Research On Key Technologies Of Photoelectric Hybrid Digital-To-Analog Conversion

With the rapid development of radar,optical communications,and high-end test and measurement technologies,the bandwidth and speed of transmission signals are continuously increasing,and the system imposes higher requirements on the generation and recovery of ultra-wideband and special waveform signals.Digital-to-analog Converter(DAC)is a key device in the above system,which is used to convert digital signals to analog signals.However,due to the electronic bottleneck,the performance of the electronic DAC is further limited.Optoelectronic devices have inherent advantages,such as high bandwidth,low loss and resistance to electromagnetic interference,combining microwave photonics technology to study high-speed,high-precision digitalto-analog conversion devices is considered to be a feasible way to break through the bottleneck of the current technology and has become a research hotspot in the field of digital-to-analog conversion.This paper reviews the development of photonic digital-to-analog converter(PDAC),analyzes the typical scheme of PDAC system,and gives details on the advantages and disadvantages of various schemes.Besides,a new scheme of photoelectric hybrid DAC based on optical-delay interpolation is proposed,the performance parameters of the system are simulated and analyzed,the key components of the system are developed and tested,and a multi-channel photoelectric hybrid digital-to-analog conversion system is built for experimental research.The conversion rate of 4.9152 GSps is obtained at the maximum.Through the deep analysis of the conversion process in a system,the paper demonstrates how the system conversion rates multiply,and explores factors affecting the effective number of bit(ENOB)of the system,the paper deduces the theoretical formula between delay error of single channel,gain mismatch of single channel or the number of system channel,and the ENOB of the system.The theoretical simulation of the above derivation results shows that: a)the system's conversion rate is determined by the number of channels in the system;b)the delay accuracy and gain mismatch of the channel are negatively correlated with the ENOB of the system,and the effect of channel delay accuracy on the ENOB of the system is limited by the frequency of the output signal;c)When the system parameters are determined,the gain mismatch of the channel is the main factor that leads to the decrease of the effective digits of the system.A four-channel wavelength-division multiplexing optical fiber delay line array is designed and completed,and the test results show that the channel delay error is less than ±5ps,which can meet the system experimental requirements.The experimental platform of dual-channel and four-channel photoelectric hybrid digital-to-analog conversion system is established.Through the platform of the system,digital-to-analog conversion experiments on the signals with different frequencies and waveforms are conducted,demonstrating the feasibility of the design scheme and verifying some theoretical simulation results.The conversion rate of 2.4576 GSps and 4.9152 GSps are obtained in dual-channel and four-channel system experiments,and the ENOB of the system reach 4.73 bit and 2.36 bit respectively.Comparing the above experimental results with the theoretical simulation results,it can be seen that the main reason causing the deterioration of the ENOB of the system is that the consistent matching of channels are getting more difficult as the number of system channels increases.Finally,the paper summarizes the photoelectric hybrid digital-to-analog conversion scheme and presents the directions and suggestions for optimizing the photoelectric hybrid digital-to-analog conversion system with high speed and high precision.