| 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. This technology realized the advantage complementary between microwave technology and photonics technology. It has unique advantages in upgrading radar scanning speed, working frequency, instantaneous bandwidth and scanning accuracy and plays an important role in satellite communications, radio astronomy, space and air control .Microwave photonic phase shifter (MWPPS)is widely concerned and researched as the key device of controlling beam-forming.Domestic's research of this device is in the theory of state for a long time, only a discrete device constructed phase shifter is occasionally reported. The abroad in this field have already begun the study of integrated devices. Our research is beginning just based on this background. This device was studied based on SOI materials, which has good electrical and optical characteristics. By using Planar Light wave Circuit (PLC) technology. and matured Si technology ,Real monolithic integration, low-cost, high stability and high accuracy can be achieved.This dissertation has a full basic research on MWPPS .By combining vector sum technology and carry wave modulation; phase shift function was derived rigorously and improved theoretically. We analysised how to design the device and modulate amplitude for achieving 0-90 degree phase shift. By simulating the phase shift system consisting of discrete component. The function of phase shifting was demonstrated theoretically. Then, the structure of the device was optimized.the aim of optimization is to reduce the size of this device and realize intregration with optoelectronic circuits.In order to realize optical power splitting, Two different structures are used to design splitter.First,large cross section single mode rb waveguides are designed based on singlemode conditionof rib waveguides. cosine type waveguides based on SOI are used to construct Y Branch. The optical propagation characteristics and loss characteristics were simulated by FD-BPM software developed by optiwave Inc.. The results are list as follow: the average excess loss is about 3.15dB, insert loss is 0.2dB and the uniformity is less than 0.1dB. Second, symmetry interference mechanism of multimode interference (MMI) coupler is used to design 1×2 optical splitter.The corresponding simulated results are list as follow: the average excess loss is about 3.24dB, insert loss is 0.25dB and the uniformity is very well . Compared with the two kinds of splitter, their optical propargation characteristics are almost the same such as excess loss, insert loss and uniformity.However,Y splitter is very sensitive to the symmetry of its two branches and MMI-type device is competitive in aspect of compact structure and large tolerance. In the experiment, both Y branch and MMI splitter will be fabricated for further comparison.In aspect of the power attenuator, M-Z type thermo-optical Variable Optical Attenuator was designed theoretically. The strong thermo-optical effect of silicon material is very useful in vary the refractive index. The BPM tool and FEM (ANSYS, Inc.9.0) was used to simulate the optical propagation characteristics and thermo optical response. The results indicated that The dynamic attenuation range from 0.1 dB to about 40dB was achieved by small refractive index variation (0~5.3×10-3).The power assumption is about 57mW and the response time is about 100us, which make the proposed device to be able to operate in the range of about ten kilohertz.Based on the previous theoretical analysis and optimization, we have been obtained the reasonable parameters of the device, which provides a reliable theoretical basis for the latter experiment work. |
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