Research On Microwave Arbitrary Waveform Generation Technology Based On Light Field Envelope Time Domain Control

For the past few years,with the development of information society,the application of function waveforms have attracted the attention of many researchers.Because the traditional generation of function waveform mainly based on electronic technology,its performance will be restricted by the "electronic bottleneck" of the electronic devices,so that it is unable to adapt to the application demand of the broadband wireless communication,radar and large bandwidth waveform.Microwave photonic technology is an emerging technology,which has advantages of large bandwidth,low loss and electromagnetic interference immunity.So studying the photonic technology to achieve function waveform have a great significance and a high research value.In this thesis,we have analyzed the principles and methods of the photonic microwave arbitrary waveform generation,especially for the microwave triangle waveform,square waveform and sawtooth waveform.The theoretical analysis and simulations are presented in detail,in order to seek the theoretical basis of all kinds of function waveform.According to the existing photonic technology,a novel approach for microwave waveforms generation is proposed,where the scheme is mainly realized on pulse carving and superposition in time-domain.We extend the concept of time-domain synthesis method and optimize the system design.In our thesis work,two single-drive Mach-Zehnder modulators are biased at quadrature point,which are used for pulses shaping.Based on the characteristics of the modulators,a modulated sinusoidal signal is projected onto two orthogonal polarization directions with equivalent proportion.After controlling the time delay between two orthogonal arms of the Tunable differential delay line(TDDL),two optical envelopes are overlapped at the output port of the TDDL and a triangular pulse stream can be synthesized.So only one laser diode(LD)is required for triangular waveform generation and the square waveform is generated independently on another wavelength.In the experiments,a triangular waveform with repetition rate of 3.5 GHz and a 3.5-GHz square waveform can be simultaneously obtained.A 3.5-GHz sawtooth pulse with 50% cycle is generated by pulse carving in time-domain.Furthermore,7-GHz sawtooth(or reversed-sawtooth)signal with full duty cycle can also be generated by utilizing time multiplexing technique.An interesting point is that the superposition of a 3.5-GHz square waveform and the 7-GHz sawtooth waveform contributes the fundamental frequency sawtooth(or reversed-sawtooth)waveform successfully.In the experimental demonstrations,there is no photoelectric convention step for sawtooth waveform generation,and this scheme has not added any additional optoelectronic devices,which saves the experimental cost and extend the application of time-domain synthesis.From the theoretical analysis,experimental demonstration and experimental results,the good performance of this scheme are confirmed.Meanwhile,this research work provides a new idea and direction for microwave arbitrary waveform generation.