Research On Silicon Based Photonic Broadband DSSS Technology And Application

Microwave photonic technology is widely used in high-speed communication,radar and electronic warfare in recent years for its broadband frequency response characteristics and EMI.Silicon photonics technology is known for small size,high integration,low power consumption and CMOS compatibility,which is a candidate technology for microwave photonic system integration.In this thesis,the key technologies of microwave photonic DSSS based on the silicon photonic technology is studied for ultra-wideband spread spectrum communication.The thesis including the following parts:optical delay line based optical domain spread spectrum technology,photonic matched filter based chip code synchronization technology,and microring filter based interference suppression technology.The main work of this paper includes:1.To break the the bandwidth bottleneck of digital signal processing,the spread spectrum solution process is presented by means of analog optical signal processing.A boardband photonic spread spectrum coding technique based on optical switch and optical delay line is proposed.In the simulation,the radio frequency carrier is 4GHz,and the baseband signal with the information rate of 10Mbps is spread to 2GHz bandwidth(the chip rate is 1Gcps)through the photonic spread spectrum coding technology.2.Aiming at the problem of high-speed chip code synchronization in boardband spread spectrum system,a method based on parallel matched filtering of N optical delay lines was proposed to reduce the synchronization time to NTc(Tc is the chip code bit duration).For a high speed chip code with 1Gcps chip rate and 127 bits code length,the autocorrelation peak can be detected in the optical time domain within one chip period(127ns)in simulation,and the synchronization acquisition is completed.At the same time,it is proposed that the partial matched filter can be realized by reducing the number of parallel channels of the matched filter to simplify the system structure.3.In order to suppress the interference in the boardband spread spectrum bandwidth,the notch filter with microring structure is used.A low-loss double-strip silicon nitride waveguide was used to design the racetrack microring.The specific parameters were as follows:bending radius of 120μm,straight waveguide length of 4mm,and total length of 8.754mm.MZI based coupling region is presented,and the resonant wavelength and coupling coefficient are tuned by heating.Finally,a microring filter structure with interference rejection ratio(extinction ratio)of 21.2dB and filtering bandwidth(FWHM)of 284.6MHz was simulated and realized.The notch filter can effectively improve the performance of the system under the condition of low signal-to-jammer ratio(SJR).In summary,the boardband spread spectrum scheme based on silicon-based photonic integration technology is studied in this paper,which realizes optical domain spectrum spreading,chip code acquisition,and interference suppression in boardband spread spectrum systems.