, the bandwidth of lower frequency is wider. Transmission
performance simulation for 12.5Gb/s psudo-random sequence also shows that Gaussian pulse signal after transported in
fiber is similar to UWB wave pattern mask of FCC in time domain and frequency spectrum specification of FCC in
frequency domain .