Reserch On Key Technologies Of Microwave Photonic Tunable Receiver

With the increasing demand for large bandwidth and large capacity of electronic systems,traditional electronic receivers have bottlenecks such as narrow operating band,large size,poor tunability,and severe electromagnetic interference,and it has become increasingly difficult to meet future demands.Microwave photonics is well received which combines the large bandwidth processing capability of photonic technology and the fine control advantages of microwave technology well.The microwave photonic tunable receiver solves the bottleneck of electronic receivers.Especially,it has great advantages in large bandwidth processing,and thus has a good development prospect.In this thesis,the key technologies of microwave photonic tunable receivers are studied in to face the future development of electronic systems.The research on linear optimization and image suppression of microwave photonic tunable receivers is carried out.The significance of traditional superheterodyne receivers in electronic systems and clarifies the advantages of microwave photonics is first summarized in this thesis.The technical schemes of microwave photonic tunable receivers at home and abroad are summarized,and the development of key technologies including linear optimization and image suppression technology are summarized.After that,the modulation theory and photodetection theory of microwave photonics are briefly introduced,including key components such as modulators and photodetectors,as well as common modulation methods.the system performance of tunable receiver is theoretically deduced and analyzed.The performance indexes and Influencing factors of frequency conversion gain,noise figure,nonlinear distortion and image rejection are explained in detail.Several optimization schemes for dynamic range and image rejection have been studied as follows:1.After studying the basic idea of linear optimization of microwave photonic tunable receiver,a linearization scheme based on Sagnac loop and phase modulator is proposed.The scheme is embedded in the Sagnac loop using a phase modulator,and characteristics of separate modulation of TE mode and TM mode of phase modulator is used in this scheme.The suppress to the third-order intermodulation interference in the receiver can be achieved by adjusting the polarization state.After simulation analysis,the dynamic range of the system can reach 116.8dB/Hz^4/5,which is better than the unoptimized cascade modulation.The proposed receiver scheme has a dynamic range that is increased by approximately 16dB.2.A DPol-MZM-based linearization scheme of receiver is proposed.This scheme uses an integrated DPol-MZM with introducing an electrical attenuator to control the power attenuation of one RF signal.The third-order intermodulation distortion can be suppressed by adjusting the appropriate polarization state.Through simulation analysis,the dynamic range of the system can reach 111.6dB/Hz^4/5,which is about 11dB higher than the dynamic range of the unoptimized cascaded modulator receiver scheme.3.After studying the basic structure of image rejection receiver,an image rejection scheme based on parallel modulator and optical delay line is proposed.This scheme uses a dimmable delay line to simultaneously tune the optical delay line while tuning the local oscillator,thereby achieving a 90-degree phase shift of the local oscillator signal in the optical domain,avoiding the traditional scheme of phase shifting the high frequency local oscillator signal in the electric domain After simulation analysis,the receiver can suppress the image frequency above 35dB.