Wide Bandwidth Microwave Photonic Phase Shifter

Microwave photonics is an interdisciplinary area that studies the interaction between microwave and optical signals,for applications such as broadband wireless access networks,sensor networks,radar,satellite communications.Compared with the traditional microwave signal processing techniques,microwave photonic has advantages such as realizing high bandwidth,overcoming the inherent bottlenecks of electronic techniques,low loss and immunity to electromagnetic interference.Therefore,microwave photonics will own a bright application prospect in the future.In this thesis,we propose two photonic microwave phase shifters based on an integrated dual-polarization dual-parallel MZM and based on a dual-parallel MZM,respectively,and it mainly consists the following contents:(1)A novel wideband microwave photonic phase shifter has been presented.It is based on biasing an integrated dual-polarization dual-parallel Mach Zehnder modulator in the way to generate an orthogonally polarized optical carrier and single RF modulation sideband,and controlling the DC voltage into a polarization dependent optical phase shifter to introduce an optical phase difference to the two orthogonal polarization components.The new photonic microwave phase shifter has a simple structure.It only requires controlling a single DC voltage to obtain an RF signal phase shift.It is suitable for realizing multiple RF signal phase shifts that is required in beamforming applications and the phase shifting operation can be controlled in a remote location.Experimental results are presented which demonstrate the realization of a continuously tunable-180? to 180? phase shift with little amplitude and phase variations of less than ?1.2 dB and ?2°,?1.8 dB and ?4.5°,?2.2 dB and ?6.5° over 0.5-9 GHz,2-26.5 GHz,4-40 GHz frequency range,and a linear RF signal phase shift to control voltage relationship.(2)A wideband microwave photonic phase shifter implemented based on a special dual-parallel Mach-Zehnder modulator(DP-MZM)consisting of two sub-MZMs and a polarization rotator is proposed and demonstrated.A microwave signal to be phase shifted is applied to the two sub-MZMs via a 90? hybrid coupler,to generate two orthogonally polarized intensity-modulated optical signals,which are combined at a polarization beam combiner.A phase-shifted microwave signal is obtained by detecting the combined signal at a photodetector.The tuning of the phase shift is realized by tuning the DC bias voltages applied to the sub-MZMs.Since the phase shift tuning is done electrically,high speed phase tuning can be implemented.The proposed phase shifter is experimentally demonstrated.A continuous phase tuning from 0? to 360? with small magnitude variations of less than ?1 dB and small phase variations of less than ?2.5? in a decade bandwidth from 2.5 to 25 GHz is realized.