Research On Key Technology Of Photonic Analog-to-digital Converter In Integrated Transceiver Radio-frequency System

Radio-frequency systems such as future radar develop towards the direction of multi-band,multifunction and integration,which challenges the traditional electronic technology.Integrated transceiver radio-frequency system based on microwave photonic technology has become an important research direction.However,the reported integrated transceiver radio-frequency system based on microwave photonic technology has contradictory requirements on the repetition rate of optical pulses,which leads to sacrifices on working bandwidth and sampling rate of the receiving end.This paper does research on the key technology of photonic analog-to-digital conversion in integrated transceiver radio-frequency system.New solutions are proposed to the high-equivalentsampling-rate analog-to-digital conversion structure based on low-frequency optical pulses,opticalsampling analog-to-digital conversion based on high-frequency optical pulses and the dispersioninduced power fading compensation in photonic analog-to-digital converter.Research focuses on the following three aspects:1)An optical-sampling analog-to-digital-conversion architecture based on optical fiber duplicating loop is proposed.The time delay of optical fiber loop,light source coherence and the type and splitting ratio of optical coupler are studied,through which the performance of the optical-sampling analog-to-digital-conversion architecture based on optical fiber duplicating loop are optimized.For the 5 and 7 times of radio-frequency pulse duplication,avoiding parallel structure,the equivalent 515 MSa/s and 721 MSa/s sampling rates are achieved based on the 103 MHz optical pulses,increasing the equivalent sampling rate and the input bandwidth of the system.2)Time-interleaving optical-sampling analog-to-digital-conversion architecture based on coupled optical-electric oscillator is proposed and researched.Coupled optical-electric oscillator is introduced to provide the system with high-quality optical sampling pulses of low jitter,high repetition rate and narrow pulse width,therefore increasing the sampling rate and working bandwidth of photonic analog-to-digital conversion.The solution is deduced in detail and experimentally studied.Optical pulses with time jitter of 113 fs and repetition rate of 10 GHz are generated with coupled optical-electric oscillator.Optical-sampling analog-to-digital conversion of 1 GHz and 2 GHz radio-frequency signal and band-pass optical-sampling analog-to-digital conversion of 11 GHz radio-frequency signal are realized.3)The problem of dispersion-induced power fading in photonic analog-to-digital conversion system is studied.The power fading compensation scheme based on the polarization multiplexing dual-drive Mach-Zehnder modulator is proposed.Dispersion-induced power fading at 10.4 GHz in photonic time-stretch analog-to-digital converter is compensated,after which the maximum power fading frequency is 0.6 GHz away from the target operating frequency.