Research On Key Technologies Of Fiber Delay Line Based On Optical Phased Array Radar

The phased array radar is a kind of radar using phased array antenna, and the radarcould accurately change the amplitude and phase information of the antenna radiatingelements in terms of electronic control. After introduced into the phased array radar, thedelay phase shift technology could overcome the antenna beam deflection signalbroadening phenomena and it greatly expands the instantaneous signal bandwidth of theradar.Firstly, According to the optical phased array radar sub-array mathematical model,the relevant mathematical formulas of the optical phased array radar is derived. Andthen the radar beam pattern, whose frequency varies in X-band, is simulated on theMatlab platform. After that, we have a brief analysis and explanation of the advantagesand significance of the optical phased array radar by the pattern. The noise sources andformulas of the device in the fiber delay line link is analyzed. And a microwave IM/DDdirectly-modulated transmission link model is presented, including a comprehensiveanalysis of all kinds of noise in the transmission link. By calculating we get the result,which suggest that the gain of the delay line link is11.83dB and the noise figure of thefiber delay line link is18.86dB. At the same time, the noise figure is also analyzed byusing different parameter, And we found that many parameters will affect the noisefigure of the link, such as the frequency of the radar signal, the RIN, resistance andcapacitance of the laser, the resistance and capacitance of the PIN and so on. Moreover,through the simulation of a12-element linear array noise pattern figure illustrates thelink of fiber delay line noise that could cause the rise of the beam sidelobe level of thephased array antenna. And the performance of the radar beam will be seriously affectedif the SNR of the link is less than15dB.Then, the pattern function with amplitude and phase errors is derived according tothe phased array theoretical formula. By substituting the fiber delay line data into thepattern, we have a statistical probability analysis of the antenna beam’s performance，and then some relevant theoretical formulas are achieved. The operating frequency ofthe radar is set as10GHz, fiber delay line delay accuracy range is set from1ps to10ps, where the step is0.1ps. After having an analysis on the theoretical formula simulationresults, We found that the antenna beam pointing will offset and the gain will decreasedbecause of the delay error and meanwhile the antenna sidelobe level will rise because ofthe amplitude error. At the same time, compared the numerical results with thesimulation results, the reliability and availability of data is confirmed. Finally, the planarrectangular phased array model is established based on the basic theory. The pattern of12×12planar phased array is simulated on the Matlab platform, while the operatingfrequency is10GHz and30GHz, the range of fiber optic delay line delay accuracy is setfrom0to5ps and step as0.5ps. Then we multiple sample the maximum point and thefirst sidelobe level of the patterns. After deal with the data that achieved before, wefound that the impact of the performance of the planar phased array beam caused by theerrors of the fiber-optic delay line is similar with the linear array.