Research On Ultra Wideband Multi Beam Network Based On Microwave Photonic Technology

In the next generation satellite communication system, satellite loaded platform are developed toward the direction with advanced functionalities such as wideband multi-beam network coverage and multi-channel complex format signal processing. Thus, how to solve the problems of limited signal bandwidth and multi-beam website formation has become one of the most significant issues in satellite communication.The ultra-wideband multi optical beam forming network technology(UWMOBFN), due to its advantages of wide coverage and large channel capacity, is widely recognized as a trend of development of the satellite communication system. The microwave optical technology has the advantages of wide wideband, small volume, light weight, good anti electromagnetic interference performance and so on. If it is applied in the satellite communication system, it can solve the problem of deflection of ultra-wideband multi-beam forming in satellite communication system.In this thesis, basedon the research on the theory of UWMOBFN, the design realization of multi-beam forming network has been performed.Meanwhile, the multi-path interference of wideband multi-beam forming network is also researched. The innovation points of this thesis are as follows:1. The scheme of a transceiver based two-dimensional multi-beam forming network system based on microwave photonics was proposed on the basis of basic theory of beam forming. The fore beam could be produced simulataneouly in the scheme, and the operating frequency in the Ku-band could cover the range of -30 ° to 30 °. The theoretical model of multipath interference was established to investigate waveform distortion and power fluctuation caused by multipath interference, while influence of multipath interference on link performance was studied in the experiment. The results showed that the radio frequency signals demodulated by microwave photonic links was mainly affected by coefficient of interference and interference channel multipath interference.As the increases of the numbers of disturbances, the power fluctuation of the signal increased, but the correlation coefficient decreased.2. The antenna module, the control module and UWMOBFN module were designed. The ultra-wideband optical multi-beam forming network system is developed and tested experimentally. The results showed that phase errors and amplitude error in UWMOBFN were less than ±8.2°and±0.5dB, respectively. Optical beam forming network could work without any shifting at full bandwidth in the full frequency band of 12-18GHz,and the beam offset of each frequency point is below 0.1°, and four independent beams can be formed at the same time.3. Optimiztion scheme of the phase modulation to intensity modulation on filter was proposed to simulate UWMOBFN on phase modulation. It was found that phase modulation to intensity modulation on filter is more suitable for the proposed UWMOBFN. Spurious free dynamic range of system is 74dB, more 7db than the intensity modulation based microwave optical links.