Research On Key Technologies Of Microwave Photonic Radio Frequency Signal Receiver

The receiving technology of radio frequency(RF)signal is a key technology for modern wireless system to obtain information.With the increase of wireless service,the future wireless system is developing towards high frequency,large bandwidth,multifunction and reconfigurable.Due to the electronic bottleneck,the traditional electric RF receiving technology has some shortcomings,such as difficulty in processing cross-band and large bandwidth signals,complex structure for high-frequency signal reception,poor antielectromagnetic interference performance,poor reconfiguration,large volume and weight,etc.It is difficult to meet the development demands of future electronic systems,such as radar,satellite,communication,electronic countermeasures and so on.The RF signal receiving technology based on microwave photonics has the advantages of high frequency,large bandwidth,small transmission loss,strong anti-electromagnetic interference performance,and good reconfigurability,which has an extensive prospect in the future electronic systems.However,microwave photonic RF signal receiver also has some problems to be solved urgently.For example,the image signal received by the antenna will interfere with the useful signal;the nonlinear modulation of the modulator will limit the spurious-free dynamic range(SFDR)of the system;the fiber dispersion will cause power periodic fading of the RF signal;and it is difficult to process large bandwidth RF signal.According to the development demands of future electronic systems,this dissertation studies the above problems.The specific work is as follows:Aiming at the problem of image interference in RF signal receiver,two image-reject microwave photonic down-conversion schemes are proposed and experimentally demonstrated.The first scheme is based on cascaded modulators,where RF signal and quadrature local oscillator(LO)signals are loaded on Mach–Zehnder Modulator(MZM)and polarization division multiplexing Mach–Zehnder Modulator(PDM-MZM),respectively.The phase-cancellation principle is used to achieve image rejection.The experimental results show that the single-tone image rejection ratio(IRR)is higher than 50 d B and the IRR for50-MHz bandwidth is higher than 30 d B.The scheme is suitable for back-to-back application scenario.To meet the application scenario of the antenna remoting and simplify the link structure,the second scheme based on a PDM-MZM is proposed.The scheme uses fiber dispersion effect and microwave photonic phase-shifting technology to eliminate the image signal.It can be tuned to a sub-harmonic down-conversion structure,which can reduce the requirement of the LO signal and save costs.The experimental results show that the singletone IRR is higher than 44 d B in the fundamental and sub-harmonic down-conversion modes,and the IRR for 100-MHz bandwidth is higher than 23 d B.The proposed two schemes do not use optical filters,so the working frequency range is wide and the utilization rate of signal sidebands is high.In addition,the bias points of the modulators can be controlled by commercial bias controllers,so the link is relatively stable.Aiming at the problem of nonlinear distortion in RF signal receiver,two microwave photonic linearization down-conversion schemes are proposed and experimentally verified.The first scheme is based on a dual-polarization quadrantal phase shift keying(DP-QPSK)modulator,where by adjusting the modulation index ratio of the RF signal and LO signal,the thirdorder intermodulation distortion(IMD3)signal power of the two polarization states is equal,and IMD3 is eliminated by using the balanced detection technology.The experimental result show that the scheme can improve the SFDR of the system by 16.43 d B.The scheme does not involve complicated adjustment of polarization state and its principle and operation are simple.To avoid being limited by the common-mode rejection ratio of the balanced photodetector and simplify the scheme,the second scheme based on a dual-polarization binary phase-shift keying modulator is proposed.The scheme uses microwave photonic phase-shifting technology to eliminate the IMD3.The structure only requires a photodetector and it is simple.Besides,the bias points of the modulator can be controlled by a commercial bias controller,so the link is relatively stable.The experimental results show that this scheme can improve the SFDR of the system by 16.51 d B.The proposed two schemes do not use optical filters and digital signal processing(DSP)technology.They achieve IMD3 suppression in the analog domain,so the working frequency range of the two links is wide and the processing speed is fast.Aiming at the problems of low spectral-efficient transmission and periodic power fading in RF signal receiver,a high spectral-efficient transmission scheme based on a DP-QPSK modulator is proposed and experimentally verified.In the scheme,microwave photonic phase-shifting technology is used to compensate for the periodic power fading and realize double spectral-efficient transmission on an optical carrier.The experimental results show that after 25-km optical fiber transmission,when the received optical power is higher than-20 d Bm,two vector signals with the same carrier frequency and different formats can be demodulated correctly.After compensating power periodic fading,the error vector magnitude of quaternary phase shift keying signal can be reduced from 71.58% to 5.88%.The proposed scheme is an all-optical structure,which does not use electric devices and DSP technology,and it has large working bandwidth.It uses a single light source can realize the transmission of two broadband signals,so the structure is simple.Its spectrum transmission efficiency is twice that of the traditional schemes.The signal can be recovered with lower received optical power and the transmission performance is good.Aiming at the problems of large-bandwidth signal processing difficulty and poor reconfiguration in RF signal receiver,a microwave photonic broadband tunable channelized receiving scheme based on Mach–Zehnder Modulators in parallel is proposed and experimentally verified.The scheme uses microwave photonic multi-channel frequency conversion and electric domain filtering technology to realize channel division and receiving of broadband RF signal.The experimental results show that the scheme can realize multiband and large-bandwidth RF signal reception and the working frequency band can be tuned within 10–40 GHz.The single-tone IRR is higher than 55 d B and the channel isolation ratio is higher than 50 d B.The proposed scheme does not use optical frequency comb generation modules and its structure and principle are simple.The RF working range and bandwidth of the scheme can be tuned simultaneously,so the tuning performance is good.The bias points of all modulators can be controlled by commercial bias controllers,so the link is stable.