Abstract
AbstractBased on an optical modulator using the electrooptic effect of lithium niobate (LiNbO3) developed and productized in the UHF band (470 to 770 MHz), a lumped‐constant optical modulator with highly sensitive operation at microwave frequencies has been fabricated and tested and the possibility of realizability has been studied with a view to its application to digital terrestrial television broadcasting. The frequency ranges assigned for program transmission links for the digital terrestrial television broadcasting are 6 to 7 GHz and 10 GHz. Since a broad bandwidth (6 to 9 MHz) is available, various technological challenges must be overcome to assure a high C/N. Therefore, the system of the LN optical modulator and the modulation electrode structures have been fundamentally reconsidered, attaining a C/N of about 25 dB as the target at 6 GHz. When the C/N of the input signal is sufficiently high, the C/N of the present system is determined by the input signal voltage to the LN optical modulator, or the optical modulation index. In a real system, a head amplifier with a gain of 20 dB or greater is inserted. Hence, it is considered sufficiently possible to assure a C/N greater than 45 dB (target value) as a system. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 90(6): 1–9, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20341
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