Varactor Tuners Eliminated an RF Amplifier
There is an urgent demand for low noise varactor tuners for use in TV receivers to meet the requirements of FCC rules. The RF amplifier has been frequently eliminated in mechanical tuners now in use, resulting in good cross-modulation characteristics and low cost. However, the elimination of the RF amplifier has not been attained in varactor tuners, because of high series resistance of varactor diodes. The series resistance of Si diodes at 470 MHz is around 0.7Ω, and is much higher than that of mechanical capacitor, 0.15Ω. To reduce the noise figure of varactor tuners, tuning diodes with low resistance, i. e. below 0.2Ω must be developed. However, few reports have been published on low series resistance diodes for UHF use.
TV Tuners Using Low Loss and Low Distortion GaAs Varactor Diodes
The noise figure of conventional TV varactor tuners is fairly high, when typical Si diodes, whose average resistance is 0.65Ω at 470 MHz, are used. Low noise tuners which comply with FCC noise requirements can be realized if low loss varactor diodes are developed. However, Si diodes with still lower losses can not be manufactured by conventional Si process technology with high production yield. Low noise Si rf transistors with a noise figure of 1.3 dB at 470 MHz is commercially available. However, noise figure improvement using these transistors at 470 MHz is only 1.0 ~ 1.2 dB when compared with conventional tuners. These low noise Si transistors are high in cost and low in production yield because the specification uniformities are insufficient.
United Nations Convention on the Law of the Sea 1982, A Commentary
Volume VI is the sixth substantive volume to be published in the series. It deals with the work of the First Committee at the Third UN Conference on the Law of the Sea, namely the international seabed area. The volume thus embraces the deep seabed mining regime set out in Part XI of the 1982 Convention on the Law of the Sea together with the 1994 Agreement on its implementation. Completion of this commentary was delayed first by the consultations and negotiations that commenced in 1990 and led to the 1994 Agreement and the entry into force of the Convention. It was further delayed until the Assembly of the International Seabed Authority approved the detailed mining regulations in 2000. Additional supplementary material can be found at UNCLOS 1982 Commentary: Supplementary Documents.