Applied Mechanics and Materials Vols. 543-547

Abstract: It is aimed at reducing the amount of calculation by 4-point average method, replacing coherent integration with circular correlation and Doppler shift searching with the circumference shift coming from FFT results. It uses two DDR2 caches to store FFT results of receiving yards and local codes. It elaborates the specific implementation methods of this algorithm on FPGA in detail, and stimulates the direct P-code acquisition algorithm based on FFT on ModelSim. The results of stimulation show that the algorithm can improves the data utilization rate and save the acquisition time.

Abstract: Based on the existing contour tracing image recognition technology, combining the embedded system technology and the computer storage control technology, the author makes an integrated design, adopts the image processing chip, USB controller, the imaging sensor and other hardware circuits and develops an intelligent image system. The system can make real-time monitoring the size and change of millimeter-sized irregular target objects. Its applicable value in the fields such as intelligent monitoring of oil equipment, medical imaging and criminal investigation is very high.

Abstract: S.K.Pal's fuzzy set theory has been used to deal with the degraded image, wherein the image edges are uncertain and inaccurate. But Pals algorithm losses low grey level information of the original image and the grayscales of the image can not be extended. A fuzzy image enhancement based on linear membership function is proposed through the analysis of classical Pal's fuzzy enhancement. This algorithm avoids the lost of low grades information of the image as well as increases the image's whole grey scales. It is very suited for low grades, low contrast images such as X-ray images. As a result of the linear transformation comparing with Pal's non-linear scheme, the image processing speed is also improved. Experiment results show that the proposed method outperforms traditional Pal's in terms of contrast stretching effect and speed.

Abstract: To solve the problem that conventional beam forming fails to give full play in suppressing interference of vector sensor array, a new method of beam forming for vector sensor array was discussed based on signal subspace projection. The method projects array manifold matrix on the signal subspace derived from HOSVD, resulting in a spatial spectrum computation method, which could eliminate noise better and generate a lower side lobes. Further theoretical derivations and simulation experiments have verified the effectiveness of this method.

Abstract: Simulated for OFDM system modulated by 16PSK, 16QAM and 64QAM, and then we compared and analyzed their performance in the Rayleigh channel and 2 paths Rayleigh channel. Simulation results show that under the same conditions, Bit Error Rate (BER) of MQAM modulation system is lower than the same order MPSKs

Abstract: For multi-receiver synthetic aperture image formation, if one or more receivers are failed because of unexpectable reasons, the synthetic virtual array may have to be pulled out from operation due to unacceptable pattern distortion. Here, a technique is presented for reconstructing the signals of failed receivers before synthetic aperture image formation. Its performance is validated by using simulated data, as well as real data collected by ChinSAS-150.

Abstract: The echoes of pulse radar from maneuvering targets are amplitude modulation and frequency modulation (AM-FM) signal. At present, the methods of estimating parameters of AM-FM signal are time-frequency analysis method, empirical mode decomposition and empirical wavelet transform based adaptive data analysis methods. This paper takes the idea of intrinsic mode function in guessing the initial phase, and applies the newly developed sparse time-frequency analysis method in AM-FM signal parameter estimation. Simulation results show that the estimating performance of this method in AM-FM signal is good under different SNR and it has low computational cost, and this method is applicable in target acceleration and velocity estimation.

Abstract: A CAN signal capture and analysis system is developed in this paper, which is based on the CAN bus disturbance generator and computer oscilloscope. The main work of this paper is to design the computer software. The software is designed to capture and disturb any CAN signals, and display the waveform on the computer screen. Meanwhile, the software decodes and analyzes the CAN message according to the CAN protocol. A detailed hardware platform building and computer software designing are described in this paper.

Abstract: Communications satellite payload directly determines the performance of the satellite. In this paper, we focus on these advanced satellite communications systems of representative: WGS, MUOS and AEHF, including function and structure of the payload. Then the development trend of communications satellite payload is analyzed. Some suggestions for the development of China's communications satellite payload are proposed at last.

Abstract: The outage probability (OP) of dual-hop fixed-gain amplify-and-forward (AF) relay over Rayleigh fading channels is analyzed when the feedback delay, the estimation error and the multiple co-channel interferences (CCI) are all present. A closed-form expression for the OP is derived and validated by Monte Carlo simulations with several scenarios considered, also the impacts of feedback delay, estimation error and CCI have been shown in the numerical results.