Research On Radio-over-Fiber Transmission Techniques For Multi-band Wireless RF Signals

With the development of modern wireless communication techniques, wireless and broadband is considered as the hotspots of entire communications industry. Radio over Fiber technology has both advantages of wireless communication system and optical fiber communication system, with which have good mobility, broad bandwidth and other characteristics. Therefore, using optical fiber to transmit RF signals has been getting more and more attention. Currently, fiber optic repeater system which is the most typical application of RF signals transmission over optical fiber has been used in wireless signals coverage and extended in base station. However, RF optical transceiver is the core component of fiber optic repeater system, and its performance can be directly affected the performance of repeater system and the quality of signals coverage.An ROF system to transmit multi-band wireless RF signals is set up which is usd ADS and Optisystem software. GSM, WLAN, CDMA2000 and WCDMA, the four wireless RF signals are generated by ADS, and then sent to Optisystem which can be simulate optical fiber transmission environment. The received RF signals are downloaded to signal generator, and a spectrum analyzer is used to test the signals quality. At last, the signals are demodulated by VSA89600 and the EVM should be measured to evaluate the performance of the system.In this thesis, an optical transceiver which is used for double frequency band signals transmission is designed. At first, using four PIN diode, anπelectrical modulation attenuator is designed which is used in 800MHz and 2000MHz frequency region. It can change its attenuation according the input signals RF power to achieve ALC function. In the transmitter circuit, we design the transmitter circuit by the form of three-stage LNA cascaded to realize the 800MHz and 2000MHz frequency region RF signal amplify after the PD.