Research On Frequency Up-conversion With High Linearity By Using Microwave Photonics

Frequency conversion technology is generally used to achieve frequency up-conversion or down-conversion of microwave signals,and is one of the key technologies of modern wireless communication and radar systems.In recent years,microwave photonics technology has shown great performance advantages and potential application prospects in the field of microwave frequency conversion due to its characteristics of large bandwidth,low transmission loss,high radio frequency isolation,and anti-electromagnetic interference.The related research has been received wide attention and achieved good progress.However,the nonlinear spurious components generated by electro-optic modulation and photoelectric conversion in the process of microwave photonics conversion will limit the spurious dynamic range of the system,thus affecting the performance of the frequency conversion system.In the thesis,the research is carried out to realize the high linearity and large dynamic range of microwave photonic frequency conversion.First,the application background,development history and advantages of microwave photonic frequency conversion technology are introduced systematically;then the operation principle of key optoelectronic devices and the measurement index of the frequency conversion system are given.Next,the system modeling of microwave photonics frequency conversion link is established.By taking the microwave photonic link based on intensity modulation as an example,the influence of the parameters of the main optoelectronic devices on the spurious free dynamic range is simulated.In addition,the impact of the cascaded electrical amplifiers in the front and back end of the microwave photonic link on dynamic range is also analyzed.Based on the theorical analysis,a microwave photonic up-conversion scheme based on carrier suppressed single-sideband modulation(CS-SSB)is investigated.This scheme is optimized through mathematical derivation and simulation,and the frequency conversion experiment setup is established.The measured results show that the 2 GHz IF signal is upconverted to 18GHz,and the spurious-free dynamic range reaches 100.6d B·Hz^2/3.In the communication test,the 16QAM digital signal modulated on 2 GHz carrier is up-converted to18 GHz with the error vector amplitude(EVM)of 2.99%.The results demonstrate that the scheme has outstanding frequency conversion capability and a good spurious free dynamic range.In order to improve the spurious free dynamic range of the frequency conversion system,amicrowave photonic up-conversion scheme actively suppressing the intermodulation components is proposed.It eliminates the third-order intermodulation nonlinear components by optimizing the distribution of radio frequency power and optical power into the parallel dual-drive Mach-Zehnder modulator(DD-MZM)respectively.The operation principle of the scheme is theoretically deduced,the modeling and optimal design are carried out,and the experimental system is established.The measured results show that the spurious free dynamic range of 111.9d B·Hz^4/5 is achieved for the up-conversion of the intermediate frequency signal of 2GHz to 18GHz,which verifies the effectiveness to enhance the linearity of the frequency up-conversion system.