| Broadband wireless access,radar systems,electronic countermeasures,satellite communications,phased-array antennas and astronomical detection are developing to high frequency,large bandwidth and high dynamic range,which pose new challenges to high-frequency signal processing.Microwave photonics technology is considered an effective way to meet the challenges.Phase shifter plays an important role in the above areas,and microwave photonic phase shifter(MPPS)can break through the electronic bottleneck of the traditional phase shifter,due to their low loss,ultra-bandwidth,small size,anti-electromagnetic interference and other obvious advantages.By integrating functions such as phase shifting,frequency doubling,or mixing through microwave photon technology,signal processing can move towards the highfrequency domain,which can better meet the needs of future signal processing.In this paper,some multifunctional phase shifter based on microwave Photonics technology such as a filterless eight-fold MPPS,an MPPS with a tunable frequency multiplication factor(FMF),and a frequency conversion MPPS is studied.The specific research works and innovations are as follows:1.A filterless octave MPPS scheme based on two cascaded MZMs is proposed,which generates two double sideband carrier suppression(DSBCS)optical signals through two cascaded MZMs.Then two optical signals containing 4th-order sidebands are separated by coherent superposition of a 2×2 Optical Coupler(OC).The phase shift is introduced into the two optical sidebands by a phase modulator(PM).After recombination by the second 2×2 OC and then detection by a photodetector(PD),a frequency 8folded microwave signal with phase shift is generated.The feasibility of 360°continuously adjustable phase shift and 8-fold frequency functions were verified through simulation.A continuously adjustable 3600 phase shift can be achieved by controlling the PM’s direct current(DC)bias voltage,and the phase shift is linearly related to the DC bias voltage.2.A full-range MPPS with adjustable FMF is proposed,and two second-order sidebands with 900 relative phase are generated by two parallel MZMs and separated by a 2×2 OC based on coherent superposition.By using a Dual Parallel MZM(DPMZM)modulator to shift the frequency of one sideband,a relative phase shift is introduced into the two optical sidebands by a PM.Combining two beams by the OC,the phase-shifted optical signal is converted to the electrical domain via a PD to generate an electrical signal with a continuously adjustable 360° phase shift and a tunable FMF.The feasibility of 360° continuously adjustable phase shift and FMF adjustable functions was verified through simulation,and the wavelength insensitivity and good tolerance for non-ideal parameters of the system were analyzed.3.A frequency-doubled microwave photonic phase shifter with frequency up-/down-conversion based on DO-DPMZM is proposed.A pair of Single Sideband Carrier Suppression(SSB-CS)optical signals were generated by DO-DPMZM.Then the upper optical path performs up/down conversion on one sideband through DPMZM,while a relative phase shift is introduced between the two optical tones by a PM in the lower path.After combining two beams by the OC and detection by a PD,a frequencyconverted and phase-shifted microwave signal can be obtained.The simulation verifies the two functions of up/down conversion and 360°phase shift of the MPPS.The continuously adjustable 360°phase shift can be achieved by tuning only the DC bias of the PM,and the phase shift is linear with the DC bias.The Electrical Spurious Suppression Ratio(ESSR)of MPPS is higher than 40dB. |
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