Research On Photonic Generation Technology Of Millimeter Wave Noise With High Excess Noise Ratio

As a typical test and calibration equipment,by inputting accurate and known noise to the communication system and the device under test,the noise source can detect the ability of the communication system to transmit and receive signals and analyze the performance of the device under test.Noise sources play an important role in communication,radar,terahertz imaging,military and other fields.With the rapid development of science and technology and the increasing demand for spectrum resources,many system applications and device development are developing in the direction of high power and high frequency bands.Therefore,the broadband millimeter-wave noise with controllable high excess noise ratio generation technology is not only the key to the development of millimeter-wave noise sources,but also the focus of current research.At present,due to the limited operating frequency and power of electronic devices,the excess noise ratio of noise source developed based on electronic methods is usually less than20 dB.The bandwidth and frequency of the noise sources cannot be controllable.As the frequency increases,the loss of noise power increases,and the difficulty of the manufacturing process increases.Aiming at these problems of the electronic method,this thesis studies the generation of millimeter-wave noise signal based on the photonics method by taking advantage of the high speed and low loss of photons.The main research contents of this thesis are as follows:（1）Theoretical analysis of millimeter-wave noise signals with high excess noise ratio based on photonics.According to Wiener Sinchin’s theorem and Fourier transform,spectrumto-electrical spectrum mapping is realized,and the power spectral density of the generated noise signal is estimated.According to the definition of excess noise ratio,the relationship between excess noise ratio and noise power spectral density is analyzed,so as to obtain the influencing factors of the excess noise ratio.（2）On the basis of theoretical analysis,numerical simulation of the methods of direct photoelectric conversion of broadband ASE optical noise source,single-channel filtering and beat-frequency photoelectric conversion after dual-channel filtering to generate millimeterwave noise signal are carried out by Optisystem simulation software.The simulation results of noise signals generated by different methods are analyzed,which lays the foundation for further experiments to generate millimeter-wave noise with high excess noise ratio.（3）According to the analysis of theory and numerical simulation results,the method of two incoherent optical beat frequencies is selected to generate a broadband millimeter-wave noise with high excess noise ratio.In experiments,a multichannel programmable optical filter is used to filter and shape the ASE optical noise source.The obtained two beams of optical noise with different center wavelengths（frequency）are coupled into the photodetector for beating frequency,thereby generating electrical noise signals.The relationship between the excess noise ratio and its influencing factors is verified by experiments.By selecting the spectral line shape of two beat-frequency noise lights,and adjusting their center wavelength,spectral line width and optical power,under the existing high-speed photodetector response level,a 30-60 GHz noise source with an excess noise ratio greater than 50 dB and a 130-170 GHz noise source with an excess noise ratio greater than 40 dB are experimentally realized.In addition,if a higher-speed photodetector is used,this technology can construct a noise source with a high excess noise ratio in the millimeter wave and even the terahertz band.