Research On Channelization Receiving Tecenology For Broadband Microwave Signals Based On Optical Frequency Comb

With the rapid evolution of high-speed wireless communications systems,internet of things(Io T),new generation of radars and the increasing demand for real-time services,the data has been explosively increased.It is critical challenges and urgent demands for receivers to processes microwave signals distributing from several megahertz to hundreds of gigahertz.Traditional pure electrical methods are constrained by their low bandwidth,expensive and complex systems,which are difficult to cope with instantaneous and wideband signals.In recent years,due to the advantages of photonics technology in terms of large bandwidth,low transmission loss,and immunity to electromagnetic interference,wideband signal processing technology based on photonics has attracted widespread attention and research.In this paper,we first outline the development history of microwave signal receivers and divide the photonics-based broadband microwave receiver into three categories according to previous reported schemes.Then,the key technologies such as the generation of optical frequency comb and optical domain signal processing in channelized reception are theoretically analyzed and mathematical derived.Two types of channelized receiving structures based on optical frequency comb are introduced.According to these two structures,this paper is organized as follows.(1)A coherent channelized receiver based on dual optical frequency comb is designed and simulated.The core of this receiver's front end are two optical frequency combs(OFCs)with different free spectral ranges(FSR).The first comb line of these two OFCs have the same frequency.The local comb lines have different frequency offsets in different channels,which makes the local comb lines can process different spectral components of broadband signal that multicast to the signal OFC.The image suppression down conversion technology is used at the back end of this receiver to avoid in-band spectral aliasing.This receiver's frequency coverage is 20 GHz and has 5 receiving channels and the instantaneous bandwidth of the channel is 4 GHz.The receiver's in-band image rejection ration for wideband and single-tone signal are 15 and 44 d B,respectively.The measurement error of this system is less than 2 MHz and the spurious-free dynamic range is 116d B?Hz^2/3.(2)A wideband and ambiguous-free RF channelizer assisted jointly by comb spacing and amplitude profile of a non-flat OFC is proposed and experimentally demonstrated.In the experiments,five comb lines are generated by phase modulator thus forming 4 receiving channels.Each channel has a receiving bandwidth of 18 GHz and the instantaneous frequency coverage of this receiver is 72 GHz.The measurement error of this channelizer for single-tone is less than 2 MHz and the SFDR is 92d B?Hz^2/3.For three kinds of frequency judgment ambiguity problems encountered in the receiving process,it can be solved by adjusting comb spacing appropriately,which enable ambiguous-free reception over the entire frequency coverage.