Development of the sensitizer for generating higher-energy photons under diluted condition via the triplet-triplet annihilation-supported upconversion

It was previously reported that photon upconversion can occur in the solution containing anthracene and the Pt complex of octaethylporphyrin (PtOEP) via the triplet-triplet annihilation process. In this study, by employing the modified Pt complex of the dual anthracene-tethered porphyrin, DA-PtP as a sensitizer, it is demonstrated that shorter-wavelength light can be generated under diluted condition. We synthesized DA-PtP and compared upconversion properties by changing the type of sensitizers. Accordingly, it was shown that the photon upconversion proceeded with the xenon lamp (540 nm) in the presence of DA-PtP. Furthermore, it was found that the emission band in the shorter wavelength light in the near UV region was observed from the solution containing DA-PtP even under diluted condition. From the mechanistic investigation, it was proposed that the anthracene moieties in DA-PtP might inhibit to form agglomeration with the free anthracene. As a result, reabsorption of the higher-energy light generated from upconversion could be suppressed

Study of LEO-SAT microwave link for broad-band mobile satellite communication system

In the field of mobile satellite communications, a system based on low-earth-orbit satellites (LEO-SAT's) such as the Iridium system has been proposed. The LEO-SAT system is able to offer mobile telecommunication services in high-latitude areas. Rain degradation, fading and shadowing are also expected to be decreased when the system is operated at a high elevation angle. Furthermore, the propagation delay generated in the LEO-SAT system is less pronounced than that in the geostationary orbit satellite (GEO-SAT) system and, in voice services, the effect of the delay is almost negligible. We proposed a concept of a broad-band mobile satellite communication system with LEO-SAT's and Optical ISL. In that system, a fixed L-band (1.6/1.5 GHz) multibeam is used to offer narrow band service to the mobile terminals in the entire area covered by a LEO-SAT and steerable Ka-band (30/20 GHz) spot beams are used for the wide band service. In this paper, we present results of a study of LEO-SAT microwave link between a satellite and a mobile terminal for a broad-band mobile satellite communication system. First, the results of link budget calculations are presented and the antennas mounted on satellites are shown. For a future mobile antenna technology, we also show digital beamforming (DBF) techniques. DBF, together with modulation and/or demodulation, is becoming a key technique for mobile antennas with advanced functions such as antenna pattern calibration, correction, and radio interference suppression. In this paper, efficient DBF techniques for transmitting and receiving are presented. Furthermore, an adaptive array antenna system suitable for this LEO-SAT is presented

Ultrafast Hierarchical OTDM/WDM Network

Ultrafast hierarchical OTDM/WDM network is proposed for the future core-network. We review its enabling technologies: C- and L-wavelength-band generation, OTDM-WDM mutual multiplexing format conversions, and ultrafast OTDM wavelengthband conversions