Advanced Materials Research Vols. 760-762

Abstract: MIMO and OFDM technology is the core technology of 4G network, and have great development prospects. The main drawback of MIMO-OFDM system is the high PAPR. This paper is based on Cross-antenna rotation and inversion and Active Constellation Extension. The paper proposed the joint algorithm to reduce PAPR in STBC MIMO-OFDM system. It makes use of time, space and frequency freedom to improve the PAPR performance. The simulation results show that the joint algorithm can effectively reduce the PAPR value and do not increase the bit error rate in STBC MIMO-OFDM system.

Abstract: A miniaturized semiconductor micro-ring laser with retro-reflector cavity is investigated. By introducing higher order aspheric terms, miniaturized parabolic mirrors are designed and optimized. A Retro-Reflector based semiconductor micro-ring laser with equivalent radius of 38μm and low threshold current of 60mA is realized. The free-running wavelength is 1541.04 nm when the injection current is increased to 140mA.

Abstract: The availability of atmosphere laser communication systems in dependence on weather conditions and on atmosphere laser link parameters, such as transmitted optical power, beam divergence, or link path distance, is discussed. A number of phenomena in the atmosphere, such as fog, can affect beam attenuation. In this work, the analysis and simulation of the empirical models (like Kruse, Vasseur, etc) indicate that the predicted attenuation of those models is similar and the main attenuation factor of 532nm laser propagation in atmosphere is aerosol particle. Attenuation caused by fog, which can be expressed as a function of the link distance, wavelength, and meteorological visibility, is calculated from visibility data collected at several locations in Guilin. Statistical evaluation of the attenuation caused by fog and the power link margin calculated from atmosphere laser communication link parameters are used for calculating the link availability.

Abstract: Gamma-Gamma distribution model is widely used in studying the impact of the atmospheric turbulence on the Free Space Optical communication systems. This study introduces the Gamma-Gamma distribution model, simulates and studies the spot changes over distance, wavelength, turbulence structure constant and transmit aperture, respectively. Finally, the simulation results show that the Gamma-Gamma distribution is more suitable for middle-strong turbulence than weak turbulence.

Abstract: In order to improve the acquisition probability for laser semi-active terminal correction projectile, the scheme of optimizing launch angle is proposed, the mathematical model of the strapdown seeker laser detector and the capture field model of target is established, and the scheme is verified by Monte Carlo ballistic simulation method. The results show that the scheme of optimizing launch angle improves the target acquisition probability, and will be of important significance to firing table modifying of laser semi-active terminal correction projectile.

Abstract: This paper describes a low-cost DALI system, which can be used to intelligently drive the LED array based on DALI , and can be used in the family field, thus eliminating the high cost of DALI control devices which stop the intelligent lighting system entering household. This article discusses the DALI system master and slave on the hardware & software structure. The innovation lies on communication via GPIO, besides, originally come up with new idea that users can communicate by distinguishing the value in the timer count register between two falling edge if the message is encoded as Manchster . Finally, experiment verified the feasibility of the program.

Abstract: The limitations of current interferogram reduction software with Zernike polynomials in analyzing rectangular interferogram are illuminated. The Zernike polynomials are no longer orthogonal over an rectangular region and have no explicit physical meanings. The reasonable mathematical model for removing translation errors is established based on least squares fitting. The experiment is carried on with a 200mm×75mm aspherical mirror by null-compensation, the misalignment errors can be eliminated from the original phase distribution exactly, thus the accurate surface map is gained, so it provides a guarantee for the superprecision fabrication.

Abstract: From the point of view of quantum mechanics, Harmonic oscillator model was established for analysis of the microscopic mechanism for effect of the laser to the Seed of Erigeron breviscapus (Vant.)Hand.-Mazz. The energy levels of the protein molecule can be reduced by laser radiating seeds which increased the transition probabilities and to advance the activity of the seeds. The protein single non-harmonic oscillator model was built for further research, and the chemical reaction rate formula of protein molecules by laser radiation was obtained. Its explained the laser stimulation and inhibition to the seeds which is the energy unidirectional response.

Abstract: To resolve the limitation of information safety and transmission speed in existing communication system, it applied the modular design method to design optical-electric combined THz wireless communication system framework, and determined 125GHz carrier frequency. Aiming at the core component optical emitter uni-traveling-carrier photodiode (UTC-PD) in THz wireless communication system, it analysed the relationship between output power, bandwidth and input signal types, and determined the emitter bandwidth by experiment. The result shows that the transmission speed in the system is able to reach 3.0Gbps when BER is less than 10^-10.

Abstract: A period-variable grating is designed and fabricated in this paper. The PDMS grating is replicated by method of Si mold which is fabricated by MEMS process. The grating is connected with a mechanical system which can change its pitch when a force is applied, so it can extend the grating and change the grating's period. In the diffraction experiment, about 20% extension ratio of the first diffraction order has been obtained, which will generate the change of diffraction angle of 0.096rad.