The RF Channelized Receiver Based On Femtosecond Laser

With development of the technology,the amount of information is constantly increasing and the available communication frequency bands are gradually expanding.The requirements for radio frequency communication is getting harder to meet.As the traditional electronic RF receiving technology cannot satisfy the needs of real-time and high-sensitivity sensing at this stage,how to efficiently integrate photon and microwave technology for the receiver has become more and more popular.Compared with the traditional electric receiving model,the photon-assisted receiver has several advantages:Firstly,the covering bandwidth is larger,which can cover the range of GHz to tens of GHz.This is quite helpful for the perception of signals in the whole frequency band.Secondly,high real-time performance,which can meet the needs of rapid information judgment and timely extraction;Then,high link performance,which can still have a high dynamic range under the conditions of multi-carrier and ultra-wideband;Last but not the least,the power consumption and volume are both smaller than the electronic system.This paper conducts the research on channelized receiving technology based on microwave photonics.With the chirped pulse mixing characteristics,two photon-assisted channelizer depend on different chirp sources are proposed in detail from three perspectives:principle,simulation and experiment.This paper proposes a large-bandwidth,high-performance channelized receiver based on femtosecond lasers.Using a pulse laser and dispersion compensation fiber,the pulse is stretched in time domain and chirped phases are introduced.Then,by introducing time delay into the chirp signal and mixing it with the reference,different local oscillation frequencies can be obtained.Based on the principle of the heterodyne receiver,the target RF signal is down-converted to zero mid-frequency band through the local oscillator of the channel.Combined with digital IQ demodulation technology,the generation of image frequency is further suppressed.Additionally,compared with other channelization schemes such as dual optical frequency combs,this system reduces the difficulty of channel generation,and has the advantages in simple structure and stable performance.In this work,we set up a RF channelized receiver with the bandwidth covering 0-40GHz,the channel width about 1.6GHz and supporting for 25 channels simultaneously.The SFDR@1 Hz of this system is about 100dB.It also has a good crosstalk suppression performance and balanced frequency response.This paper proposes a channelization receiver scheme based on IQ modulator and frequency shift feedback laser.In frequency-shift feedback lasers,CW source is used as the seed light,and the frequency is shifted by the IQ modulator.According to the Talbot effect,this scheme can generate pulsed light sources with discrete chirped phases.Based on the numerical ratio of the closed-loop cavity length to the frequency shift,the repetition frequency of the output pulse sequence can be several times the frequency shift.This article verifies the principle of the IQFSF source from two aspects.In the experiment,IQFSF successfully generated about 60 frequency combs with a frequency interval of 3 GHz.Next,the feasibility of using it as a light source for a channelized receiving system was proved by simulation:by introducing a 1GHz frequency shift,a chirped pulses sequence with a repetition rate of 10GHz was generated.Combined with the chirped pulse mixing characteristics,the RF channelized receiving system is obtained with the bandwidth ranging from 0 to 10GHz,channel width 1GHz,and up to 10 channels.The simulated channelization system has a good performance of side mode suppression ratio greater than 60dB and frequency response error less than 1dB.