| Optical phased array technology is the modern radar technology that combines both microwave technology and photonics technology for controlling a scanning beam of the antenna arrays. Using the phased-array real-delay method, overcome the impact of the aperture effects by increasing signal bandwidth, ability to adapt and meet the demands of high-performance radar of the modern war, and become an important direction of development. Microwave photonic phase shifter is the core part of optically controlled phased array, it arouses general concern in recent years. The abroad in this field have already begun the study of integrated devices. Our research is beginning just based on this background. Si-based Silicon-On-Insulator(SOI) optical waveguide technology and the Si-based micro-electronics devices has been one of the hot topics in the integrated optics because it provides a high index contrast waveguide platform compatible with existing monolithic microelectronic fabrication processes and the inherent compatibility with optical fibers all owing low coupling loss. Our research is beginning just based on this background. We fabricate MWPPS by using SOI, which has good electrical and optical characteristics, and by using Planar Light wave Circuit (PLC) technology. Because of its processes fully compatible with silicon-based CMOS technology, the development of low-cost photonic integrated circuit is one of the important trends, and therefore it is expected to realize the true sense of monolithic integration and give a fundamental resolution of device performance instability, bulky, big weight, high production costs. In addition, the enhancement of accuracy in phase-shifting, reduction of power consumption is also an important task in this issue.This paper firstly resolves the problems of basic structure and function realization. Not like the traditional vector sum analysis, we strictly derivate and demonstrate the phase-shifting function of the devices by combing the basic vector ideas with the carrier modulation, as well we achieve the design conditions for realizing the phase-shift function.The propagating characteristics of photonic phase shifter generated RF signals based on the SOI optical waveguide are simulated by time field domain finite thrust differential method (FDTD) and beam propagation method (BPM). The transmission characteristic of the SOI optical waveguide is simulated. The design rules for SOI single-mode rib waveguide are analyzed, including single-mode condition , coupling efficiency with single-mode optical fiber, capability of confining optical fields and so on. The transferring characteristics of SOI curved waveguides and intersected waveguides are studied. The optimum parameters of the delay line was obtained as follow: H = 5μm, w = 4μm, h = 3.1μm, R> 16mm and the semicircle delay line's bending loss Lbend180<0.1dB.Cosine-type curved SOI rib waveguide was used to form Y branches under the guidance of the mode field matching. The principles of designing large and small angle Y-shaped beam splitter were obtained, and then 1×2 splitter, 2×1 combiner are designed by using cascaded Y-branch. Finally, FD-BPM is used to simulate1×2 splitter and 2×1 combiner. The results show that the average additional loss of EL<0.15dB, output imbalance of IF <0.1dB.The amplitude attenuation units are designed. We use the Multi-Mode Interference (MMI) structure to build variable optical attenuator (MMI-VOA) by using Thermo-optic effect of silicon. With the guidance of classical theory, a 1×1 MMI-VOA on material silica-on silicon of various parameters and variables is designed by BPM waveguide design software. All the simulation results are concluded for orderliness in the period of designing. Here, we use finite element analysis software (FEM: ANSYS Inc9.0) to analysis the thermal response and the temperature distribution. Simulation result indicates that heat-guide layer can significantly increase temperature difference between inner rib area and external rib area. On the other hand, The tolerance analysis indicates that the average temperature variationΔT =300C can make the RI change of inner rib area is 5.2×10-3 respectively, which guarantees the dynamic attenuation is more than 35 dB.The technique of the ICP etching is the key technique to fabricate the microwave photonic phase shifter. This thesis introduces the principle of ICP etching process and equipment working principle in-depth. And we show the effects on the results of the etching by different parameters. We find that the flux of the gas and the duration of the etching are very important to the result of the etching. If the gas flow or etching time becomes larger, the effect of etching is larger too. Contrarily, if flow or time of the protecting gas changes larger, the performance for the protection becomes larger. When the power of the lower electrode plate increases, etching also will be increased, leading to severe corrosion at the bottom side. Adjusting the pressure of the reaction chamber will lead to the change of the etching result. Regularly speaking, if you reduce the reaction pressure, the etching can increase. Also the temperature and etching time can change the etching result. We can finally get the best process parameters to obtain the rib waveguide by quantity experiments.We designed the detailed processes to fabricate microwave photonic phase shifter, and confirmed the optimum parameters of the equipment every step used according to quantity experiments results. Used the scanning electron microscope (SEM) to observe the optical waveguide in various angle and different amplification factor, coupled the optical waveguide with optical fiber and tested the phase shift condition of variable optical time delay line.The study in this paper covers the work of phased array system theory and the theory of RF phase shifter, as well as other related principles and key technologies. This paper provides an approach of shifting the phase of a radio frequency signals and strict mathematical derivation to prove its accuracy and feasibility, and on this basis used the optical communication system simulation tool software of Optiwave Optisystem to do the system simulation, and the simulation results support the theory of derivation The text contained the RF signals shift method, the simulation methods, test methods and test tools, they all provides some useful theoretical and practical aspects of reference for future practical optical phased array radar system design. |
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