Microwave Signal Generation Technology Based On Optical Injection Semiconductor Laser

Synthetic aperture radar(SAR),a high-resolution microwave imaging radar,is a leap of radar imaging technology which has been developing rapidly in recent years.With the continuous improvement of science and technology and the wider application of synthetic aperture radar,the requirement of imaging radar is getting higher and higher,which has prompted us to further improve the resolution of synthetic aperture radar.SAR uses the principle of synthetic aperture to improve the azimuth resolution of radar.The distance resolution and speed resolution can be improved by using a large time-bandwidth product signal.Among various microwave signals based on pulse compression technology with large time-bandwidth products,the linear frequency modulated(LFM)signal is the best choice for SAR systems.At present,most of the methods of generating LFM signals are based on electronics.However,the traditional electronic methods are difficult to meet the requirements of ultra-high broadband,which are limited by the "electronic bottleneck".The technology of LFM signal generation based on microwave photonics breaks through the bottleneck of electrical technology and obtains a large time-bandwidth product with the merits of low cost,anti-electromagnetic interference and other characteristics.However,the current microwave photonics methods also have problems such as complicated systems and non-reusability.In this paper,an LFM signal generation approach based on optical injection semiconductor laser is presented and demonstrated through experiments.Take the advantage of the characteristics of single cycle state in nonlinear dynamic state of optical injection semiconductor lasers: Under the condition that the frequency detuning between the master laser and the slave laser remains unchanged,the frequency of the microwave signal obtained by the beat frequency between the master and slave lasers is linearly changed with the optical injection intensity of the master laser.Using this property,the experimental link is designed in this paper.Through the simulation analysis of the MATLAB software,verify the properties of the nonlinear dynamic state of the optical injection semiconductor laser technology.Plot the spectrum under different injection coefficients.Finally,introduce the characteristics of each dynamic nonlinear state.The LFM signal generation system designed in this paper uses a sawtooth signal and a Mach-Zehnder intensity modulator to modulate the intensity of the main laser's optical signal and then inject it into the slave laser through the circulator.Finally,the LFM signal with time width of 10?s,frequency range of 9.61GHz-16.39 GHz and pulse compression ratio of 67800 is obtained by beating in photodetector.The scheme has the advantages of low cost,large pulse compression ratio,flexible adjustment of center frequency,large time-bandwidth.The high-frequency signal generation can be achieved.It is of great significance to the future radar imaging systems.