Based On The Secondary Light Modulation Uwb Radio System Of Frequency Conversion Technology Research

In recent years, how to improve the rate of wireless communication systems has been an important field of communication research. According to the Shannon theorem, the bandwidth of the communication system with a limited signal-to-noise ratio is up to the bandwidth of the channel, so broaden the carrier frequency is an effective means to improve the communication rate. The space loss of the carrier frequency in wireless communications is increasing with frequency getting higher; and the effect of electromagnetic radiation to the human body has not been determined, the high-frequency wireless communication system using a distributed antenna has become common to reduce communication radiation technology. In densely populated areas, how to maintain communication between a huge number of microwave antennas and base stations known as an urgent task, and radio-over-fiber architecture is a potential scheme to reduce the expenses of distributed antenna system in the future. In radio-over-fiber architecture, microwave antennas and base stations connected with fiber, the expenses of high frequency transmission circuit maintenance had been eliminated, the transmission distance had been increasing and safety had been improved.In this literature a ultra-wideband wireless optical modulation system to receive wireless signals in the3GHz-10GHz range had been designed and completed which use the scheme that combines microwave amplifier circuit and electro-optical modulator. Two method to achieve electro-optic modulator bias, optical and electrical methods, had been studied and two different optical bias methods had been simulated, some theoretical results had been calculated, then a circuit in order to control the LiNbO3Mach-Zehnder electro-optic modulator’s bias voltage which based on the mixed-signal microcontroller C8051F020had been manufactured, the control circuit could be real-time monitoring and classification adjustment. A RF front-end conversion and amplification circuit which use in the ultra-wideband wireless optical modulation system has been designed and producted, the circuit used the double-conversion superheterodyne receive scheme, part of the device has been tested independently to verify the feasibility of the scheme. Finally, the entire wireless receive optical modulation system has been test in separation and overall, the test in the band3GHz-10GHz of the RF front-end system proved that receive of the system with wireless signal-50dBm to-90dBm power could be achieved; by simulating space propagation conditions, the reception of the transmit signal which in both20dBm and30dBm had been tested working smooth; and the ability of the system to accept100Hz low-frequency amplitude modulation signal had been tested.