Applied Mechanics and Materials Vols. 568-570

Abstract: An optical fiber based data transmission link for a four-axis gyro stabilized inertial reference system is presented. The operation and configuration of the gyro stabilized platform is introduced to explain the requirement of data transmission. Four passive fiber optic rotary joints (FORJs) instead of traditional electrical sliprings are used to transmit optical signals between these relatively rotating gimbals. The hardware and software design of this optical fiber communication system operated at an updating rate of 1kHz are described to achieve high-speed, real-time, reliable data transmission. The experimental results show that the fiber optic rotary joint-based data transmission link is real-time and reliable. The use of FORJs as fiber optic sliprings will also result in an extremely low friction torque by comparing to electrical slipring assemblies. This allows the system designer to optimize the servo control performance for such high-precision gyro stabilized inertial reference systems.

Abstract: The microwave frequency conversion technology, also known as mixers, RF and microwave system is the transmitter and the receiver have the basic functions. Microwave photon system, instead of the traditional high-speed optoelectronic devices electronic device to overcome the conventional signal processing electronics in the electronic bottleneck. In this paper, respectively, modulators and optical devices based on nonlinear effects of microwave photon frequency conversion methods are summarized, research and verify the bandpass filter can achieve frequency conversion scheme.

Abstract: In order to improve the efficiency of debugging and assembling optical fiber collimator and to facilitate mass production, Automatic assembly technology of optical fiber collimator was studied. A new method was proposed to assemble optical fiber collimator by detecting minimal receiving beam spot. First, the relation was analyzed between the detected spot radius and the distance from the emitting end to reception end according to Gaussian beam transmission theory. Then, an automation system was designed to detect the minimal receiving beam spot when the distance was suitable. The optical fiber collimator was successfully assembled after being fixed. Experimental results show that the coupling loss between two collimators is less than 0.53dB when the wavelength of the transmitting light is 1550nm and the distance between two collimators is less than 1 mm.

Abstract: Navigation message provides receivers with important information about the satellite ephemeris, satellite work status and time systems. Correct navigation message enables receivers to achieve the rapid positioning, time service and other functions. The generation of navigation data is a key part of the GLONASS signal simulator.This paper studies the software part of GLONASS satellite signal simulator and describes the generating process of navigation message in detail. This paper studies the structure of GLONASS signal simulator, focusing on the design and calculation of important parameters of navigation message. After commercial receivers test the output signal from the satellite signal simulator, analysis results show that the navigation message is reasonable in this design method.

Abstract: According to the special communication environment of the underground coal mine and the characteristic of high frequency electromagnetic wave approximation light propagation, this research adopts ray tracing method to simulate and analyze the characteristics of radio wave propagation in the underground roadway. The study not only is the theoretical basis for the development of wireless communication system in the underground, but also will provide an effective guarantee for safe production and modernization superintendence of coal mine.

Abstract: This paper proposes a triple-loop trackingmethod for high-order binary-offset-carrier (BOC)modulated signals. We introduced the characteristics of high-order BOC signals, and then describedthe principle of the triple-loop tracking method, and outlined its framework. The proposed scheme isapplicable to both generic high-order sine- and cosine-phased BOC-modulated signals. The methodremoves the threats brought by the side-peaks ambiguities, while keeping the same sharp correlationof the main peak, thus, allowing for better tracking precision. Simulation results show the validity ofour method in improving the system tracking performances.

Abstract: To improve the objectivity and accuracy of evaluation for electromagnetic environment complexity and its influence on communication equipment, a subjective complexity evaluation method of electromagnetic environment oriented to the communication equipment is presented based on sensitivity and RF protection ratio of communication equipment. Based on statistical concept, the energy correlation factor is modified, and modulation and polarization correlation concept are imported into this method, by which the factor of energy correlation is modified and the subjective evaluation is made by analyzing the time domain correlation, frequency domain correlation, energy domain correlation, modulation correlation and polarization correlation of the electromagnetic environment. These simulation results indicate that communication equipment with various working parameters are influenced differently under the same electromagnetic environment. Namely, the complexities of electromagnetic environment for communication equipment with various working parameters are different.

Abstract: Active phased array antenna (APAA) can realize multi-object tracking and the beamforming is the key technology. Multi-area array and the implement method of its beamforming are introduced in this paper. Coordinated transformation formula is offered based on engineering practice and beams are synthesized by beamforming algorithm of low sidelobe. Following simulation shows results about beam coverage, those provide theoretical basis for the further research.

Abstract: Very minimum chirp keying (VMCK) as a novel high bandwidth efficiency modulation scheme is implemented on small form factor (SFF) software-defined radio (SDR). The VMCK transmission system model is elaborated based on Simulink within Matlab. Also, the final demodulation data stream at the output of the VMCK transmission system shows good performance in simulation. The transmitter and the receiver are designed on the SDR platform. The VMCK baseband signals with 2.5MHz are transmitted from Matlab workspace by ROM block, and then the VMCK signals are ratio frequency (RF) modulated with 432MHz. In addition, the RF receiving intermediate frequency (IF) signals with 30MHz on the SDR platform. The VMCK transmission model is easy to implement and has strong properties to resist synchronization error.

Abstract: Some defects can be found like flat fading, the low transmission efficiency and inter-symbol interference through the analysis of the signal model of SC-FDE system. An integrated solution was proposed by analyzing defect characteristics. The solution merged the technology of SC-FDE into MIMO system. And it used the neural network rake receiver in receiving terminal. The solution chose the weighted parameters in allusion to the differences among the signals of each path, and achieved the maximum diversity gain rates by the adaptive iterative algorithm of neural network. At last the implement logic of this system is described and the simulation is given to demonstrate the improvement of the performance of this system.