The Study Of The Broadband Phase Tuning And System Application Of Photonic RF Self-interference Cancellation Technology

Co-time Co-frequency Full Duplex wireless communication systems and single-antenna continuous-wave radars both have the problem of insufficient isolation.In the Co-time Co-frequency Full Duplex communication systems,a portion of transmitted signal may be leaked to the receiver because the systems transmit and receive signals simultaneously,which results in self-interference and a series of serious problems,such as the deteriorative threshold sensitivity and the reduced dynamic range in the receiver.In the single-antenna continuous-wave radars,the isolation between the transmitter and the receiver cannot be increased by physical isolation because they share a singleantenna.In order to solve the problem of insufficient isolation in the Co-time Co-frequency Full Duplex communication systems and the single-antenna continuous-wave radars,many solutions have been proposed,among which the RF cancellation technology is the most promising one.However,the performance of the RF cancellation is limited by the operating frequency,the bandwidth and the tuning accuracy of electronic components.Thanks to the large bandwidth,high tuning accuracy and immunity to electromagnetic interference of photonic RF cancellation techniques,the bandwidth,the tuning accuracy and amplitude attenuation in the photonic-assisted cancellation systems have been significantly improved compared.In our work,an in-depth study of photonic RF cancellation systems have been conducted.The main points and the creative results of this thesis are shown as follows:1.The principle of the RF interference cancellation technology is analyzed through the formula deduction and the cancellation performance is evaluated through the concept of cancellation depth.The contour map of the equal cancellation depth is plotted by MATLAB to analyze the effect of amplitude and phase error on the cancellation depth more intuitively,which provides a theoretical basis for the following designs.2.In order to solve the problem of phase change of RF transmitting signal caused by the interface of different materials,a photonic RF cancellation system with phase compensation capability is proposed.A polarization modulator and a dual-parallel Mach-Zehnder modulator are used to build microwave-photonic phase shifters to compensate the phase change and realize anti-phase modulation between the cancellation signal and the leakage signal,respectively.An optical variable attenuator and an optical tunable delay line are applied to match the amplitude and the delay of the signals,respectively.The principles of these two schemes are given and proof-of-concept experiments are conducted to realize the cancellation of the interference signal.3.A photonic RF cancellation system is proposed to eliminate the leakage signal in the single-antenna range radar,which can achieve frequency doubling and elimination of the leaking signal simultaneously.In addition,an optical variable attenuator and an optical tunable delay line are used to achieve equal amplitude and equal delay of signals,respectively.The principles of frequency doubling signal generation and its cancellation are analytically demonstrated.Then,the cancellation system is applied in a single-antenna range radar to eliminate with a target object placed at different positions.