Research On Technology Of The Signal Acquisition And Generation Based On Photonic Time-Stretch

The acquisition and synthesis of microwave signals play an important role in radar and wire-less communications.Traditional electronic methods are limited by the device bandwidth when acquiring and synthesizing high-frequency,large-bandwidth signals.By utilizing the advantages of photonics,such as large bandwidth,low loss,and anti-electromagnetic interference,the acqui-sition and synthesis of the high-frequency and large-bandwidth microwave signals can be realized.So the study of microwave photonic signal generation and processing has very important applica-tion value.In this paper,the key techniques of microwave signal acquisition and synthesis based on photonic time-stretch technology are studied.The theoretical model of photonic time-stretch tech-nology system is established,and the performance indexes of the system are studied.On this basis,simulation and experiments verifies the theory;a real-time spectrum sensing system is proposed,and the spurious-free dynamic range of the spectrum sensing system is improved by suppressing the third-order intermodulation component of the output signal;the continuous signal acquisition of multi-channel time interleaving is proposed.The program establishes the mathematical mo del of the system,and analyzes the characteristics of the system noise coefficient with frequency,and verifies the performance of the system through simulation and experiment.A dual-channel time-division multiplexed vector signal synthesis scheme is proposed,and the performance of the signal is analyzed.The main innovations and academic contributions of this paper are as follows:In order to have a better understanding of the photonic time-stretch system,a strict theoretical model is established.By separately considering the single-frequency and dual-frequency input signals,the strict expressions of the harmonics and intermodulation components of the system output are derived.Based on this theoretical model,various parameters of the system can be estimated,such as system bandwidth,harmonic power,noise figure,third-order intercept point,spurious-free dynamic range,etc.And the numerical simulations verify this mathematical model.In order to identify and extract spectral information of the microwave signals in wide fre-quency bands,a spectrum sensing scheme using photonic time-stretch is proposed to realize the real-time perception of the input signal spectrum.The stretch factor is 158 and the response time is less than 70 ms.On the other hand,an improved scheme for improving the spurious-free dy-namic range of the system is proposed.By adjusting the light intensity and phase difference of the upper and lower arms of the double parallel Mach-Zehnder modulator,the two parts of the third-order component of the output current of the photo-detector have the same amplitude and opposite phases,so that the third-order intermodulation of the output signal can be suppressed.Through theoretical analysis and experiments,it is verified that this scheme is compared with the single-arm Mach-Zehnder modulation method,and the spurious-free dynamic range is improved by 23 dB.In order to acquire continuous microwave signal with high frequency and large bandwidth,a multi-channel time-interleaved continuous signal acquisition scheme is proposed.The theoretical model of the system is established.Through the theoretical analysis,the special conditions that need to be met during the design of the system are obtained.The relationship between the noise figure and the input signal frequency is studied.A four-channel continuous signal acquisition sys-tem is realized,and the acquisition quality of the analog signal and the digital signal are analyzed respectively.The relationship between the noise figure and the input signal frequency verifies the theoretical prediction.In order to synthesize high-frequency,large-bandwidth microwave signals,a multi-channel time-division multiplexed vector signal synthesis scheme is proposed,and the related system model is established.On this basis,the influence of several key parameters on system performance is discussed.A two-channel time-division multiplexed vector is realized experimentally,and the quality of the synthesized signal is analyzed and discussed.