Research On The Key Technology Of60GHz Radio On Fiber Communication System

Explosive increasing demand of network bandwidth and a more convenient access condition are two drive forces of the study and application of radio on fiber technique. By means of transmitting signals in optical fiber, RoF techniques use big bandwidth of optical fiber, and take advantages of wireless communication such as convenience. The emergence of the antenna array challenges the traditional electronics system, and introducing photonic technology into the array antenna front-end is the key way to solve this challenge. The antenna array combined with photonic technology could not only improve the performances such as bandwidth, SNR and dexterity significantly, but also lay a solid foundation for the optical implementation of signal processing. It has a high application value.Microwave photonic technology applied to the antenna front-end includes optical beam-forming network and photonic phase shifter. The OBFN achieves the control of the spatial distribution of the microwave signal by using optical true-time delay devices to select the relative time delay of each element. It overcomes the beam deflection problems caused by the traditional phase shifter in broadband microwave signal condition. Besides, the high speed data carried on the millimeter wave causes multipath fading and cross interference in RoF system. Controlling the phase in each element of the antenna array is an effective solution, so it’s important to design the high-performance RF phase shifter to control the phase in real-time. Using the optical fiber and other low-cost optical devices is attractive in the design plan.On the basis of the technology studied above, a retro-directive arrays, based on the optical Four-Wave Mixing (FWM) technique, is proposed in this paper. This kind of arrays automatically tracks mobile terminal without phase shifters. Normal self-tracking action is based on phase-conjugating mixing circuit in smart antenna and phased array antenna. We suggest a new method for phase-conjugation which relies on FWM technique to solve the problems in the radio frequency circuit and design the structure of this system afterward. Finally, we analyze the working principle of SOA and design the appropriate parameters to ensure that the phase-conjugating RF signal intensity can make the transmitting antenna array work normally.The creative works in this letter are summarized as follows.The research progress of microwave photonics and working principle of optical wireless communication system is discussed.Introduce application of microwave photon technique in antenna front-end: the working principle of optical beam-forming network and microwave photonic phase shifter. Show the application range and advantages of them. Review the working principle of retro-directive arrays based on phaseconjugating technique. Analysis the problems in this solution, such as the difficulty to make mixers in high frequency and the electromagnetic leakage.Background knowledge relevant to this thesis is briefly discussed including phase conjugating technique based on phase-conjugating mixing circuit, nonlinear effects of semiconductor optical amplifier, the generation of phase conjugate light in SOA.A design for a retro-directive antenna array based on optical FWM technique has been proposed and tested. Using the OptiSystem to carry on the simulation for it.