V-band gapless OFDM RoF system with power detector down-conversion and novel Volterra nonlinear filtering.

This Letter presents a V-band gapless orthogonal frequency division multiplexing (OFDM) RoF system at 60 GHz employing a power detector to support vector signal down-conversion. Additional RF tone is generated and transmitted from a central station to replace the local oscillator at a wireless receiver for power detector down-conversion. To enhance the spectrum efficiency, the gap between the OFDM signal and the RF tone is not needed. However, the down-converted signal will suffer signal-to-signal interference (SSBI). In this Letter, we propose and successfully employ a novel Volterra nonlinear compensation to mitigate SSBI, resulting in a 22% data rate improvement with a bit-loading algorithm.

Phase transitions in two-dimensional colloidal particles at oil/water interfaces.

Enhanced digital video microscopy is applied to study the equilibrium structure of a two-dimensional charged sulfate-polystyrene particle (2 mum in diameter) monolayer at decane/water interfaces. When the surface density is decreased, a sequential phase transition, pure solid phase-->pure hexatic phase-->liquid-hexatic-coexisting phase-->pure liquid phase, is observed. In addition, the transition between liquid and hexatic phases is first order, while the solid-hexatic phase transition is second order. The temperature effect on this two-dimensional melting transition is discussed by performing the experiments at three different temperatures. The Voronoi [J. Reine Angew. Math. 134, 198 (1908)] construction is applied to analyze the defect structure in the two-dimensional particle monolayer. The pair interaction potential of the two-dimensional colloidal particles is found to be a very long range repulsion and to decay with distance to the power of -3.