| Summary: | 碩士 === 國立中央大學 === 機械工程研究所 === 91 ===
Because the people desire to have high quality multimedia communication, frequency division multiplexer (FDM) is always playing an important role in the communication system. By using frequency modulation (FM) for analog video communication system, it would achieve higher signal-to-noise ratio (SNR) and less susceptibility to nonlinear distortion during transmission than by using the amplitude modulation (AM). Besides, analog communication devices like FM transmitters and receivers are much cheaper than the digital communication equipments.
In this thesis, we demonstrate FM/FDM analog video communication system using in-house electro-optic polymer light modulator as light transmitter. We here also used voltage-controlled oscillator (VCO) to modulate signals because of its superior linearity between input voltage and output frequency. Therefore it would produce more accurate desired frequency by controlling input voltage. Moreover we choose phase locked loop (PLL) circuit as our demodulator circuit because PLL has wider deviation range and less sensitivity to noise as compared to other discriminators
The electro-optic polymer light modulator has some characterizations such as low driving voltage and large aperture. By combining Pockels effect from electro-optic polymer material and waveguide coupled of surface plasmon resonance, it is demonstrated that this kind of modulator operated with less applying modulation voltage, less optical insertion loss and easy alignment as compared to other light modulation techniques.
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