Broadband Universal RF Photonic Front-end Technology For Integrated Electronic System

The integrated electronic system has the capability of processing broadband,multi-band,multi-beam signals,through utilizing an open and modularized architecture,and can realize multi-functions,such as radar,communication and electronic warfare,with the advantages of reducing the cost and equipment redundancy.As the basis of the integrated electronic system,broadband universal RF front-end technology has received extensive attention and research.However,traditional microwave technology will face the problem of "electronic bottleneck" in terms of bandwidth and electromagnetic interference when utilized to construct a broadband universal RF front-end.Therefore,this paper lays emphasis on the research of the broadband universal RF photonic front-end technology,which is based on microwave photonic technology and utilizes its inherent benefits,such as wide bandwidths,immunity to electromagnetic interference and low loss,to construct broadband universal RF front-end according to the specific appliacation requirements of the integrated electronic system.In this paper,the broadband universal RF photonic front-end is studied in three aspects:high-frequency long-distance transmission,broadband lower-IF reception and multi-channel parallel processing.For the problems of the limited transmission distance,the limited down-converted IF frequency,multi-band frequency conversion and multi-channel RF switching,this paper provides effective solutions effective solutions and have achieved the following innovations:For high-frequency and long-distance transmission applications,aming at the problem of multi-octave signal generation and the chromatic-dispersion-induced power fading power in the broadband universal RF photonic front-end,based on the microwave photonic frequency-doubling up-conversion and dispersion compensation technologies,a broadband universal RF photonic front-end,which is suitable for high-frequency signal generation and long-distance optical fiber transmission application,is proposed.Based on the cascaded structure of a Mach-Zehnder modulator(MZM)and a dual-parallel Mach-Zehnder modulator(DPMZM),frequency-doubling up-conversion and dispersion compensation have been achieved through biasing the MZM at minimum point and adj usting the direct current biases of DPMZM.Experiment results show that,compared with the conventional frequency-doubling up-conversion radio-over-fiber link with cascaded MZMs,the proposed link can matain a flat frequency response at up-conversion output RF frequencies of 11.7-24.7 GHz and 11.5-24.5 GHz for 60 and 80 km fiber link,respectively,with a fluctuation lower than 3.5 dB.At some certain frequencies and transmission lengths,the proposed can achieve about 40 dB improvement in frequency response and 26.7 dB improvement in spurious-free dynamic range(SFDR).In order to solve the problem of signal-signal beat interference in the broadband universal RF photonic front-end when wideband RF signal is down-converted to lower-IF frequency,a broadband lower-IF RF receiver is proposed based on the microwave photonic single sideband(SSB)mixer with two I/Q modulator in parallel and the Kramers-Kronig(KK)detection.The feasibility of the proposed RF receiver is verified by comparing error vector magnitude(EVM)performance of the down-converted IF signal with and without K.K detection.EVM as functions of IF carrier frequency,input LO power,input RF power and coupling ratio between RF and LO paths are measured.Experiment results show that,with KK detection,a 16 QAM signal with a bandwidth of 2.3 GHz and carrier frequency of 20 GHz can be down-converted to a lower IF frequency with a good EVM.Under the measured conditions,when the IF carrier frequency is greater than 1.15 GHz,the EVM value is less than 4.7%.EVM can be improved by more than 9.5%when the IF carrier frequency is close to 1.15 GHz.With the development trend of multi-band and multi-beam satellite communication,aiming at the problems of reconfiguration,scalability and multi-channel parallel processing faced by broadband universal RF photonic front-end technology in the construction of multi-functional integrated satellite communication system,this paper proposes specific solutions for integrated satellite payload system and satellite ground station system respectively.1.Based on wavelength division multiplexing(WDM)technology,microwave photonic SSB mixer and microwave photonic switching technology,a software-defined integrated satellite payload system supporting L,S,Ku,Ka band signal reception is proposed for the first time and a prototype is built.Experiment results show that the proposed integrated satellite payload system has the parallel processing capability of four channels and can be be reconstructed through software to realize the functions of frequency conversion,transpond,broadcast and multicast for L,S,Ku,Ka-bnad signals.The converted IF signals have a frequency around 5 GHz,the gain larger than 10 dB,the SFDR greater than 89 dB Hz2/3 and the phase noise less than-105 dBc/Hz at 1 MHz frequency offset.2.Aiming at the application of satellite ground station system,based on microwave photonic SSB frequency conversion consisting of three parallel optical paths,a low spurious broadband universal microwave photonic mixing front-end is proposed and a prototype is built.Experiments show that the proposed mixing front-end protype can simultaneously realize the down-conversion of RF signals with frequency range of 12-30 GHz and up-conversion of IF signals with frequency range of 2-6 GHz.The conversion gain is greater than 20 dB.The SFDR of down-converted IF signal is larger than 97 dB Hz2/3.As to the up-conversion,the isolation between RF and LO frequency signals is greater than 50 dB.In addition,based on WDM and microwave photonic switching technology,a flexible and scalable multi-channel radio frequency switching system is proposed and a 4×4 microwave photonic switching prototype is built.Experiments show that the prototype of microwave photonic switching system has flexible and scalable capability and has a processing bandwidth of 0.1-30 GHz,a gain of switching link greater than 0 dB,the isolation between outports larger than 70 dB and the SFDR higher than 93 dB·Hz2/3.